aspirin/chlorpheniramine/phenylephrine (OTC)

Temporary Relief of Common Cold Cough & Upper Respiratory Symptoms

2 tablets fully dissolved in 4 oz of water q4hr; not to exceed 8 tablets/day

Temporary Relief of Common Cold Cough & Upper Respiratory Symptoms

Alka-Seltzer Plus Cold

• <12 years old: Ask a pediatrician
• >12 years: 2 tablets fully dissolved in 4 oz of water q4hr; not to exceed 8 tablets/day

Contraindicated (7)

• abrocitinib

  abrocitinib and aspirin both increase anticoagulation. Contraindicated. Antiplatelet drugs, except for low-dose aspirin (=81 mg qDay), during the first 3 months of treatment are contraindicated.

• dichlorphenamide

  dichlorphenamide increases levels of aspirin by unknown mechanism. Contraindicated. Coadministration of dichlorphenamide with high-dose aspirin may increase salicylate levels. Anorexia, tachypnea, lethargy, and coma reported.

• iobenguane I 123

  phenylephrine decreases effects of iobenguane I 123 by receptor binding competition. Contraindicated. If clinically appropriate, discontinue drugs that compete for NE receptor sites for at least 5 half-lives; may cause false-negative imaging results.

• isocarboxazid

  isocarboxazid increases effects of phenylephrine by pharmacodynamic synergism. Contraindicated. Risk of acute hypertensive episode.

• linezolid

  linezolid increases effects of phenylephrine by pharmacodynamic synergism. Contraindicated. Risk of acute hypertensive episode.

• mifepristone

  aspirin, mifepristone. Other (see comment). Contraindicated. Comment: Aspirin induced antiplatelet activity may induce excessive bleeding after an abortion w/mifepristone (RU 486).

• phenelzine

  phenelzine increases effects of phenylephrine by pharmacodynamic synergism. Contraindicated. Risk of acute hypertensive episode.

Serious - Use Alternative (65)

• abametapir

  abametapir will increase the level or effect of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. For 2 weeks after abametapir application, avoid taking drugs that are CYP3A4 substrates. If not feasible, avoid use of abametapir.

• amitriptyline

  amitriptyline, phenylephrine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.

• amoxapine

  amoxapine, phenylephrine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.

• apalutamide

  apalutamide will decrease the level or effect of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Coadministration of apalutamide, a strong CYP3A4 inducer, with drugs that are CYP3A4 substrates can result in lower exposure to these medications. Avoid or substitute another drug for these medications when possible. Evaluate for loss of therapeutic effect if medication must be coadministered. Adjust dose according to prescribing information if needed.

• benazepril

  aspirin, benazepril. pharmacodynamic antagonism. Avoid or Use Alternate Drug. Coadministration may result in a significant decrease in renal function. NSAIDs may diminish the antihypertensive effect of ACE inhibitors. The mechanism of these interactions is likely related to the ability of NSAIDs to reduce the synthesis of vasodilating renal prostaglandins.

• cabergoline

  cabergoline, phenylephrine. Mechanism: pharmacodynamic synergism. Contraindicated. Additive vasospasm; risk of hypertension.

• calcium/magnesium/potassium/sodium oxybates

  chlorpheniramine, calcium/magnesium/potassium/sodium oxybates. Either increases effects of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Profound sedation, respiratory depression, coma, and death may result if coadministered. Reserve concomitant prescribing of these drugs in patients for whom other treatment options are inadequate. Limit dosages and durations to the minimum required. Monitor closely for signs of respiratory depression and sedation.

• caplacizumab

  caplacizumab, aspirin. Either increases effects of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug.

• captopril

  aspirin, captopril. pharmacodynamic antagonism. Avoid or Use Alternate Drug. Coadministration may result in a significant decrease in renal function. NSAIDs may diminish the antihypertensive effect of ACE inhibitors. The mechanism of these interactions is likely related to the ability of NSAIDs to reduce the synthesis of vasodilating renal prostaglandins.

• clomipramine

  clomipramine, phenylephrine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.

• desflurane

  desflurane increases toxicity of phenylephrine by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of V tach, HTN.
  
  desflurane increases levels of phenylephrine by decreasing metabolism. Contraindicated.

• desipramine

  desipramine, phenylephrine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.

• dihydroergotamine

  dihydroergotamine, phenylephrine. Mechanism: pharmacodynamic synergism. Contraindicated. Additive vasospasm; risk of hypertension.

• dihydroergotamine intranasal

  dihydroergotamine intranasal, phenylephrine. Mechanism: pharmacodynamic synergism. Contraindicated. Additive vasospasm; risk of hypertension.

• doxapram

  doxapram increases effects of phenylephrine by pharmacodynamic synergism. Avoid or Use Alternate Drug. Additive pressor effect.

• doxepin

  doxepin, phenylephrine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.

• eluxadoline

  chlorpheniramine, eluxadoline. Either increases effects of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Avoid coadministration with other drugs that cause constipation. Increases risk for constipation related serious adverse reactions.

• enalapril

  aspirin, enalapril. pharmacodynamic antagonism. Avoid or Use Alternate Drug. Coadministration may result in a significant decrease in renal function. NSAIDs may diminish the antihypertensive effect of ACE inhibitors. The mechanism of these interactions is likely related to the ability of NSAIDs to reduce the synthesis of vasodilating renal prostaglandins.

• ergoloid mesylates

  ergoloid mesylates, phenylephrine. Mechanism: pharmacodynamic synergism. Contraindicated. Additive vasospasm; risk of hypertension.

• ergotamine

  ergotamine, phenylephrine. Mechanism: pharmacodynamic synergism. Contraindicated. Additive vasospasm; risk of hypertension.

• ether

  ether increases toxicity of phenylephrine by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of V tach, HTN.

• etomidate

  etomidate increases levels of phenylephrine by decreasing metabolism. Contraindicated.

• fexinidazole

  fexinidazole will increase the level or effect of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Fexinidazole inhibits CYP3A4. Coadministration may increase risk for adverse effects of CYP3A4 substrates.

• fosinopril

  aspirin, fosinopril. pharmacodynamic antagonism. Avoid or Use Alternate Drug. Coadministration may result in a significant decrease in renal function. NSAIDs may diminish the antihypertensive effect of ACE inhibitors. The mechanism of these interactions is likely related to the ability of NSAIDs to reduce the synthesis of vasodilating renal prostaglandins.

• ibuprofen

  ibuprofen decreases effects of aspirin by Other (see comment). Avoid or Use Alternate Drug. Comment: Ibuprofen decreases the antiplatelet effects of low-dose aspirin by blocking the active site of platelet cyclooxygenase. Administer ibuprofen 8 h before aspirin or at least 2-4 h after aspirin. The effect of other NSAIDs on aspirin is not established.
  
  ibuprofen increases toxicity of aspirin by anticoagulation. Avoid or Use Alternate Drug. increases risk of bleeding.

• ibuprofen IV

  ibuprofen IV increases toxicity of aspirin by anticoagulation. Avoid or Use Alternate Drug. increases risk of bleeding.
  
  ibuprofen IV decreases effects of aspirin by Other (see comment). Avoid or Use Alternate Drug. Comment: Ibuprofen decreases the antiplatelet effects of low-dose aspirin by blocking the active site of platelet cyclooxygenase. Administer ibuprofen 8 h before aspirin or at least 2-4 h after aspirin. The effect of other NSAIDs on aspirin is not established.

• idelalisib

  idelalisib will increase the level or effect of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Idelalisib is a strong CYP3A inhibitor; avoid coadministration with sensitive CYP3A substrates

• imipramine

  imipramine, phenylephrine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.

• isocarboxazid

  isocarboxazid increases effects of chlorpheniramine by Other (see comment). Avoid or Use Alternate Drug. Comment: Isocarboxazid should not be administered in combination with antihistamines because of potential additive CNS depressant effects. MAO inhibitors also prolong and intensify anticholinergic effects of antihistamines. .

• isoflurane

  isoflurane increases toxicity of phenylephrine by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of V tach, HTN.

• ketorolac

  aspirin, ketorolac. Either increases toxicity of the other by pharmacodynamic synergism. Contraindicated.

• ketorolac intranasal

  aspirin, ketorolac intranasal. Either increases toxicity of the other by pharmacodynamic synergism. Contraindicated.

• lesinurad

  aspirin decreases effects of lesinurad by unspecified interaction mechanism. Avoid or Use Alternate Drug. Aspirin at doses >325 mg/day may decrease lesinurad efficacy. Aspirin doses 325 mg/day or less (ie, for cardiovascular event prophylaxis) does not decrease lesinurad efficacy and can be coadministered.

• lisinopril

  aspirin, lisinopril. pharmacodynamic antagonism. Avoid or Use Alternate Drug. Coadministration may result in a significant decrease in renal function. NSAIDs may diminish the antihypertensive effect of ACE inhibitors. The mechanism of these interactions is likely related to the ability of NSAIDs to reduce the synthesis of vasodilating renal prostaglandins.

• lofepramine

  lofepramine, phenylephrine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.

• lonafarnib

  lonafarnib will increase the level or effect of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration with sensitive CYP3A substrates. If coadministration unavoidable, monitor for adverse reactions and reduce CYP3A substrate dose in accordance with product labeling.

• macimorelin

  aspirin, macimorelin. unspecified interaction mechanism. Avoid or Use Alternate Drug. Drugs that directly affect the pituitary secretion of growth hormone (GH) may impact the accuracy of the macimorelin diagnostic test. Allow sufficient washout time of drugs affecting GH release before administering macimorelin. .

• maprotiline

  maprotiline, phenylephrine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.

• measles, mumps, rubella and varicella vaccine, live

  aspirin, measles, mumps, rubella and varicella vaccine, live. Mechanism: unspecified interaction mechanism. Avoid or Use Alternate Drug. Risk of Reye's Syndrome with combination; avoid salicylate use for 6 wks after vaccination.

• methotrexate

  aspirin increases levels of methotrexate by decreasing renal clearance. Avoid or Use Alternate Drug. Caution should be exercised when salicylates are given in combination with methotrexate. Risk for drug interactions with methotrexate is greatest during high-dose methotrexate therapy, it has been recommended that any of these drugs be used cautiously with methotrexate even when methotrexate is used in low doses.

• methoxyflurane

  methoxyflurane increases toxicity of phenylephrine by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of V tach, HTN.

• methylergonovine

  methylergonovine, phenylephrine. Mechanism: pharmacodynamic synergism. Contraindicated. Additive vasospasm; risk of hypertension.

• metoclopramide intranasal

  chlorpheniramine, metoclopramide intranasal. Either increases effects of the other by Other (see comment). Avoid or Use Alternate Drug. Comment: Avoid use of metoclopramide intranasal or interacting drug, depending on importance of drug to patient.

• mifepristone

  aspirin will decrease the level or effect of mifepristone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• mitotane

  aspirin will decrease the level or effect of mitotane by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• moexipril

  aspirin, moexipril. pharmacodynamic antagonism. Avoid or Use Alternate Drug. Coadministration may result in a significant decrease in renal function. NSAIDs may diminish the antihypertensive effect of ACE inhibitors. The mechanism of these interactions is likely related to the ability of NSAIDs to reduce the synthesis of vasodilating renal prostaglandins.

• nortriptyline

  nortriptyline, phenylephrine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.

• pemetrexed

  aspirin increases levels of pemetrexed by unspecified interaction mechanism. Avoid or Use Alternate Drug. Interrupt dosing in all patients taking NSAIDs with long elimination half-lives for at least 5d before, the day of, and 2d following pemetrexed administration. If coadministration of an NSAID is necessary, closely monitor patients for toxicity, especially myelosuppression, renal toxicity, and GI toxicity.

• perindopril

  aspirin, perindopril. pharmacodynamic antagonism. Avoid or Use Alternate Drug. Coadministration may result in a significant decrease in renal function. NSAIDs may diminish the antihypertensive effect of ACE inhibitors. The mechanism of these interactions is likely related to the ability of NSAIDs to reduce the synthesis of vasodilating renal prostaglandins.

• probenecid

  aspirin decreases effects of probenecid by acidic (anionic) drug competition for renal tubular clearance. Avoid or Use Alternate Drug. Aspirin decreases uricosuric action of probenecid.

• propofol

  propofol increases levels of phenylephrine by decreasing metabolism. Contraindicated.

• protriptyline

  protriptyline, phenylephrine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.

• quinapril

  aspirin, quinapril. pharmacodynamic antagonism. Avoid or Use Alternate Drug. Coadministration may result in a significant decrease in renal function. NSAIDs may diminish the antihypertensive effect of ACE inhibitors. The mechanism of these interactions is likely related to the ability of NSAIDs to reduce the synthesis of vasodilating renal prostaglandins.

• ramipril

  aspirin, ramipril. pharmacodynamic antagonism. Avoid or Use Alternate Drug. Coadministration may result in a significant decrease in renal function. NSAIDs may diminish the antihypertensive effect of ACE inhibitors. The mechanism of these interactions is likely related to the ability of NSAIDs to reduce the synthesis of vasodilating renal prostaglandins.

• sevoflurane

  sevoflurane increases toxicity of phenylephrine by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of V tach, HTN.
  
  sevoflurane increases levels of phenylephrine by decreasing metabolism. Contraindicated.

• sodium oxybate

  chlorpheniramine, sodium oxybate. Either increases effects of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Profound sedation, respiratory depression, coma, and death may result if coadministered. Reserve concomitant prescribing of these drugs in patients for whom other treatment options are inadequate. Limit dosages and durations to the minimum required. Monitor closely for signs of respiratory depression and sedation.

• ticlopidine

  aspirin increases effects of ticlopidine by pharmacodynamic synergism. Avoid or Use Alternate Drug. Enhanced risk of hemorrhage.

• trandolapril

  aspirin, trandolapril. pharmacodynamic antagonism. Avoid or Use Alternate Drug. Coadministration may result in a significant decrease in renal function. NSAIDs may diminish the antihypertensive effect of ACE inhibitors. The mechanism of these interactions is likely related to the ability of NSAIDs to reduce the synthesis of vasodilating renal prostaglandins.

• tranylcypromine

  tranylcypromine increases effects of chlorpheniramine by Other (see comment). Avoid or Use Alternate Drug. Comment: Tranylcypromine should not be administered in combination with antihistamines because of potential additive CNS depressant effects. MAO inhibitors also prolong and intensify anticholinergic effects of antihistamines. .

• trazodone

  trazodone, phenylephrine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.

• trimipramine

  trimipramine, phenylephrine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.

• tucatinib

  tucatinib will increase the level or effect of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid concomitant use of tucatinib with CYP3A substrates, where minimal concentration changes may lead to serious or life-threatening toxicities. If unavoidable, reduce CYP3A substrate dose according to product labeling.

• varicella virus vaccine live

  aspirin, varicella virus vaccine live. Mechanism: unspecified interaction mechanism. Avoid or Use Alternate Drug. Risk of Reye's Syndrome with combination; avoid salicylate use for 6 wks after vaccination.

• voxelotor

  voxelotor will increase the level or effect of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Voxelotor increases systemic exposure of sensitive CYP3A4 substrates. Avoid coadministration with sensitive CYP3A4 substrates with a narrow therapeutic index. Consider dose reduction of the sensitive CYP3A4 substrate(s) if unable to avoid.

• yohimbe

  yohimbe, phenylephrine. Mechanism: pharmacodynamic synergism. Contraindicated. Risk of acute hypertensive episode.

Monitor Closely (533)

• abciximab

  aspirin, abciximab. Either increases toxicity of the other by anticoagulation. Use Caution/Monitor. The need for simultaneous use of low-dose aspirin and anticoagulant or antiplatelet agents are common for patients with cardiovascular disease; monitor closely.

• acalabrutinib

  acalabrutinib increases effects of aspirin by anticoagulation. Modify Therapy/Monitor Closely. Coadministration of acalabrutinib with antiplatelets or anticoagulants may further increase risk of hemorrhage. Monitor for signs of bleeding and consider the benefit-risk of withholding acalabrutinib for 3-7 days presurgery and postsurgery depending upon the type of surgery and the risk of bleeding.

• acebutolol

  acebutolol and aspirin both increase serum potassium. Use Caution/Monitor.
  
  aspirin decreases effects of acebutolol by pharmacodynamic antagonism. Use Caution/Monitor. Long term (>1 wk) NSAID use. NSAIDs decrease prostaglandin synthesis.

• aceclofenac

  aceclofenac and aspirin both increase anticoagulation. Use Caution/Monitor.
  
  aceclofenac and aspirin both increase serum potassium. Use Caution/Monitor.

• acemetacin

  acemetacin and aspirin both increase anticoagulation. Use Caution/Monitor.
  
  acemetacin and aspirin both increase serum potassium. Use Caution/Monitor.

• acetazolamide

  acetazolamide, aspirin. Either increases levels of the other by Other (see comment). Use Caution/Monitor. Comment: Carbonic anhydrase inhibitors (CAIs) and salicylates inhibit each other's renal tubular secretion, resulting in increased plasma levels. CAIs also shift salicylates from plasma to the CNS, leading to potential neurotoxicity.
  
  acetazolamide, aspirin. Mechanism: passive renal tubular reabsorption due to increased pH. Use Caution/Monitor. Salicylate levels increased at moderate doses; risk of CNS toxicity. Salicylate levels decreased at large doses (d/t increased renal excretion of unchanged salicylic acid).

• agrimony

  aspirin and agrimony both increase anticoagulation. Use Caution/Monitor.

• albuterol

  albuterol and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  chlorpheniramine increases and albuterol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  aspirin increases and albuterol decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  albuterol and phenylephrine both decrease sedation. Use Caution/Monitor.

• alfalfa

  aspirin and alfalfa both increase anticoagulation. Use Caution/Monitor.

• alfentanil

  alfentanil increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• alfentanil

  chlorpheniramine and alfentanil both increase sedation. Use Caution/Monitor.

• alfuzosin

  aspirin decreases effects of alfuzosin by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.

• aliskiren

  aspirin will decrease the level or effect of aliskiren by Other (see comment). Use Caution/Monitor. In patients who are elderly, volume-depleted (including those on diuretic therapy), or with compromised renal function, coadministration of NSAIDs with drugs that affect RAAS may increase the risk of renal impairment (including acute renal failure) and cause loss of antihypertensive effect. Monitor renal function periodically.

• alprazolam

  alprazolam increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and alprazolam both increase sedation. Use Caution/Monitor.

• alteplase

  aspirin, alteplase. Either increases toxicity of the other by anticoagulation. Use Caution/Monitor. The need for simultaneous use of low-dose aspirin and anticoagulant or antiplatelet agents are common for patients with cardiovascular disease; monitor closely.

• amitriptyline

  amitriptyline increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• American ginseng

  aspirin and American ginseng both increase anticoagulation. Use Caution/Monitor.

• amifampridine

  chlorpheniramine increases toxicity of amifampridine by Other (see comment). Modify Therapy/Monitor Closely. Comment: Amifampridine can cause seizures. Coadministration with drugs that lower seizure threshold may increase this risk.

• amiloride

  amiloride and aspirin both increase serum potassium. Modify Therapy/Monitor Closely.

• amitriptyline

  chlorpheniramine and amitriptyline both increase sedation. Use Caution/Monitor.

• amobarbital

  amobarbital increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  amobarbital will decrease the level or effect of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  chlorpheniramine and amobarbital both increase sedation. Use Caution/Monitor.

• amoxapine

  amoxapine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and amoxapine both increase sedation. Use Caution/Monitor.

• amoxicillin

  amoxicillin, aspirin. Either increases levels of the other by plasma protein binding competition. Use Caution/Monitor.
  
  amoxicillin, aspirin. Either increases levels of the other by decreasing renal clearance. Use Caution/Monitor.

• arformoterol

  arformoterol and phenylephrine both decrease sedation. Use Caution/Monitor.
  
  arformoterol and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• ampicillin

  ampicillin, aspirin. Either increases levels of the other by plasma protein binding competition. Use Caution/Monitor.

• anagrelide

  aspirin, anagrelide. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. The need for simultaneous use of low-dose aspirin and anticoagulant or antiplatelet agents are common for patients with cardiovascular disease; increases risk of bleeding; monitor closely.
  
  anagrelide, aspirin. Either increases toxicity of the other by Mechanism: pharmacodynamic synergism. Use Caution/Monitor. The need for simultaneous use of low-dose aspirin and anticoagulant or antiplatelet agents are common for patients with cardiovascular disease; increases risk of bleeding; monitor closely.

• antithrombin alfa

  antithrombin alfa and aspirin both increase anticoagulation. Modify Therapy/Monitor Closely.
  
  aspirin, antithrombin alfa. Either increases toxicity of the other by anticoagulation. Use Caution/Monitor. The need for simultaneous use of low-dose aspirin and anticoagulant or antiplatelet agents are common for patients with cardiovascular disease; monitor closely.

• antithrombin III

  antithrombin III and aspirin both increase anticoagulation. Modify Therapy/Monitor Closely.
  
  aspirin, antithrombin III. Either increases toxicity of the other by anticoagulation. Use Caution/Monitor. The need for simultaneous use of low-dose aspirin and anticoagulant or antiplatelet agents are common for patients with cardiovascular disease; monitor closely.

• apixaban

  aspirin and apixaban both increase anticoagulation. Modify Therapy/Monitor Closely. Both drugs have the potential to cause bleeding. The need for simultaneous use of low-dose aspirin (<100 mg/day) with anticoagulants are common for patients with cardiovascular disease, but may result in increased bleeding; monitor closely. Promptly evaluate any signs or symptoms of blood loss if treated concomitantly with low-dose aspiriin. Avoid coadministration with chronic use of higher dose aspirin. In 1 trial (APPRAISE-2), therapy was terminated because of significantly increased bleeding when apixaban was administered with dual antiplatelet therapy (eg, aspirin plus clopidogrel) compared with single antiplatelet treatment

• apomorphine

  chlorpheniramine and apomorphine both increase sedation. Use Caution/Monitor.

• arformoterol

  chlorpheniramine increases and arformoterol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  aspirin increases and arformoterol decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• argatroban

  argatroban and aspirin both increase anticoagulation. Modify Therapy/Monitor Closely.
  
  aspirin, argatroban. Either increases toxicity of the other by anticoagulation. Use Caution/Monitor. The need for simultaneous use of low-dose aspirin and anticoagulant or antiplatelet agents are common for patients with cardiovascular disease; monitor closely.

• aripiprazole

  aripiprazole increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and aripiprazole both increase sedation. Use Caution/Monitor.

• armodafinil

  chlorpheniramine increases and armodafinil decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  armodafinil and phenylephrine both decrease sedation. Use Caution/Monitor.

• asenapine

  aspirin decreases effects of asenapine by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.

• atomoxetine

  atomoxetine, phenylephrine. Other (see comment). Use Caution/Monitor. Comment: Due to the potential for increases in blood pressure and heart rate, atomoxetine should be used cautiously with vasopressors such as phenylephrine.

• atenolol

  atenolol and aspirin both increase serum potassium. Use Caution/Monitor.
  
  aspirin decreases effects of atenolol by pharmacodynamic antagonism. Use Caution/Monitor. Long term (>1 wk) NSAID use. NSAIDs decrease prostaglandin synthesis.

• azelastine

  azelastine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  azelastine and chlorpheniramine both increase sedation. Use Caution/Monitor.

• azficel-T

  azficel-T, aspirin. Other (see comment). Use Caution/Monitor. Comment: Patients taking aspirin may experience increased bruising or bleeding at biopsy and/or injection sites. Concomitant use of aspirin is not recommended. .

• belladonna and opium

  belladonna and opium increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• azilsartan

  aspirin, azilsartan. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: May result in renal function deterioration, particularly in elderly or volume depleted individuals.
  
  aspirin decreases effects of azilsartan by pharmacodynamic antagonism. Modify Therapy/Monitor Closely. NSAIDs decrease synthesis of vasodilating renal prostaglandins, and thus affect fluid homeostasis and may diminish antihypertensive effect.

• baclofen

  chlorpheniramine and baclofen both increase sedation. Use Caution/Monitor.

• belladonna and opium

  chlorpheniramine and belladonna and opium both increase sedation. Use Caution/Monitor.

• belzutifan

  belzutifan will decrease the level or effect of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. If unable to avoid coadministration of belzutifan with sensitive CYP3A4 substrates, consider increasing the sensitive CYP3A4 substrate dose in accordance with its prescribing information.

• bemiparin

  bemiparin and aspirin both increase anticoagulation. Modify Therapy/Monitor Closely.

• benazepril

  benazepril, aspirin. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: May result in renal function deterioration, particularly with high dose aspirin, in elderly or volume depleted individuals.

• bendroflumethiazide

  aspirin increases and bendroflumethiazide decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• benperidol

  benperidol increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and benperidol both increase sedation. Use Caution/Monitor.

• benzphetamine

  chlorpheniramine increases and benzphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  benzphetamine and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  benzphetamine and phenylephrine both decrease sedation. Use Caution/Monitor.

• betaxolol

  betaxolol and aspirin both increase serum potassium. Use Caution/Monitor.
  
  aspirin decreases effects of betaxolol by pharmacodynamic antagonism. Use Caution/Monitor. Long term (>1 wk) NSAID use. NSAIDs decrease prostaglandin synthesis.

• bromocriptine

  bromocriptine, phenylephrine. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Hypertension, V tach.

• betrixaban

  aspirin, betrixaban. Either increases levels of the other by anticoagulation. Use Caution/Monitor.

• bimatoprost

  bimatoprost, aspirin. unspecified interaction mechanism. Use Caution/Monitor. There are conflicting reports from studies of either increased or decreased IOP when ophthalmic prostaglandins are coadministered with NSAIDs (either systemic or ophthalmic).

• bisoprolol

  bisoprolol and aspirin both increase serum potassium. Use Caution/Monitor.
  
  aspirin decreases effects of bisoprolol by pharmacodynamic antagonism. Use Caution/Monitor. Long term (>1 wk) NSAID use. NSAIDs decrease prostaglandin synthesis.

• bivalirudin

  bivalirudin and aspirin both increase anticoagulation. Modify Therapy/Monitor Closely.
  
  aspirin, bivalirudin. Either increases toxicity of the other by anticoagulation. Use Caution/Monitor. The need for simultaneous use of low-dose aspirin and anticoagulant or antiplatelet agents are common for patients with cardiovascular disease; monitor closely.

• brexanolone

  brexanolone, chlorpheniramine. Either increases toxicity of the other by sedation. Use Caution/Monitor.

• brinzolamide

  brinzolamide, aspirin. Either increases levels of the other by Other (see comment). Use Caution/Monitor. Comment: Carbonic anhydrase inhibitors (CAIs) and salicylates inhibit each other's renal tubular secretion, resulting in increased plasma levels. CAIs also shift salicylates from plasma to the CNS, leading to potential neurotoxicity.

• brompheniramine

  brompheniramine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  brompheniramine and chlorpheniramine both increase sedation. Use Caution/Monitor.

• bumetanide

  aspirin increases and bumetanide decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  aspirin decreases effects of bumetanide by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.

• buprenorphine buccal

  buprenorphine buccal increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• buprenorphine

  chlorpheniramine and buprenorphine both increase sedation. Use Caution/Monitor.

• buprenorphine buccal

  chlorpheniramine and buprenorphine buccal both increase sedation. Use Caution/Monitor.

• butabarbital

  butabarbital increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and butabarbital both increase sedation. Use Caution/Monitor.

• butalbital

  chlorpheniramine and butalbital both increase sedation. Use Caution/Monitor.
  
  butalbital increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• butorphanol

  chlorpheniramine and butorphanol both increase sedation. Use Caution/Monitor.
  
  butorphanol increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• caffeine

  chlorpheniramine increases and caffeine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  caffeine and phenylephrine both decrease sedation. Use Caution/Monitor.

• candesartan

  candesartan and aspirin both increase serum potassium. Use Caution/Monitor.
  
  aspirin decreases effects of candesartan by pharmacodynamic antagonism. Modify Therapy/Monitor Closely. NSAIDs decrease synthesis of vasodilating renal prostaglandins, and thus affect fluid homeostasis and may diminish antihypertensive effect.
  
  candesartan, aspirin. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: May result in renal function deterioration, particularly in elderly or volume depleted individuals.

• carbinoxamine

  carbinoxamine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• captopril

  captopril, aspirin. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: May result in renal function deterioration, particularly with high dose aspirin, elderly or volume depleted individuals.

• carbenoxolone

  aspirin increases and carbenoxolone decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• carbinoxamine

  carbinoxamine and chlorpheniramine both increase sedation. Use Caution/Monitor.

• carisoprodol

  chlorpheniramine and carisoprodol both increase sedation. Use Caution/Monitor.

• carvedilol

  carvedilol and aspirin both increase serum potassium. Use Caution/Monitor.
  
  aspirin decreases effects of carvedilol by pharmacodynamic antagonism. Use Caution/Monitor. Long term (>1 wk) NSAID use. NSAIDs decrease prostaglandin synthesis.

• celecoxib

  aspirin and celecoxib both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and celecoxib both increase serum potassium. Use Caution/Monitor.

• celiprolol

  celiprolol and aspirin both increase serum potassium. Use Caution/Monitor.
  
  aspirin decreases effects of celiprolol by pharmacodynamic antagonism. Use Caution/Monitor. Long term (>1 wk) NSAID use. NSAIDs decrease prostaglandin synthesis.

• cenobamate

  cenobamate will decrease the level or effect of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Increase dose of CYP3A4 substrate, as needed, when coadministered with cenobamate.
  
  cenobamate, chlorpheniramine. Either increases effects of the other by sedation. Use Caution/Monitor.

• chloral hydrate

  chlorpheniramine and chloral hydrate both increase sedation. Use Caution/Monitor.
  
  chloral hydrate increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• chlordiazepoxide

  chlorpheniramine and chlordiazepoxide both increase sedation. Use Caution/Monitor.
  
  chlordiazepoxide increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• chlorothiazide

  aspirin increases and chlorothiazide decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• chlorpheniramine

  chlorpheniramine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• chlorpromazine

  chlorpheniramine and chlorpromazine both increase sedation. Use Caution/Monitor.
  
  chlorpromazine, phenylephrine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.
  
  chlorpromazine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• chlorpropamide

  aspirin increases effects of chlorpropamide by unknown mechanism. Use Caution/Monitor. Risk of hypoglycemia.

• cinnarizine

  cinnarizine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• chlorthalidone

  aspirin increases and chlorthalidone decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• chlorzoxazone

  chlorpheniramine and chlorzoxazone both increase sedation. Use Caution/Monitor.

• choline magnesium trisalicylate

  aspirin and choline magnesium trisalicylate both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and choline magnesium trisalicylate both increase serum potassium. Use Caution/Monitor.

• cilostazol

  aspirin, cilostazol. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. The need for simultaneous use of low-dose aspirin and anticoagulant or antiplatelet agents are common for patients with cardiovascular disease; monitor closely.

• cinnamon

  aspirin and cinnamon both increase anticoagulation. Use Caution/Monitor.

• cinnarizine

  chlorpheniramine and cinnarizine both increase sedation. Use Caution/Monitor.

• ciprofloxacin

  aspirin decreases levels of ciprofloxacin by Other (see comment). Use Caution/Monitor. Comment: Buffered aspirin may decrease absorption of quinolones. Consider administering 2 hr before or 6 hr after, buffered aspirin administration.

• citalopram

  citalopram, aspirin. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of upper GI bleeding. If possible, avoid concurrent use.

• clemastine

  clemastine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and clemastine both increase sedation. Use Caution/Monitor.

• clobazam

  chlorpheniramine, clobazam. Other (see comment). Use Caution/Monitor. Comment: Concomitant administration can increase the potential for CNS effects (e.g., increased sedation or respiratory depression).

• clomipramine

  clomipramine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• clomipramine

  clomipramine, aspirin. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of upper GI bleeding. Clomipramine inhib. serotonin uptake by platelets.
  
  chlorpheniramine and clomipramine both increase sedation. Use Caution/Monitor.

• clonazepam

  clonazepam increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and clonazepam both increase sedation. Use Caution/Monitor.

• clopidogrel

  aspirin, clopidogrel. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. The need for simultaneous use of low-dose aspirin and anticoagulant or antiplatelet agents are common for patients with cardiovascular disease; monitor closely.

• clorazepate

  clorazepate increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• clorazepate

  chlorpheniramine and clorazepate both increase sedation. Use Caution/Monitor.

• clozapine

  clozapine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and clozapine both increase sedation. Use Caution/Monitor.

• codeine

  chlorpheniramine and codeine both increase sedation. Use Caution/Monitor.
  
  codeine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• collagenase clostridium histolyticum

  aspirin increases toxicity of collagenase clostridium histolyticum by anticoagulation. Use Caution/Monitor. Collagenase clostridium histolyticum has high incidence of ecchymosis/contusion at injection site; avoid concomitant anticoagulants (except for low-dose aspirin, ie, up to 150 mg/day).

• cyclizine

  cyclizine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• cordyceps

  aspirin and cordyceps both increase anticoagulation. Use Caution/Monitor.

• cortisone

  aspirin, cortisone. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of GI ulceration.

• crofelemer

  crofelemer increases levels of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Crofelemer has the potential to inhibit CYP3A4 at concentrations expected in the gut; unlikely to inhibit systemically because minimally absorbed.

• cyclizine

  chlorpheniramine and cyclizine both increase sedation. Use Caution/Monitor.

• cyclobenzaprine

  chlorpheniramine and cyclobenzaprine both increase sedation. Use Caution/Monitor.

• cyclopenthiazide

  aspirin increases and cyclopenthiazide decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• cyproheptadine

  cyproheptadine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and cyproheptadine both increase sedation. Use Caution/Monitor.

• dabigatran

  dabigatran and aspirin both increase anticoagulation. Modify Therapy/Monitor Closely. Both drugs have the potential to cause bleeding. The need for simultaneous use of low-dose aspirin (<100 mg/day) with anticoagulants are common for patients with cardiovascular disease, but may result in increased bleeding; monitor closely. Promptly evaluate any signs or symptoms of blood loss if treated concomitantly with low-dose aspirin. Avoid coadministration with chronic use of higher dose aspirin

• desipramine

  desipramine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• dabrafenib

  dabrafenib will decrease the level or effect of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely.

• dalteparin

  dalteparin and aspirin both increase anticoagulation. Modify Therapy/Monitor Closely.
  
  aspirin, dalteparin. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. The need for simultaneous use of low-dose aspirin and anticoagulant or antiplatelet agents are common for patients with cardiovascular disease; monitor closely.

• dantrolene

  chlorpheniramine and dantrolene both increase sedation. Use Caution/Monitor.

• daridorexant

  chlorpheniramine and daridorexant both increase sedation. Modify Therapy/Monitor Closely. Coadministration increases risk of CNS depression, which can lead to additive impairment of psychomotor performance and cause daytime impairment.

• deferasirox

  deferasirox, aspirin. Other (see comment). Use Caution/Monitor. Comment: Combination may increase GI bleeding, ulceration and irritation. Use with caution.

• defibrotide

  defibrotide increases effects of aspirin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. Defibrotide may enhance effects of platelet inhibitors.

• deflazacort

  aspirin, deflazacort. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of GI ulceration.

• desflurane

  desflurane and chlorpheniramine both increase sedation. Use Caution/Monitor.

• desipramine

  chlorpheniramine and desipramine both increase sedation. Use Caution/Monitor.

• desirudin

  aspirin, desirudin. Either increases levels of the other by pharmacodynamic synergism. Use Caution/Monitor. The need for simultaneous use of low-dose aspirin and anticoagulant or antiplatelet agents are common for patients with cardiovascular disease; monitor closely.

• deutetrabenazine

  chlorpheniramine and deutetrabenazine both increase sedation. Use Caution/Monitor.

• dexamethasone

  aspirin, dexamethasone. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of GI ulceration.

• dexchlorpheniramine

  dexchlorpheniramine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and dexchlorpheniramine both increase sedation. Use Caution/Monitor.

• dexfenfluramine

  chlorpheniramine increases and dexfenfluramine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  dexfenfluramine and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  dexfenfluramine and phenylephrine both decrease sedation. Use Caution/Monitor.

• dexmedetomidine

  dexmedetomidine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and dexmedetomidine both increase sedation. Use Caution/Monitor.

• dexmethylphenidate

  dexmethylphenidate and phenylephrine both decrease sedation. Use Caution/Monitor.
  
  chlorpheniramine increases and dexmethylphenidate decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  dexmethylphenidate and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• dextroamphetamine

  dextroamphetamine and phenylephrine both decrease sedation. Use Caution/Monitor.
  
  chlorpheniramine increases and dextroamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  dextroamphetamine and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• dextromoramide

  chlorpheniramine and dextromoramide both increase sedation. Use Caution/Monitor.
  
  dextromoramide increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• diamorphine

  chlorpheniramine and diamorphine both increase sedation. Use Caution/Monitor.
  
  diamorphine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• diazepam

  chlorpheniramine and diazepam both increase sedation. Use Caution/Monitor.

• diethylpropion

  diethylpropion and phenylephrine both decrease sedation. Use Caution/Monitor.
  
  diethylpropion and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• diazepam intranasal

  diazepam intranasal, chlorpheniramine. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Coadministration may potentiate the CNS-depressant effects of each drug.

• diclofenac

  aspirin and diclofenac both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and diclofenac both increase serum potassium. Use Caution/Monitor.

• dicloxacillin

  dicloxacillin, aspirin. Either increases levels of the other by plasma protein binding competition. Use Caution/Monitor.

• diethylpropion

  chlorpheniramine increases and diethylpropion decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• difelikefalin

  difelikefalin and chlorpheniramine both increase sedation. Use Caution/Monitor.

• difenoxin hcl

  difenoxin hcl increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and difenoxin hcl both increase sedation. Use Caution/Monitor.

• diflunisal

  aspirin and diflunisal both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and diflunisal both increase serum potassium. Use Caution/Monitor.

• dimenhydrinate

  dimenhydrinate increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• digoxin

  aspirin and digoxin both increase serum potassium. Use Caution/Monitor.

• dimenhydrinate

  chlorpheniramine and dimenhydrinate both increase sedation. Use Caution/Monitor.

• diphenhydramine

  diphenhydramine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and diphenhydramine both increase sedation. Use Caution/Monitor.

• diphenoxylate hcl

  chlorpheniramine and diphenoxylate hcl both increase sedation. Use Caution/Monitor.
  
  diphenoxylate hcl increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• dipipanone

  chlorpheniramine and dipipanone both increase sedation. Use Caution/Monitor.
  
  dipipanone increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• dipyridamole

  aspirin, dipyridamole. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. The need for simultaneous use of low-dose aspirin and anticoagulant or antiplatelet agents are common for patients with cardiovascular disease; monitor closely.

• dobutamine

  dobutamine and phenylephrine both decrease sedation. Use Caution/Monitor.
  
  dobutamine and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• dobutamine

  chlorpheniramine increases and dobutamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  aspirin increases and dobutamine decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• donepezil transdermal

  donepezil transdermal, chlorpheniramine. Either decreases effects of the other by pharmacodynamic antagonism. Use Caution/Monitor.

• dong quai

  aspirin and dong quai both increase anticoagulation. Use Caution/Monitor.

• dopamine

  dopamine and phenylephrine both decrease sedation. Use Caution/Monitor.
  
  chlorpheniramine increases and dopamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  dopamine and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• dopexamine

  aspirin increases and dopexamine decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine increases and dopexamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  dopexamine and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  dopexamine and phenylephrine both decrease sedation. Use Caution/Monitor.

• dosulepin

  chlorpheniramine and dosulepin both increase sedation. Use Caution/Monitor.

• doxepin

  doxepin increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• doxazosin

  aspirin decreases effects of doxazosin by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.

• doxepin

  chlorpheniramine and doxepin both increase sedation. Use Caution/Monitor.

• doxylamine

  chlorpheniramine and doxylamine both increase sedation. Use Caution/Monitor.

• droperidol

  droperidol increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and droperidol both increase sedation. Use Caution/Monitor.

• drospirenone

  drospirenone and aspirin both increase serum potassium. Modify Therapy/Monitor Closely.

• droxidopa

  phenylephrine and droxidopa both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor. May increase risk for supine hypertension

• duloxetine

  duloxetine, aspirin. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of upper GI bleeding. SSRIs inhib. serotonin uptake by platelets.

• edoxaban

  edoxaban, aspirin. Either increases toxicity of the other by anticoagulation. Modify Therapy/Monitor Closely. Both drugs have the potential to cause bleeding. The need for simultaneous use of low-dose aspirin (<100 mg/day) with anticoagulants are common for patients with cardiovascular disease, but may result in increased bleeding; monitor closely. Promptly evaluate any signs or symptoms of blood loss if treated concomitantly with low-dose aspirin. Avoid coadministration with chronic use of higher dose aspirin.

• efavirenz

  efavirenz will decrease the level or effect of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• elagolix

  elagolix will decrease the level or effect of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Elagolix is a weak-to-moderate CYP3A4 inducer. Monitor CYP3A substrates if coadministered. Consider increasing CYP3A substrate dose if needed.

• elvitegravir/cobicistat/emtricitabine/tenofovir DF

  elvitegravir/cobicistat/emtricitabine/tenofovir DF, aspirin. Either increases toxicity of the other by decreasing renal clearance. Modify Therapy/Monitor Closely. Toxicity may result from coadministration of emtricitabine and tenofovir with other drugs that are also primarily excreted by glomerular filtration and/or active tubular secretion including high-dose or multiple-dose NSAIDs; alternatives to NSAIDs should be considered.
  
  elvitegravir/cobicistat/emtricitabine/tenofovir DF increases levels of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. CYP3A4 substrates for which elevated plasma concentrations are associated with serious and/or life-threatening events.

• enalapril

  enalapril, aspirin. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: May result in renal function deterioration, particularly with high dose aspirin, in elderly or volume depleted individuals.

• ephedrine

  ephedrine, phenylephrine. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor.
  
  ephedrine and phenylephrine both decrease sedation. Use Caution/Monitor.
  
  chlorpheniramine increases and ephedrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  ephedrine and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• enoxaparin

  enoxaparin and aspirin both increase anticoagulation. Use Caution/Monitor. Additive effects are intended when both drugs are prescribed as indicated for unstable angina, non-Q-wave MI, and STEMI
  
  aspirin, enoxaparin. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. The need for simultaneous use of low-dose aspirin and anticoagulant or antiplatelet agents are common for patients with cardiovascular disease; monitor closely.

• epinephrine

  epinephrine and phenylephrine both decrease sedation. Use Caution/Monitor.
  
  epinephrine and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• ephedrine

  aspirin increases and ephedrine decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• epinephrine

  aspirin increases and epinephrine decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine increases and epinephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• epinephrine inhaled

  phenylephrine, epinephrine inhaled. Either increases effects of the other by sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• epinephrine racemic

  epinephrine racemic and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  chlorpheniramine increases and epinephrine racemic decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  aspirin increases and epinephrine racemic decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  epinephrine racemic and phenylephrine both decrease sedation. Use Caution/Monitor.

• epoprostenol

  aspirin and epoprostenol both increase anticoagulation. Use Caution/Monitor.

• estazolam

  estazolam increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• esketamine intranasal

  esketamine intranasal, chlorpheniramine. Either increases toxicity of the other by sedation. Modify Therapy/Monitor Closely.

• eprosartan

  eprosartan and aspirin both increase serum potassium. Use Caution/Monitor.
  
  aspirin decreases effects of eprosartan by pharmacodynamic antagonism. Modify Therapy/Monitor Closely. NSAIDs decrease synthesis of vasodilating renal prostaglandins, and thus affect fluid homeostasis and may diminish antihypertensive effect.
  
  eprosartan, aspirin. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: May result in renal function deterioration, particularly in elderly or volume depleted individuals.

• eptifibatide

  aspirin, eptifibatide. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. The need for simultaneous use of low-dose aspirin and anticoagulant or antiplatelet agents are common for patients with cardiovascular disease; monitor closely.

• escitalopram

  escitalopram, aspirin. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of upper GI bleeding. SSRIs inhib. serotonin uptake by platelets.

• esmolol

  esmolol and aspirin both increase serum potassium. Use Caution/Monitor.
  
  aspirin decreases effects of esmolol by pharmacodynamic antagonism. Use Caution/Monitor. Long term (>1 wk) NSAID use. NSAIDs decrease prostaglandin synthesis.

• estazolam

  chlorpheniramine and estazolam both increase sedation. Use Caution/Monitor.

• ethacrynic acid

  aspirin increases and ethacrynic acid decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• ethanol

  ethanol increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and ethanol both increase sedation. Use Caution/Monitor.

• etodolac

  aspirin and etodolac both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and etodolac both increase serum potassium. Use Caution/Monitor.

• fenfluramine

  fenfluramine and phenylephrine both decrease sedation. Use Caution/Monitor.
  
  fenfluramine and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• etomidate

  etomidate and chlorpheniramine both increase sedation. Use Caution/Monitor.

• fedratinib

  fedratinib will increase the level or effect of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Adjust dose of drugs that are CYP3A4 substrates as necessary.

• fenbufen

  aspirin and fenbufen both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and fenbufen both increase serum potassium. Use Caution/Monitor.

• fenfluramine

  chlorpheniramine increases and fenfluramine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• fennel

  aspirin and fennel both increase anticoagulation. Use Caution/Monitor.

• fenoprofen

  aspirin and fenoprofen both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and fenoprofen both increase serum potassium. Use Caution/Monitor.

• fentanyl

  fentanyl, chlorpheniramine. Either increases toxicity of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Coadministration of fentanyl with anticholinergics may increase risk for urinary retention and/or severe constipation, which may lead to paralytic ileus.

• fentanyl intranasal

  fentanyl intranasal, chlorpheniramine. Either increases toxicity of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Coadministration of fentanyl with anticholinergics may increase risk for urinary retention and/or severe constipation, which may lead to paralytic ileus.

• fentanyl transdermal

  fentanyl transdermal, chlorpheniramine. Either increases toxicity of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Coadministration of fentanyl with anticholinergics may increase risk for urinary retention and/or severe constipation, which may lead to paralytic ileus.

• fentanyl transmucosal

  fentanyl transmucosal, chlorpheniramine. Either increases toxicity of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Coadministration of fentanyl with anticholinergics may increase risk for urinary retention and/or severe constipation, which may lead to paralytic ileus.

• feverfew

  aspirin and feverfew both increase anticoagulation. Use Caution/Monitor.

• fish oil

  fish oil, aspirin. Other (see comment). Use Caution/Monitor. Comment: Patients taking fish oil and an anticoagulant or other drug affecting coagulation should be monitored periodically due to potential increased risk of bleeding. .

• fish oil triglycerides

  fish oil triglycerides will increase the level or effect of aspirin by anticoagulation. Use Caution/Monitor. Prolonged bleeding reported in patients taking antiplatelet agents or anticoagulants and oral omega-3 fatty acids. Periodically monitor bleeding time in patients receiving fish oil triglycerides and concomitant antiplatelet agents or anticoagulants.

• flibanserin

  chlorpheniramine and flibanserin both increase sedation. Modify Therapy/Monitor Closely. Risk for sedation increased if flibanserin is coadministration with other CNS depressants.

• fludrocortisone

  aspirin, fludrocortisone. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of GI ulceration.

• fluoxetine

  fluoxetine, aspirin. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of upper GI bleeding. SSRIs inhib. serotonin uptake by platelets.

• fluphenazine

  fluphenazine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and fluphenazine both increase sedation. Use Caution/Monitor.
  
  fluphenazine, phenylephrine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.

• flurazepam

  chlorpheniramine and flurazepam both increase sedation. Use Caution/Monitor.
  
  flurazepam increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• flurbiprofen

  aspirin and flurbiprofen both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and flurbiprofen both increase serum potassium. Use Caution/Monitor.

• formoterol

  formoterol and phenylephrine both decrease sedation. Use Caution/Monitor.
  
  formoterol and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• fluvoxamine

  fluvoxamine, aspirin. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of upper GI bleeding SSRIs inhib. serotonin uptake by platelets.

• fondaparinux

  fondaparinux and aspirin both increase anticoagulation. Modify Therapy/Monitor Closely.

• formoterol

  chlorpheniramine increases and formoterol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  aspirin increases and formoterol decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• forskolin

  aspirin and forskolin both increase anticoagulation. Use Caution/Monitor.

• fosphenytoin

  fosphenytoin will decrease the level or effect of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• fosinopril

  fosinopril, aspirin. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: May result in renal function deterioration, particularly with high dose aspirin, in elderly or volume depleted individuals.

• furosemide

  aspirin increases and furosemide decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• gabapentin

  gabapentin, chlorpheniramine. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Coadministration of CNS depressants can result in serious, life-threatening, and fatal respiratory depression. Use lowest dose possible and monitor for respiratory depression and sedation.

• gabapentin enacarbil

  gabapentin enacarbil, chlorpheniramine. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Coadministration of CNS depressants can result in serious, life-threatening, and fatal respiratory depression. Use lowest dose possible and monitor for respiratory depression and sedation.

• ganaxolone

  chlorpheniramine and ganaxolone both increase sedation. Use Caution/Monitor.

• garlic

  aspirin and garlic both increase anticoagulation. Use Caution/Monitor.

• gentamicin

  aspirin increases and gentamicin decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• ginger

  aspirin and ginger both increase anticoagulation. Use Caution/Monitor.

• ginkgo biloba

  aspirin and ginkgo biloba both increase anticoagulation. Use Caution/Monitor.

• glimepiride

  aspirin increases effects of glimepiride by unknown mechanism. Use Caution/Monitor. Risk of hypoglycemia.

• glipizide

  aspirin increases effects of glipizide by unknown mechanism. Use Caution/Monitor. Risk of hypoglycemia.

• glyburide

  aspirin increases effects of glyburide by unknown mechanism. Use Caution/Monitor. Risk of hypoglycemia.

• glycopyrronium tosylate topical

  glycopyrronium tosylate topical, chlorpheniramine. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Coadministration of glycopyrronium tosylate topical with other anticholinergic medications may result in additive anticholinergic adverse effects.

• gotu kola

  gotu kola increases effects of chlorpheniramine by pharmacodynamic synergism. Use Caution/Monitor. May enhance CNS depression.

• green tea

  green tea increases effects of aspirin by pharmacodynamic synergism. Use Caution/Monitor. (Theoretical, due to caffeine content). Combination may increase risk of bleeding.

• griseofulvin

  griseofulvin decreases levels of aspirin by unknown mechanism. Use Caution/Monitor.

• haloperidol

  haloperidol increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and haloperidol both increase sedation. Use Caution/Monitor.

• hawthorn

  hawthorn increases effects of chlorpheniramine by pharmacodynamic synergism. Use Caution/Monitor. May enhance CNS depression.

• hydralazine

  hydralazine, phenylephrine. Mechanism: pharmacodynamic antagonism. Use Caution/Monitor. Sympathomimetics can antagonize the activity of some antihypertensive agents.

• heparin

  heparin and aspirin both increase anticoagulation. Modify Therapy/Monitor Closely.
  
  aspirin, heparin. Either increases toxicity of the other by anticoagulation. Use Caution/Monitor. The need for simultaneous use of low-dose aspirin and anticoagulant or antiplatelet agents are common for patients with cardiovascular disease; monitor closely.

• hops

  hops increases effects of chlorpheniramine by pharmacodynamic synergism. Use Caution/Monitor. May enhance CNS depression.

• horse chestnut seed

  aspirin and horse chestnut seed both increase anticoagulation. Use Caution/Monitor.

• hyaluronidase

  chlorpheniramine decreases effects of hyaluronidase by Other (see comment). Use Caution/Monitor. Comment: Antihistamines, when given in large systemic doses, may render tissues partially resistant to the action of hyaluronidase. Patients may require larger amounts of hyaluronidase for equivalent dispersing effect.
  
  aspirin decreases effects of hyaluronidase by Other (see comment). Use Caution/Monitor. Comment: Salicylates, when given in large systemic doses, may render tissues partially resistant to the action of hyaluronidase. Patients may require larger amounts of hyaluronidase for equivalent dispersing effect.

• hydralazine

  aspirin decreases effects of hydralazine by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.

• hydromorphone

  chlorpheniramine and hydromorphone both increase sedation. Use Caution/Monitor.
  
  hydromorphone increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• hydrochlorothiazide

  aspirin increases and hydrochlorothiazide decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• hydroxyzine

  hydroxyzine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• hydrocortisone

  aspirin, hydrocortisone. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of GI ulceration.

• hydroxyzine

  chlorpheniramine and hydroxyzine both increase sedation. Use Caution/Monitor.

• ibrutinib

  ibrutinib will increase the level or effect of aspirin by anticoagulation. Use Caution/Monitor. Ibrutinib may increase the risk of hemorrhage in patients receiving antiplatelet or anticoagulant therapies and monitor for signs of bleeding.

• ibuprofen

  aspirin and ibuprofen both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and ibuprofen both increase serum potassium. Use Caution/Monitor.

• ibuprofen IV

  aspirin will increase the level or effect of ibuprofen IV by acidic (anionic) drug competition for renal tubular clearance. Modify Therapy/Monitor Closely.
  
  aspirin and ibuprofen IV both increase anticoagulation. Modify Therapy/Monitor Closely.
  
  aspirin and ibuprofen IV both increase serum potassium. Use Caution/Monitor.

• icosapent

  icosapent, aspirin. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Icosapent may prolong bleeding time; monitor periodically if coadministered with other drugs that affect bleeding.

• iloperidone

  iloperidone increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and iloperidone both increase sedation. Use Caution/Monitor.
  
  iloperidone increases levels of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Iloperidone is a time-dependent CYP3A inhibitor and may lead to increased plasma levels of drugs predominantly eliminated by CYP3A4.

• imatinib

  imatinib, aspirin. Either increases toxicity of the other by Other (see comment). Modify Therapy/Monitor Closely. Comment: Imatinib may cause thrombocytopenia; bleeding risk increased when imatinib is coadministered with anticoagulants, NSAIDs, platelet inhibitors, and thrombolytic agents.

• imipramine

  imipramine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• imipramine

  chlorpheniramine and imipramine both increase sedation. Use Caution/Monitor.

• indacaterol, inhaled

  phenylephrine increases effects of indacaterol, inhaled by Other (see comment). Use Caution/Monitor. Comment: If additional adrenergic drugs are to be administered by any route, they should be used with caution because the sympathetic effects of indacaterol may be potentiated.

• indapamide

  aspirin increases and indapamide decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• indomethacin

  aspirin and indomethacin both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and indomethacin both increase serum potassium. Use Caution/Monitor.

• insulin aspart

  aspirin increases effects of insulin aspart by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Coadministration of insulin with high doses of salicylates (3 g/day or more) may increase risk for hypoglycemia. Insulin dose adjustment and increased frequency of glucose monitoring may be required.

• insulin aspart protamine/insulin aspart

  aspirin increases effects of insulin aspart protamine/insulin aspart by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Coadministration of insulin with high doses of salicylates (3 g/day or more) may increase risk for hypoglycemia. Insulin dose adjustment and increased frequency of glucose monitoring may be required.

• insulin degludec

  aspirin increases effects of insulin degludec by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Coadministration of insulin with high doses of salicylates (3 g/day or more) may increase risk for hypoglycemia. Insulin dose adjustment and increased frequency of glucose monitoring may be required.
  
  phenylephrine decreases effects of insulin degludec by pharmacodynamic antagonism. Modify Therapy/Monitor Closely. Sympathomimetics increase blood glucose by stimulating alpha and beta receptors; this action results in increased hepatic glucose production, glycogenolysis, and decreased insulin secretion.

• insulin degludec/insulin aspart

  phenylephrine decreases effects of insulin degludec/insulin aspart by pharmacodynamic antagonism. Modify Therapy/Monitor Closely. Sympathomimetics increase blood glucose by stimulating alpha and beta receptors; this action results in increased hepatic glucose production, glycogenolysis, and decreased insulin secretion.
  
  aspirin, insulin degludec/insulin aspart. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Both drugs decrease blood glucose.

• insulin detemir

  aspirin increases effects of insulin detemir by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Coadministration of insulin with high doses of salicylates (3 g/day or more) may increase risk for hypoglycemia. Insulin dose adjustment and increased frequency of glucose monitoring may be required.

• insulin inhaled

  phenylephrine decreases effects of insulin inhaled by pharmacodynamic antagonism. Modify Therapy/Monitor Closely. Sympathomimetics increase blood glucose by stimulating alpha and beta receptors; this action results in increased hepatic glucose production, glycogenolysis, and decreased insulin secretion.

• insulin glargine

  aspirin increases effects of insulin glargine by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Coadministration of insulin with high doses of salicylates (3 g/day or more) may increase risk for hypoglycemia. Insulin dose adjustment and increased frequency of glucose monitoring may be required.

• insulin glulisine

  aspirin increases effects of insulin glulisine by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Coadministration of insulin with high doses of salicylates (3 g/day or more) may increase risk for hypoglycemia. Insulin dose adjustment and increased frequency of glucose monitoring may be required.

• insulin inhaled

  aspirin increases effects of insulin inhaled by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Coadministration of insulin with high doses of salicylates (3 g/day or more) may increase risk for hypoglycemia. Insulin dose adjustment and increased frequency of glucose monitoring may be required.

• insulin isophane human/insulin regular human

  aspirin increases effects of insulin isophane human/insulin regular human by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Coadministration of insulin with high doses of salicylates (3 g/day or more) may increase risk for hypoglycemia. Insulin dose adjustment and increased frequency of glucose monitoring may be required.

• insulin lispro

  aspirin increases effects of insulin lispro by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Coadministration of insulin with high doses of salicylates (3 g/day or more) may increase risk for hypoglycemia. Insulin dose adjustment and increased frequency of glucose monitoring may be required.

• insulin lispro protamine/insulin lispro

  aspirin increases effects of insulin lispro protamine/insulin lispro by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Coadministration of insulin with high doses of salicylates (3 g/day or more) may increase risk for hypoglycemia. Insulin dose adjustment and increased frequency of glucose monitoring may be required.

• insulin NPH

  aspirin increases effects of insulin NPH by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Coadministration of insulin with high doses of salicylates (3 g/day or more) may increase risk for hypoglycemia. Insulin dose adjustment and increased frequency of glucose monitoring may be required.

• insulin regular human

  aspirin increases effects of insulin regular human by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Coadministration of insulin with high doses of salicylates (3 g/day or more) may increase risk for hypoglycemia. Insulin dose adjustment and increased frequency of glucose monitoring may be required.

• irbesartan

  irbesartan and aspirin both increase serum potassium. Use Caution/Monitor.
  
  aspirin decreases effects of irbesartan by pharmacodynamic antagonism. Modify Therapy/Monitor Closely. NSAIDs decrease synthesis of vasodilating renal prostaglandins, and thus affect fluid homeostasis and may diminish antihypertensive effect.
  
  irbesartan, aspirin. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: May result in renal function deterioration, particularly in elderly or volume depleted individuals.

• isoproterenol

  isoproterenol and phenylephrine both decrease sedation. Use Caution/Monitor.
  
  chlorpheniramine increases and isoproterenol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  aspirin increases and isoproterenol decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  isoproterenol and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• istradefylline

  istradefylline will increase the level or effect of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Istradefylline 40 mg/day increased peak levels and AUC of CYP3A4 substrates in clinical trials. This effect was not observed with istradefylline 20 mg/day. Consider dose reduction of sensitive CYP3A4 substrates.

• ketotifen, ophthalmic

  ketotifen, ophthalmic increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• ketoprofen

  aspirin and ketoprofen both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and ketoprofen both increase serum potassium. Use Caution/Monitor.

• kava

  kava increases effects of chlorpheniramine by pharmacodynamic synergism. Use Caution/Monitor. May enhance CNS depression.

• ketamine

  ketamine and chlorpheniramine both increase sedation. Use Caution/Monitor.

• ketorolac

  aspirin and ketorolac both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and ketorolac both increase serum potassium. Use Caution/Monitor.

• ketorolac intranasal

  aspirin and ketorolac intranasal both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and ketorolac intranasal both increase serum potassium. Use Caution/Monitor.

• ketotifen, ophthalmic

  chlorpheniramine and ketotifen, ophthalmic both increase sedation. Use Caution/Monitor.

• labetalol

  labetalol and aspirin both increase serum potassium. Use Caution/Monitor.
  
  aspirin decreases effects of labetalol by pharmacodynamic antagonism. Use Caution/Monitor. Long term (>1 wk) NSAID use. NSAIDs decrease prostaglandin synthesis.

• lasmiditan

  lasmiditan, chlorpheniramine. Either increases effects of the other by sedation. Use Caution/Monitor. Coadministration of lasmiditan and other CNS depressant drugs, including alcohol have not been evaluated in clinical studies. Lasmiditan may cause sedation, as well as other cognitive and/or neuropsychiatric adverse reactions.

• latanoprost

  latanoprost, aspirin. unspecified interaction mechanism. Use Caution/Monitor. There are conflicting reports from studies of either increased or decreased IOP when ophthalmic prostaglandins are coadministered with NSAIDs (either systemic or ophthalmic).

• latanoprostene bunod ophthalmic

  latanoprostene bunod ophthalmic, aspirin. unspecified interaction mechanism. Use Caution/Monitor. There are conflicting reports from studies of either increased or decreased IOP when ophthalmic prostaglandins are coadministered with NSAIDs (either systemic or ophthalmic).

• lemborexant

  lemborexant, chlorpheniramine. Either increases effects of the other by sedation. Modify Therapy/Monitor Closely. Dosage adjustment may be necessary if lemborexant is coadministered with other CNS depressants because of potentially additive effects.

• letermovir

  letermovir increases levels of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• levalbuterol

  aspirin increases and levalbuterol decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  levalbuterol and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  chlorpheniramine increases and levalbuterol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  levalbuterol and phenylephrine both decrease sedation. Use Caution/Monitor.

• levomilnacipran

  levomilnacipran, aspirin. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. SNRIs may further impair platelet activity in patients taking antiplatelet or anticoagulant drugs.

• levorphanol

  levorphanol increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• levorphanol

  chlorpheniramine and levorphanol both increase sedation. Use Caution/Monitor.

• lisdexamfetamine

  lisdexamfetamine and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  lisdexamfetamine and phenylephrine both decrease sedation. Use Caution/Monitor.
  
  chlorpheniramine increases and lisdexamfetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• lisinopril

  lisinopril, aspirin. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: May result in renal function deterioration, particularly with high dose aspirin, in elderly or volume depleted individuals.

• lofepramine

  lofepramine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• lithium

  aspirin increases levels of lithium by decreasing renal clearance. Use Caution/Monitor.

• lofepramine

  chlorpheniramine and lofepramine both increase sedation. Use Caution/Monitor.

• lofexidine

  lofexidine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and lofexidine both increase sedation. Use Caution/Monitor.

• loprazolam

  loprazolam increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and loprazolam both increase sedation. Use Caution/Monitor.

• lorazepam

  chlorpheniramine and lorazepam both increase sedation. Use Caution/Monitor.
  
  lorazepam increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• lormetazepam

  chlorpheniramine and lormetazepam both increase sedation. Use Caution/Monitor.
  
  lormetazepam increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• lornoxicam

  aspirin and lornoxicam both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and lornoxicam both increase serum potassium. Use Caution/Monitor.

• loxapine

  loxapine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• losartan

  losartan and aspirin both increase serum potassium. Use Caution/Monitor.
  
  aspirin decreases effects of losartan by pharmacodynamic antagonism. Modify Therapy/Monitor Closely. NSAIDs decrease synthesis of vasodilating renal prostaglandins, and thus affect fluid homeostasis and may diminish antihypertensive effect.
  
  losartan, aspirin. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: May result in renal function deterioration, particularly in elderly or volume depleted individuals.

• loxapine

  chlorpheniramine and loxapine both increase sedation. Use Caution/Monitor.

• loxapine inhaled

  loxapine inhaled increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and loxapine inhaled both increase sedation. Use Caution/Monitor.

• lurasidone

  lurasidone, chlorpheniramine. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: Potential for increased CNS depressant effects when used concurrently; monitor for increased adverse effects and toxicity.

• maprotiline

  maprotiline increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• maprotiline

  chlorpheniramine and maprotiline both increase sedation. Use Caution/Monitor.

• marijuana

  chlorpheniramine and marijuana both increase sedation. Use Caution/Monitor.
  
  marijuana increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• meclofenamate

  aspirin and meclofenamate both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and meclofenamate both increase serum potassium. Use Caution/Monitor.

• melatonin

  melatonin increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• mefenamic acid

  aspirin and mefenamic acid both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and mefenamic acid both increase serum potassium. Use Caution/Monitor.

• melatonin

  melatonin increases effects of aspirin by anticoagulation. Use Caution/Monitor. Melatonin may decrease prothrombin time.
  
  chlorpheniramine and melatonin both increase sedation. Use Caution/Monitor.

• meloxicam

  aspirin and meloxicam both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and meloxicam both increase serum potassium. Use Caution/Monitor.

• meperidine

  meperidine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and meperidine both increase sedation. Use Caution/Monitor.

• meprobamate

  meprobamate increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and meprobamate both increase sedation. Use Caution/Monitor.

• mesalamine

  mesalamine, aspirin. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Additive nephrotoxicity.

• metaproterenol

  metaproterenol and phenylephrine both decrease sedation. Use Caution/Monitor.
  
  metaproterenol and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• metaproterenol

  aspirin increases and metaproterenol decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine increases and metaproterenol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• metaxalone

  chlorpheniramine and metaxalone both increase sedation. Use Caution/Monitor.

• methadone

  methadone increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• methamphetamine

  methamphetamine and phenylephrine both decrease sedation. Use Caution/Monitor.
  
  methamphetamine and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• methazolamide

  methazolamide, aspirin. Either increases levels of the other by Other (see comment). Use Caution/Monitor. Comment: Carbonic anhydrase inhibitors (CAIs) and salicylates inhibit each other's renal tubular secretion, resulting in increased plasma levels. CAIs also shift salicylates from plasma to the CNS, leading to potential neurotoxicity.

• methadone

  chlorpheniramine and methadone both increase sedation. Use Caution/Monitor.

• methamphetamine

  chlorpheniramine increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• methocarbamol

  chlorpheniramine and methocarbamol both increase sedation. Use Caution/Monitor.

• methyclothiazide

  aspirin increases and methyclothiazide decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor. .

• methyldopa

  methyldopa increases effects of phenylephrine by unknown mechanism. Use Caution/Monitor.

• methylenedioxymethamphetamine

  chlorpheniramine increases and methylenedioxymethamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  methylenedioxymethamphetamine and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  methylenedioxymethamphetamine and phenylephrine both decrease sedation. Use Caution/Monitor.

• methylprednisolone

  aspirin, methylprednisolone. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of GI ulceration.

• midazolam

  midazolam increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• metolazone

  aspirin increases and metolazone decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• metoprolol

  metoprolol and aspirin both increase serum potassium. Use Caution/Monitor.
  
  aspirin decreases effects of metoprolol by pharmacodynamic antagonism. Use Caution/Monitor. Long term (>1 wk) NSAID use. NSAIDs decrease prostaglandin synthesis.

• midazolam

  chlorpheniramine and midazolam both increase sedation. Use Caution/Monitor.

• midazolam intranasal

  midazolam intranasal, chlorpheniramine. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Concomitant use of barbiturates, alcohol, or other CNS depressants may increase the risk of hypoventilation, airway obstruction, desaturation, or apnea and may contribute to profound and/or prolonged drug effect.

• midodrine

  midodrine and phenylephrine both decrease sedation. Use Caution/Monitor.
  
  chlorpheniramine increases and midodrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  midodrine and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• milnacipran

  milnacipran, aspirin. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of upper GI bleeding. SSRIs inhib. serotonin uptake by platelets.

• mirtazapine

  mirtazapine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• mirtazapine

  chlorpheniramine and mirtazapine both increase sedation. Use Caution/Monitor.

• mistletoe

  aspirin increases and mistletoe decreases anticoagulation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• mitotane

  mitotane decreases levels of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Mitotane is a strong inducer of cytochrome P-4503A4; monitor when coadministered with CYP3A4 substrates for possible dosage adjustments.

• modafinil

  modafinil and phenylephrine both decrease sedation. Use Caution/Monitor.
  
  chlorpheniramine increases and modafinil decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• moexipril

  moexipril, aspirin. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: May result in renal function deterioration, particularly with high dose aspirin, in elderly or volume depleted individuals.

• morphine

  morphine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• morphine

  chlorpheniramine and morphine both increase sedation. Use Caution/Monitor.

• motherwort

  chlorpheniramine and motherwort both increase sedation. Use Caution/Monitor.
  
  motherwort increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• moxisylyte

  aspirin decreases effects of moxisylyte by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.

• moxonidine

  moxonidine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• moxonidine

  chlorpheniramine and moxonidine both increase sedation. Use Caution/Monitor.

• mycophenolate

  aspirin will increase the level or effect of mycophenolate by acidic (anionic) drug competition for renal tubular clearance. Use Caution/Monitor.

• nabilone

  nabilone increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and nabilone both increase sedation. Use Caution/Monitor.

• nabumetone

  aspirin and nabumetone both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and nabumetone both increase serum potassium. Use Caution/Monitor.

• nadolol

  nadolol increases effects of phenylephrine by pharmacodynamic synergism. Use Caution/Monitor. Risk of acute hypertensive episode (rare).

• nadolol

  nadolol and aspirin both increase serum potassium. Use Caution/Monitor.
  
  aspirin decreases effects of nadolol by pharmacodynamic antagonism. Use Caution/Monitor. Long term (>1 wk) NSAID use. NSAIDs decrease prostaglandin synthesis.

• nafcillin

  nafcillin, aspirin. Either increases levels of the other by plasma protein binding competition. Use Caution/Monitor.
  
  nafcillin, aspirin. Either increases levels of the other by decreasing renal clearance. Use Caution/Monitor.

• nalbuphine

  nalbuphine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and nalbuphine both increase sedation. Use Caution/Monitor.

• naproxen

  aspirin and naproxen both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and naproxen both increase serum potassium. Use Caution/Monitor.

• norepinephrine

  norepinephrine and phenylephrine both decrease sedation. Use Caution/Monitor.
  
  norepinephrine and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• nebivolol

  nebivolol and aspirin both increase serum potassium. Use Caution/Monitor.
  
  aspirin decreases effects of nebivolol by pharmacodynamic antagonism. Use Caution/Monitor. Long term (>1 wk) NSAID use. NSAIDs decrease prostaglandin synthesis.

• nefazodone

  nefazodone, aspirin. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of upper GI bleeding. SSRIs inhib. serotonin uptake by platelets.

• nettle

  aspirin increases and nettle decreases anticoagulation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• nitazoxanide

  nitazoxanide, aspirin. Either increases levels of the other by Mechanism: plasma protein binding competition. Use Caution/Monitor.

• nitroglycerin rectal

  aspirin will increase the level or effect of nitroglycerin rectal by Other (see comment). Use Caution/Monitor. The pharmacological effects of nitroglycerin may be enhanced by concomitant administration of aspirin.

• nitroglycerin sublingual

  aspirin increases effects of nitroglycerin sublingual by additive vasodilation. Use Caution/Monitor. Vasodilatory and hemodynamic effects of NTG may be enhanced by coadministration with aspirin (additive effect desirable for emergent treatment).

• norepinephrine

  aspirin increases and norepinephrine decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine increases and norepinephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• nortriptyline

  nortriptyline increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and nortriptyline both increase sedation. Use Caution/Monitor.

• olanzapine

  olanzapine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• olanzapine

  chlorpheniramine and olanzapine both increase sedation. Use Caution/Monitor.

• olmesartan

  olmesartan and aspirin both increase serum potassium. Use Caution/Monitor.
  
  aspirin decreases effects of olmesartan by pharmacodynamic antagonism. Modify Therapy/Monitor Closely. NSAIDs decrease synthesis of vasodilating renal prostaglandins, and thus affect fluid homeostasis and may diminish antihypertensive effect.
  
  olmesartan, aspirin. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: May result in renal function deterioration, particularly in elderly or volume depleted individuals.

• olodaterol inhaled

  phenylephrine and olodaterol inhaled both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor. Caution with coadministration of adrenergic drugs by any route because of additive sympathetic effects

• omega 3 carboxylic acids

  omega 3 carboxylic acids, aspirin. Other (see comment). Use Caution/Monitor. Comment: Patients taking omega-3 acids and an anticoagulant or other drug affecting coagulation should be monitored periodically due to potential increased risk of bleeding.

• omega 3 fatty acids

  omega 3 fatty acids, aspirin. Other (see comment). Use Caution/Monitor. Comment: Patients taking omega-3-fatty acids and an anticoagulant or other drug affecting coagulation should be monitored periodically due to potential increased risk of bleeding. .

• opium tincture

  chlorpheniramine and opium tincture both increase sedation. Use Caution/Monitor.
  
  opium tincture increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• orphenadrine

  chlorpheniramine and orphenadrine both increase sedation. Use Caution/Monitor.

• oxazepam

  oxazepam increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• ospemifene

  aspirin, ospemifene. Either increases levels of the other by plasma protein binding competition. Modify Therapy/Monitor Closely.

• oxacillin

  oxacillin, aspirin. Either increases levels of the other by plasma protein binding competition. Use Caution/Monitor.
  
  oxacillin, aspirin. Either increases levels of the other by decreasing renal clearance. Use Caution/Monitor.

• oxaprozin

  aspirin and oxaprozin both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and oxaprozin both increase serum potassium. Use Caution/Monitor.

• oxazepam

  chlorpheniramine and oxazepam both increase sedation. Use Caution/Monitor.

• oxycodone

  oxycodone increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and oxycodone both increase sedation. Use Caution/Monitor.

• oxymetazoline topical

  oxymetazoline topical and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• oxymorphone

  chlorpheniramine and oxymorphone both increase sedation. Use Caution/Monitor.

• oxymorphone

  oxymorphone increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• oxytocin

  oxytocin increases effects of phenylephrine by pharmacodynamic synergism. Use Caution/Monitor.

• paliperidone

  chlorpheniramine and paliperidone both increase sedation. Use Caution/Monitor.
  
  paliperidone increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• panax ginseng

  aspirin and panax ginseng both increase anticoagulation. Use Caution/Monitor.

• papaveretum

  papaveretum increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• papaveretum

  chlorpheniramine and papaveretum both increase sedation. Use Caution/Monitor.

• papaverine

  chlorpheniramine and papaverine both increase sedation. Use Caution/Monitor.

• parecoxib

  aspirin and parecoxib both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and parecoxib both increase serum potassium. Use Caution/Monitor.

• paroxetine

  paroxetine, aspirin. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of upper GI bleeding. SSRIs inhib. serotonin uptake by platelets.

• passion flower

  passion flower increases effects of chlorpheniramine by pharmacodynamic synergism. Use Caution/Monitor. May enhance CNS depression.

• pau d'arco

  aspirin and pau d'arco both increase anticoagulation. Use Caution/Monitor.

• pegaspargase

  pegaspargase increases effects of aspirin by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of bleeding events.

• penbutolol

  penbutolol and aspirin both increase serum potassium. Use Caution/Monitor.
  
  aspirin decreases effects of penbutolol by pharmacodynamic antagonism. Use Caution/Monitor. Long term (>1 wk) NSAID use. NSAIDs decrease prostaglandin synthesis.

• penicillin G aqueous

  penicillin G aqueous, aspirin. Either increases levels of the other by plasma protein binding competition. Use Caution/Monitor.
  
  penicillin G aqueous, aspirin. Either increases levels of the other by decreasing renal clearance. Use Caution/Monitor.

• pentazocine

  chlorpheniramine and pentazocine both increase sedation. Use Caution/Monitor.
  
  pentazocine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• pentobarbital

  chlorpheniramine and pentobarbital both increase sedation. Use Caution/Monitor.
  
  pentobarbital increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• perindopril

  perindopril, aspirin. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: May result in renal function deterioration, particularly with high doses of aspirin,in elderly or volume depleted individuals.

• perphenazine

  perphenazine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  perphenazine, phenylephrine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.

• perphenazine

  chlorpheniramine and perphenazine both increase sedation. Use Caution/Monitor.

• phendimetrazine

  phendimetrazine and phenylephrine both decrease sedation. Use Caution/Monitor.
  
  chlorpheniramine increases and phendimetrazine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  phendimetrazine and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• phenelzine

  phenelzine increases effects of chlorpheniramine by Other (see comment). Modify Therapy/Monitor Closely. Comment: Coadministration of phenelzine and antihistamines may result in additive CNS depressant effects. MAO inhibitors also prolong and intensify anticholinergic effects of antihistamines. .

• phenobarbital

  phenobarbital increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• phenindione

  phenindione and aspirin both increase anticoagulation. Modify Therapy/Monitor Closely.

• phenobarbital

  chlorpheniramine and phenobarbital both increase sedation. Use Caution/Monitor.

• phenoxybenzamine

  aspirin decreases effects of phenoxybenzamine by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.

• phentermine

  phentermine and phenylephrine both decrease sedation. Use Caution/Monitor.
  
  chlorpheniramine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  phentermine and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• phentolamine

  aspirin decreases effects of phentolamine by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.

• pholcodine

  pholcodine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• phenylephrine

  chlorpheniramine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• phenylephrine PO

  chlorpheniramine increases and phenylephrine PO decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. .

• pholcodine

  chlorpheniramine and pholcodine both increase sedation. Use Caution/Monitor.

• phytoestrogens

  aspirin and phytoestrogens both increase anticoagulation. Use Caution/Monitor.

• pimozide

  pimozide increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and pimozide both increase sedation. Use Caution/Monitor.

• pindolol

  pindolol and aspirin both increase serum potassium. Use Caution/Monitor.
  
  aspirin decreases effects of pindolol by pharmacodynamic antagonism. Use Caution/Monitor. Long term (>1 wk) NSAID use. NSAIDs decrease prostaglandin synthesis.
  
  pindolol increases effects of phenylephrine by pharmacodynamic synergism. Use Caution/Monitor. Risk of acute hypertensive episode (rare).

• pirbuterol

  aspirin increases and pirbuterol decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine increases and pirbuterol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  pirbuterol and phenylephrine both decrease sedation. Use Caution/Monitor.
  
  pirbuterol and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• piroxicam

  aspirin and piroxicam both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and piroxicam both increase serum potassium. Use Caution/Monitor.

• primidone

  primidone increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• pregabalin

  pregabalin, chlorpheniramine. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Coadministration of CNS depressants can result in serious, life-threatening, and fatal respiratory depression. Use lowest dose possible and monitor for respiratory depression and sedation.

• pivmecillinam

  pivmecillinam, aspirin. Either increases levels of the other by plasma protein binding competition. Use Caution/Monitor.
  
  pivmecillinam, aspirin. Either increases levels of the other by decreasing renal clearance. Use Caution/Monitor.

• potassium acid phosphate

  aspirin and potassium acid phosphate both increase serum potassium. Modify Therapy/Monitor Closely.

• potassium chloride

  aspirin and potassium chloride both increase serum potassium. Modify Therapy/Monitor Closely.

• potassium citrate

  aspirin and potassium citrate both increase serum potassium. Use Caution/Monitor.

• potassium iodide

  potassium iodide and aspirin both increase serum potassium. Use Caution/Monitor.

• prasugrel

  aspirin, prasugrel. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. The need for simultaneous use of low-dose aspirin and anticoagulant or antiplatelet agents are common for patients with cardiovascular disease; monitor closely.

• prazosin

  aspirin decreases effects of prazosin by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.

• prednisolone

  aspirin, prednisolone. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of GI ulceration.

• prednisone

  aspirin, prednisone. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of GI ulceration.

• primidone

  chlorpheniramine and primidone both increase sedation. Use Caution/Monitor.

• prochlorperazine

  chlorpheniramine and prochlorperazine both increase sedation. Use Caution/Monitor.
  
  prochlorperazine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  prochlorperazine, phenylephrine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.

• promazine

  promazine, phenylephrine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.

• promethazine

  chlorpheniramine and promethazine both increase sedation. Use Caution/Monitor.

• promethazine

  promethazine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  promethazine, phenylephrine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.

• propofol

  propofol increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  propofol and chlorpheniramine both increase sedation. Use Caution/Monitor.

• propranolol

  propranolol and aspirin both increase serum potassium. Use Caution/Monitor.
  
  aspirin decreases effects of propranolol by pharmacodynamic antagonism. Use Caution/Monitor. Long term (>1 wk) NSAID use. NSAIDs decrease prostaglandin synthesis.
  
  propranolol increases effects of phenylephrine by pharmacodynamic synergism. Use Caution/Monitor. Risk of acute hypertensive episode (rare).

• propylhexedrine

  phenylephrine and propylhexedrine both decrease sedation. Use Caution/Monitor.
  
  chlorpheniramine increases and propylhexedrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  phenylephrine and propylhexedrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• protamine

  protamine and aspirin both increase anticoagulation. Modify Therapy/Monitor Closely.

• protriptyline

  protriptyline increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• protriptyline

  chlorpheniramine and protriptyline both increase sedation. Use Caution/Monitor.

• pseudoephedrine

  phenylephrine and pseudoephedrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• quazepam

  chlorpheniramine and quazepam both increase sedation. Use Caution/Monitor.
  
  quazepam increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• quetiapine

  quetiapine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and quetiapine both increase sedation. Use Caution/Monitor.

• quinapril

  quinapril, aspirin. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: May result in renal function deterioration, particularly with high doses of aspirin, in elderly or volume depleted individuals.

• rasagiline

  rasagiline increases effects of phenylephrine by pharmacodynamic synergism. Use Caution/Monitor. Risk of acute hypertensive episode.

• ramelteon

  chlorpheniramine and ramelteon both increase sedation. Use Caution/Monitor.

• ramipril

  ramipril, aspirin. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: May result in renal function deterioration, particularly with high doses of aspirin, in elderly or volume depleted individuals.

• reishi

  aspirin and reishi both increase anticoagulation. Use Caution/Monitor.

• reteplase

  aspirin, reteplase. Either increases toxicity of the other by anticoagulation. Use Caution/Monitor. The need for simultaneous use of low-dose aspirin and anticoagulant or antiplatelet agents are common for patients with cardiovascular disease; monitor closely.

• risperidone

  risperidone increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and risperidone both increase sedation. Use Caution/Monitor.

• rivaroxaban

  aspirin, rivaroxaban. Either increases toxicity of the other by anticoagulation. Use Caution/Monitor. Both drugs have the potential to cause bleeding. The need for simultaneous use of low-dose aspirin (<100 mg/day) with anticoagulants are common for patients with cardiovascular disease, but may result in increased bleeding; monitor closely. Promptly evaluate any signs or symptoms of blood loss if treated concomitantly with low-dose aspirin. Avoid coadministration with chronic use of higher dose aspirin.

• safinamide

  phenylephrine and safinamide both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor. Monitor patients for hypertension if safinamide is prescribed concomitantly with prescription or nonprescription sympathomimetics, including nasal, oral, or ophthalmic decongestants and cold remedies.

• rivastigmine

  rivastigmine increases toxicity of aspirin by pharmacodynamic synergism. Use Caution/Monitor. Monitor patients for symptoms of active or occult gastrointestinal bleeding.

• rucaparib

  rucaparib will increase the level or effect of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Adjust dosage of CYP3A4 substrates, if clinically indicated.

• sacubitril/valsartan

  sacubitril/valsartan and aspirin both increase serum potassium. Use Caution/Monitor.
  
  sacubitril/valsartan, aspirin. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: May result in renal function deterioration, particularly in elderly or volume depleted individuals.
  
  aspirin decreases effects of sacubitril/valsartan by pharmacodynamic antagonism. Modify Therapy/Monitor Closely. NSAIDs decrease synthesis of vasodilating renal prostaglandins, and thus affect fluid homeostasis and may diminish antihypertensive effect.

• salicylates (non-asa)

  aspirin and salicylates (non-asa) both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and salicylates (non-asa) both increase serum potassium. Use Caution/Monitor.

• salmeterol

  chlorpheniramine increases and salmeterol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  aspirin increases and salmeterol decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  salmeterol and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  salmeterol and phenylephrine both decrease sedation. Use Caution/Monitor.

• salsalate

  aspirin and salsalate both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and salsalate both increase serum potassium. Use Caution/Monitor.

• scullcap

  scullcap increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• scullcap

  chlorpheniramine and scullcap both increase sedation. Use Caution/Monitor.

• saw palmetto

  saw palmetto increases toxicity of aspirin by unspecified interaction mechanism. Use Caution/Monitor. May increase risk of bleeding.

• secobarbital

  secobarbital increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and secobarbital both increase sedation. Use Caution/Monitor.

• selegiline

  selegiline increases effects of phenylephrine by pharmacodynamic synergism. Use Caution/Monitor. Risk of acute hypertensive episode.

• selumetinib

  aspirin and selumetinib both increase anticoagulation. Modify Therapy/Monitor Closely. An increased risk of bleeding may occur in patients taking a vitamin-K antagonist or an antiplatelet agent with selumetinib. Monitor for bleeding and INR or PT in patients coadministered a vitamin-K antagonist or an antiplatelet agent with selumetinib.

• serdexmethylphenidate/dexmethylphenidate

  serdexmethylphenidate/dexmethylphenidate and phenylephrine both decrease sedation. Use Caution/Monitor.
  
  serdexmethylphenidate/dexmethylphenidate and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• sertraline

  sertraline, aspirin. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of upper GI bleeding. SSRIs inhib. serotonin uptake by platelets.

• Siberian ginseng

  aspirin and Siberian ginseng both increase anticoagulation. Use Caution/Monitor.

• sevoflurane

  sevoflurane and chlorpheniramine both increase sedation. Use Caution/Monitor.

• shepherd's purse

  chlorpheniramine and shepherd's purse both increase sedation. Use Caution/Monitor.
  
  shepherd's purse increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• silodosin

  aspirin decreases effects of silodosin by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.

• solriamfetol

  phenylephrine and solriamfetol both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• sodium picosulfate/magnesium oxide/anhydrous citric acid

  aspirin, sodium picosulfate/magnesium oxide/anhydrous citric acid. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: May be associated with fluid and electrolyte imbalances.

• sodium sulfate/?magnesium sulfate/potassium chloride

  sodium sulfate/?magnesium sulfate/potassium chloride increases toxicity of aspirin by Other (see comment). Use Caution/Monitor. Comment: Coadministration with medications that cause fluid and electrolyte abnormalities may increase the risk of adverse events of seizure, arrhythmias, and renal impairment.

• sodium sulfate/potassium sulfate/magnesium sulfate

  sodium sulfate/potassium sulfate/magnesium sulfate increases toxicity of aspirin by Other (see comment). Use Caution/Monitor. Comment: Coadministration with medications that cause fluid and electrolyte abnormalities may increase the risk of adverse events of seizure, arrhythmias, and renal impairment.

• sotalol

  sotalol and aspirin both increase serum potassium. Use Caution/Monitor.
  
  aspirin decreases effects of sotalol by pharmacodynamic antagonism. Use Caution/Monitor. Long term (>1 wk) NSAID use. NSAIDs decrease prostaglandin synthesis.

• spironolactone

  spironolactone and aspirin both increase serum potassium. Modify Therapy/Monitor Closely.
  
  aspirin decreases effects of spironolactone by unspecified interaction mechanism. Use Caution/Monitor. When used concomitantly, spironolactone dose may need to be titrated to higher maintenance dose and the patient should be observed closely to determine if the desired effect is obtained.

• stiripentol

  stiripentol, chlorpheniramine. affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Stiripentol is a CYP3A4 inhibitor and inducer. Monitor CYP3A4 substrates coadministered with stiripentol for increased or decreased effects. CYP3A4 substrates may require dosage adjustment.

• succinylcholine

  aspirin and succinylcholine both increase serum potassium. Use Caution/Monitor.

• sufentanil

  sufentanil increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and sufentanil both increase sedation. Use Caution/Monitor.

• sulfamethoxazole

  aspirin, sulfamethoxazole. Either increases effects of the other by plasma protein binding competition. Use Caution/Monitor. Due to high protein binding capacity of both drugs, one may displace the other when coadministered leading to an enhanced effect of the displaced drug; risk is low with low dose aspirin.

• tapentadol

  tapentadol increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• sulfasalazine

  aspirin and sulfasalazine both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and sulfasalazine both increase serum potassium. Use Caution/Monitor.

• sulindac

  aspirin and sulindac both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and sulindac both increase serum potassium. Use Caution/Monitor.

• tafluprost

  tafluprost, aspirin. unspecified interaction mechanism. Use Caution/Monitor. There are conflicting reports from studies of either increased or decreased IOP when ophthalmic prostaglandins are coadministered with NSAIDs (either systemic or ophthalmic).

• tapentadol

  chlorpheniramine and tapentadol both increase sedation. Use Caution/Monitor.

• tazemetostat

  tazemetostat will decrease the level or effect of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• tecovirimat

  tecovirimat will decrease the level or effect of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Tecovirimat is a weak CYP3A4 inducer. Monitor sensitive CYP3A4 substrates for effectiveness if coadministered.

• telmisartan

  telmisartan and aspirin both increase serum potassium. Use Caution/Monitor.
  
  aspirin decreases effects of telmisartan by pharmacodynamic antagonism. Modify Therapy/Monitor Closely. NSAIDs decrease synthesis of vasodilating renal prostaglandins, and thus affect fluid homeostasis and may diminish antihypertensive effect.
  
  telmisartan, aspirin. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: May result in renal function deterioration, particularly in elderly or volume depleted individuals.

• temazepam

  temazepam increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and temazepam both increase sedation. Use Caution/Monitor.

• temocillin

  temocillin, aspirin. Either increases levels of the other by plasma protein binding competition. Use Caution/Monitor.
  
  temocillin, aspirin. Either increases levels of the other by decreasing renal clearance. Use Caution/Monitor.

• terbutaline

  terbutaline and phenylephrine both decrease sedation. Use Caution/Monitor.
  
  terbutaline and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• tenecteplase

  aspirin, tenecteplase. Either increases toxicity of the other by anticoagulation. Use Caution/Monitor. The need for simultaneous use of low-dose aspirin and anticoagulant or antiplatelet agents are common for patients with cardiovascular disease; monitor closely.

• terazosin

  aspirin decreases effects of terazosin by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.

• terbutaline

  chlorpheniramine increases and terbutaline decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  aspirin increases and terbutaline decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• thioridazine

  thioridazine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  thioridazine, phenylephrine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.
  
  chlorpheniramine and thioridazine both increase sedation. Use Caution/Monitor.

• thiothixene

  thiothixene increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• thiothixene

  chlorpheniramine and thiothixene both increase sedation. Use Caution/Monitor.

• ticagrelor

  aspirin, ticagrelor. Other (see comment). Use Caution/Monitor. Comment: Maintenance doses of aspirin above 100 mg decreases effectiveness of ticagrelor. Therefore, after the initial loading dose of aspirin (usually 325 mg), use ticagrelor with a maintenance dose of aspirin of 75-100 mg.

• ticarcillin

  ticarcillin, aspirin. Either increases levels of the other by plasma protein binding competition. Use Caution/Monitor.
  
  ticarcillin, aspirin. Either increases levels of the other by decreasing renal clearance. Use Caution/Monitor.

• timolol

  timolol and aspirin both increase serum potassium. Use Caution/Monitor.
  
  timolol increases effects of phenylephrine by pharmacodynamic synergism. Use Caution/Monitor. Risk of acute hypertensive episode (rare).
  
  aspirin decreases effects of timolol by pharmacodynamic antagonism. Use Caution/Monitor. Long term (>1 wk) NSAID use. NSAIDs decrease prostaglandin synthesis.

• tirofiban

  aspirin, tirofiban. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. The need for simultaneous use of low-dose aspirin and anticoagulant or antiplatelet agents are common for patients with cardiovascular disease; monitor closely.

• topiramate

  topiramate increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.

• tobramycin inhaled

  tobramycin inhaled and aspirin both increase nephrotoxicity and/or ototoxicity. Modify Therapy/Monitor Closely. Avoid concurrent or sequential use to decrease risk for ototoxicity

• tolazamide

  aspirin increases effects of tolazamide by unknown mechanism. Use Caution/Monitor. Risk of hypoglycemia.

• tolbutamide

  aspirin increases effects of tolbutamide by unknown mechanism. Use Caution/Monitor. Risk of hypoglycemia.

• tolfenamic acid

  aspirin and tolfenamic acid both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and tolfenamic acid both increase serum potassium. Use Caution/Monitor.

• tolmetin

  aspirin and tolmetin both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and tolmetin both increase serum potassium. Use Caution/Monitor.

• tolvaptan

  aspirin and tolvaptan both increase serum potassium. Use Caution/Monitor.

• topiramate

  chlorpheniramine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• torsemide

  aspirin increases and torsemide decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• tramadol

  chlorpheniramine and tramadol both increase sedation. Use Caution/Monitor.
  
  tramadol increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• trandolapril

  trandolapril, aspirin. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: May result in renal function deterioration, particularly with high dose aspirin, in elderly and volume depleted.

• trazodone

  trazodone increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• travoprost ophthalmic

  travoprost ophthalmic, aspirin. unspecified interaction mechanism. Use Caution/Monitor. There are conflicting reports from studies of either increased or decreased IOP when ophthalmic prostaglandins are coadministered with NSAIDs (either systemic or ophthalmic).

• trazodone

  chlorpheniramine and trazodone both increase sedation. Use Caution/Monitor.
  
  trazodone, aspirin. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of upper GI bleeding. SSRIs inhib. serotonin uptake by platelets.

• triamcinolone acetonide injectable suspension

  aspirin, triamcinolone acetonide injectable suspension. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Aspirin in conjunction with corticosteroids in hypoprothrombinemia should used with caution. Clearance of salicylates may increase with concurrent use of corticosteroids.

• triazolam

  triazolam increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and triazolam both increase sedation. Use Caution/Monitor.

• triamterene

  triamterene and aspirin both increase serum potassium. Modify Therapy/Monitor Closely.

• triclofos

  triclofos increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• triclofos

  chlorpheniramine and triclofos both increase sedation. Use Caution/Monitor.

• trifluoperazine

  chlorpheniramine and trifluoperazine both increase sedation. Use Caution/Monitor.
  
  trifluoperazine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  trifluoperazine, phenylephrine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.

• trimipramine

  trimipramine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and trimipramine both increase sedation. Use Caution/Monitor.

• triprolidine

  triprolidine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and triprolidine both increase sedation. Use Caution/Monitor.

• valerian

  valerian increases effects of chlorpheniramine by pharmacodynamic synergism. Use Caution/Monitor. May enhance CNS depression.

• xylometazoline

  phenylephrine and xylometazoline both decrease sedation. Use Caution/Monitor.
  
  phenylephrine and xylometazoline both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• valproic acid

  aspirin increases levels of valproic acid by plasma protein binding competition. Use Caution/Monitor.

• valsartan

  valsartan and aspirin both increase serum potassium. Use Caution/Monitor.
  
  aspirin decreases effects of valsartan by pharmacodynamic antagonism. Modify Therapy/Monitor Closely. NSAIDs decrease synthesis of vasodilating renal prostaglandins, and thus affect fluid homeostasis and may diminish antihypertensive effect.
  
  valsartan, aspirin. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: May result in renal function deterioration, particularly in elderly or volume depleted individuals.

• venlafaxine

  venlafaxine, aspirin. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of upper GI bleeding. SSRIs inhib. serotonin uptake by platelets.

• voclosporin

  voclosporin, aspirin. Either increases toxicity of the other by nephrotoxicity and/or ototoxicity. Modify Therapy/Monitor Closely. Coadministration with drugs associated with nephrotoxicity may increase the risk for acute and/or chronic nephrotoxicity.

• vorapaxar

  aspirin, vorapaxar. Either increases effects of the other by anticoagulation. Use Caution/Monitor. Coadministration of anticoagulants, antiplatelets, or other drug affecting coagulation should be monitored periodically due to potential increased risk of bleeding.
  
  aspirin, vorapaxar. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Additive antiplatelet effect may occur.

• vortioxetine

  aspirin, vortioxetine. Either increases effects of the other by anticoagulation. Use Caution/Monitor. Risk minimal with low-dose aspirin.

• warfarin

  aspirin increases effects of warfarin by anticoagulation. Modify Therapy/Monitor Closely. Avoid coadministration of chronic high-dose aspirin. Aspirin's antiplatelet properties may increase anticoagulation effect of warfarin. The need for simultaneous use of low-dose aspirin and warfarin is common for patients with cardiovascular disease. .

• xylometazoline

  chlorpheniramine increases and xylometazoline decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• yohimbine

  yohimbine and phenylephrine both decrease sedation. Use Caution/Monitor.
  
  phenylephrine and yohimbine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  chlorpheniramine increases and yohimbine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• zanubrutinib

  aspirin, zanubrutinib. Either increases effects of the other by anticoagulation. Modify Therapy/Monitor Closely. Zanubrutinib-induced cytopenias increases risk of hemorrhage. Coadministration of zanubritinib with antiplatelets or anticoagulants may further increase this risk.

• ziconotide

  ziconotide increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• ziconotide

  chlorpheniramine and ziconotide both increase sedation. Use Caution/Monitor.

• ziprasidone

  ziprasidone increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and ziprasidone both increase sedation. Use Caution/Monitor.

• zotepine

  aspirin decreases effects of zotepine by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.
  
  chlorpheniramine and zotepine both increase sedation. Use Caution/Monitor.

Minor (108)

• aceclofenac

  aceclofenac will increase the level or effect of aspirin by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• acemetacin

  acemetacin will increase the level or effect of aspirin by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• acyclovir

  aspirin will increase the level or effect of acyclovir by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• alendronate

  aspirin, alendronate. Either increases toxicity of the other by pharmacodynamic synergism. Minor/Significance Unknown. Increased risk of GI ulceration.

• alfuzosin

  alfuzosin, phenylephrine. Either decreases effects of the other by Mechanism: pharmacodynamic antagonism. Minor/Significance Unknown.

• aluminum hydroxide

  aluminum hydroxide, aspirin. Mechanism: passive renal tubular reabsorption due to increased pH. Minor/Significance Unknown. Salicylate levels increased at moderate doses; salicylate levels decreased at large doses (d/t increased renal excretion of unchanged salicylic acid).

• amikacin

  aspirin increases levels of amikacin by decreasing renal clearance. Minor/Significance Unknown. Interaction mainly occurs in preterm infants.

• aminohippurate sodium

  aspirin will increase the level or effect of aminohippurate sodium by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• anamu

  aspirin and anamu both increase anticoagulation. Minor/Significance Unknown.

• ascorbic acid

  ascorbic acid will increase the level or effect of aspirin by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.
  
  aspirin decreases levels of ascorbic acid by increasing renal clearance. Minor/Significance Unknown.
  
  ascorbic acid increases levels of aspirin by decreasing renal clearance. Minor/Significance Unknown.

• asenapine

  asenapine, phenylephrine. Either decreases effects of the other by Mechanism: pharmacodynamic antagonism. Minor/Significance Unknown.

• ashwagandha

  ashwagandha increases effects of chlorpheniramine by pharmacodynamic synergism. Minor/Significance Unknown. May enhance CNS depression.

• balsalazide

  aspirin will increase the level or effect of balsalazide by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• bendroflumethiazide

  bendroflumethiazide will increase the level or effect of aspirin by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• bismuth subsalicylate

  bismuth subsalicylate increases effects of aspirin by pharmacodynamic synergism. Minor/Significance Unknown.

• brimonidine

  brimonidine increases effects of chlorpheniramine by pharmacodynamic synergism. Minor/Significance Unknown. Increased CNS depression.

• bumetanide

  aspirin, bumetanide. Other (see comment). Minor/Significance Unknown. Comment: Salicylates are less likely than other NSAIDs to interact w/bumetanide.

• calcium carbonate

  calcium carbonate, aspirin. Mechanism: passive renal tubular reabsorption due to increased pH. Minor/Significance Unknown. Salicylate levels increased at moderate doses; salicylate levels decreased at large doses (d/t increased renal excretion of unchanged salicylic acid).

• cefadroxil

  cefadroxil will increase the level or effect of aspirin by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• cefamandole

  cefamandole will increase the level or effect of aspirin by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• cefepime

  cefepime will increase the level or effect of aspirin by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• cefixime

  cefixime will increase the level or effect of aspirin by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• cefpirome

  cefpirome will increase the level or effect of aspirin by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• cefprozil

  cefprozil will increase the level or effect of aspirin by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• ceftazidime

  ceftazidime will increase the level or effect of aspirin by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• ceftibuten

  ceftibuten will increase the level or effect of aspirin by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• celecoxib

  aspirin will increase the level or effect of celecoxib by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• cephalexin

  cephalexin will increase the level or effect of aspirin by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• chlorothiazide

  chlorothiazide will increase the level or effect of aspirin by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• chlorpropamide

  aspirin will increase the level or effect of chlorpropamide by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.
  
  aspirin increases effects of chlorpropamide by plasma protein binding competition. Minor/Significance Unknown. Large dose of salicylate.

• chlorthalidone

  chlorthalidone will increase the level or effect of aspirin by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• choline magnesium trisalicylate

  aspirin will increase the level or effect of choline magnesium trisalicylate by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• chromium

  aspirin increases levels of chromium by unspecified interaction mechanism. Minor/Significance Unknown.

• cortisone

  cortisone decreases levels of aspirin by increasing renal clearance. Minor/Significance Unknown.

• creatine

  creatine, aspirin. Mechanism: pharmacodynamic synergism. Minor/Significance Unknown. (Theoretical interaction) Combination may have additive nephrotoxic effects.

• cyanocobalamin

  aspirin decreases levels of cyanocobalamin by inhibition of GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown.

• cyclopenthiazide

  cyclopenthiazide will increase the level or effect of aspirin by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• danshen

  aspirin and danshen both increase anticoagulation. Minor/Significance Unknown.

• deflazacort

  deflazacort decreases levels of aspirin by increasing renal clearance. Minor/Significance Unknown.

• desmopressin

  desmopressin increases effects of phenylephrine by pharmacodynamic synergism. Minor/Significance Unknown.

• devil's claw

  aspirin and devil's claw both increase anticoagulation. Minor/Significance Unknown.

• dexamethasone

  dexamethasone decreases levels of aspirin by increasing renal clearance. Minor/Significance Unknown.

• diclofenac

  aspirin will increase the level or effect of diclofenac by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• diclofenac topical

  diclofenac topical, aspirin. Either increases effects of the other by pharmacodynamic synergism. Minor/Significance Unknown. Although low, there is systemic exposure to diclofenac topical; theoretically, concomitant administration with systemic NSAIDS or aspirin may result in increased NSAID adverse effects.

• diflunisal

  aspirin will increase the level or effect of diflunisal by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• diltiazem

  diltiazem increases effects of aspirin by unknown mechanism. Minor/Significance Unknown. Enhanced antiplatelet activity.

• doxazosin

  doxazosin, phenylephrine. Either decreases effects of the other by Mechanism: pharmacodynamic antagonism. Minor/Significance Unknown.

• eplerenone

  aspirin decreases effects of eplerenone by pharmacodynamic antagonism. Minor/Significance Unknown. NSAIDs decrease prostaglandin synthesis.

• ethanol

  ethanol increases toxicity of aspirin by pharmacodynamic synergism. Minor/Significance Unknown. Increased risk of GI bleeding.

• etodolac

  aspirin will increase the level or effect of etodolac by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• eucalyptus

  eucalyptus increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Minor/Significance Unknown.
  
  chlorpheniramine and eucalyptus both increase sedation. Minor/Significance Unknown.

• fenbufen

  aspirin will increase the level or effect of fenbufen by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• moxisylyte

  moxisylyte, phenylephrine. Either decreases effects of the other by Mechanism: pharmacodynamic antagonism. Minor/Significance Unknown.

• fenoprofen

  aspirin will increase the level or effect of fenoprofen by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• feverfew

  aspirin decreases effects of feverfew by pharmacodynamic antagonism. Minor/Significance Unknown.

• fludrocortisone

  fludrocortisone decreases levels of aspirin by increasing renal clearance. Minor/Significance Unknown.

• flurbiprofen

  aspirin will increase the level or effect of flurbiprofen by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• folic acid

  aspirin decreases levels of folic acid by inhibition of GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown.

• furosemide

  aspirin decreases effects of furosemide by pharmacodynamic antagonism. Minor/Significance Unknown. NSAIDs decrease prostaglandin synthesis.

• ganciclovir

  aspirin will increase the level or effect of ganciclovir by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• gentamicin

  aspirin increases levels of gentamicin by decreasing renal clearance. Minor/Significance Unknown. Interaction mainly occurs in preterm infants.

• glimepiride

  aspirin increases effects of glimepiride by plasma protein binding competition. Minor/Significance Unknown. Large dose of salicylate.

• glipizide

  aspirin increases effects of glipizide by plasma protein binding competition. Minor/Significance Unknown. Large dose of salicylate.

• glyburide

  aspirin increases effects of glyburide by plasma protein binding competition. Minor/Significance Unknown. Large dose of salicylate.

• hydrochlorothiazide

  hydrochlorothiazide will increase the level or effect of aspirin by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• hydrocortisone

  hydrocortisone decreases levels of aspirin by increasing renal clearance. Minor/Significance Unknown.

• ibuprofen

  aspirin will increase the level or effect of ibuprofen by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• imidapril

  aspirin decreases effects of imidapril by pharmacodynamic antagonism. Minor/Significance Unknown. NSAIDs decrease prostaglandin synthesis.

• indapamide

  indapamide will increase the level or effect of aspirin by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• indomethacin

  aspirin will increase the level or effect of indomethacin by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• ketoprofen

  aspirin will increase the level or effect of ketoprofen by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• ketorolac

  aspirin will increase the level or effect of ketorolac by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• ketorolac intranasal

  aspirin will increase the level or effect of ketorolac intranasal by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• L-methylfolate

  aspirin decreases levels of L-methylfolate by inhibition of GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown.

• levoketoconazole

  levoketoconazole will increase the level or effect of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
  
  aspirin will decrease the level or effect of levoketoconazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• lornoxicam

  aspirin will increase the level or effect of lornoxicam by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• nettle

  nettle increases effects of chlorpheniramine by pharmacodynamic synergism. Minor/Significance Unknown. (High dose nettle; theoretical interaction) May enhance CNS depression.

• meclofenamate

  aspirin will increase the level or effect of meclofenamate by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• mefenamic acid

  aspirin will increase the level or effect of mefenamic acid by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• meloxicam

  aspirin will increase the level or effect of meloxicam by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• mesalamine

  aspirin will increase the level or effect of mesalamine by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• methyclothiazide

  methyclothiazide will increase the level or effect of aspirin by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• methylprednisolone

  methylprednisolone decreases levels of aspirin by increasing renal clearance. Minor/Significance Unknown.

• metolazone

  metolazone will increase the level or effect of aspirin by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• nabumetone

  aspirin will increase the level or effect of nabumetone by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• naproxen

  aspirin will increase the level or effect of naproxen by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• neomycin PO

  aspirin increases levels of neomycin PO by decreasing renal clearance. Minor/Significance Unknown. Interaction mainly occurs in preterm infants.

• noni juice

  aspirin and noni juice both increase serum potassium. Minor/Significance Unknown.

• ofloxacin

  ofloxacin, aspirin. Other (see comment). Minor/Significance Unknown. Comment: Risk of CNS stimulation/seizure. Mechanism: Displacement of GABA from receptors in brain.

• oxaprozin

  aspirin will increase the level or effect of oxaprozin by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• parecoxib

  aspirin will increase the level or effect of parecoxib by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• paromomycin

  aspirin increases levels of paromomycin by decreasing renal clearance. Minor/Significance Unknown. Interaction mainly occurs in preterm infants.

• penicillin VK

  penicillin VK, aspirin. Either increases levels of the other by decreasing renal clearance. Minor/Significance Unknown.

• pentazocine

  aspirin, pentazocine. Either increases toxicity of the other by pharmacodynamic synergism. Minor/Significance Unknown. Possible risk of renal papillary necrosis w/chronic Tx.

• phenoxybenzamine

  phenoxybenzamine, phenylephrine. Either decreases effects of the other by Mechanism: pharmacodynamic antagonism. Minor/Significance Unknown.

• phentolamine

  phentolamine, phenylephrine. Either decreases effects of the other by Mechanism: pharmacodynamic antagonism. Minor/Significance Unknown.

• piperacillin

  piperacillin, aspirin. Either increases effects of the other by receptor binding competition. Minor/Significance Unknown. Salicylic acid could be displaced from protein binding sites or it could itself displace other protein-bound drugs and result in an enhanced effect of the displaced drug.

• piroxicam

  aspirin will increase the level or effect of piroxicam by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• prazosin

  prazosin, phenylephrine. Either decreases effects of the other by Mechanism: pharmacodynamic antagonism. Minor/Significance Unknown.

• prednisolone

  prednisolone decreases levels of aspirin by increasing renal clearance. Minor/Significance Unknown.

• prednisone

  prednisone decreases levels of aspirin by increasing renal clearance. Minor/Significance Unknown.

• ribociclib

  ribociclib will increase the level or effect of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• rose hips

  rose hips will increase the level or effect of aspirin by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.
  
  aspirin decreases levels of rose hips by increasing renal clearance. Minor/Significance Unknown.
  
  rose hips increases levels of aspirin by decreasing renal clearance. Minor/Significance Unknown.

• sage

  sage increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Minor/Significance Unknown.
  
  chlorpheniramine and sage both increase sedation. Minor/Significance Unknown.

• Siberian ginseng

  Siberian ginseng increases effects of chlorpheniramine by pharmacodynamic synergism. Minor/Significance Unknown. May enhance CNS depression.

• silodosin

  silodosin, phenylephrine. Either decreases effects of the other by Mechanism: pharmacodynamic antagonism. Minor/Significance Unknown.

• salicylates (non-asa)

  aspirin will increase the level or effect of salicylates (non-asa) by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• terazosin

  terazosin, phenylephrine. Either decreases effects of the other by Mechanism: pharmacodynamic antagonism. Minor/Significance Unknown.

• abametapir

  Serious - Use Alternative (1)abametapir will increase the level or effect of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. For 2 weeks after abametapir application, avoid taking drugs that are CYP3A4 substrates. If not feasible, avoid use of abametapir.

• abciximab

  Monitor Closely (1)aspirin, abciximab. Either increases toxicity of the other by anticoagulation. Use Caution/Monitor. The need for simultaneous use of low-dose aspirin and anticoagulant or antiplatelet agents are common for patients with cardiovascular disease; monitor closely.

• abrocitinib

  Contraindicated (1)abrocitinib and aspirin both increase anticoagulation. Contraindicated. Antiplatelet drugs, except for low-dose aspirin (=81 mg qDay), during the first 3 months of treatment are contraindicated.

• acalabrutinib

  Monitor Closely (1)acalabrutinib increases effects of aspirin by anticoagulation. Modify Therapy/Monitor Closely. Coadministration of acalabrutinib with antiplatelets or anticoagulants may further increase risk of hemorrhage. Monitor for signs of bleeding and consider the benefit-risk of withholding acalabrutinib for 3-7 days presurgery and postsurgery depending upon the type of surgery and the risk of bleeding.

• acebutolol

  Monitor Closely (2)aspirin decreases effects of acebutolol by pharmacodynamic antagonism. Use Caution/Monitor. Long term (>1 wk) NSAID use. NSAIDs decrease prostaglandin synthesis.
  
  acebutolol and aspirin both increase serum potassium. Use Caution/Monitor.

• aceclofenac

  Monitor Closely (2)aceclofenac and aspirin both increase anticoagulation. Use Caution/Monitor.
  
  aceclofenac and aspirin both increase serum potassium. Use Caution/Monitor.Minor (1)aceclofenac will increase the level or effect of aspirin by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• acemetacin

  Monitor Closely (2)acemetacin and aspirin both increase anticoagulation. Use Caution/Monitor.
  
  acemetacin and aspirin both increase serum potassium. Use Caution/Monitor.Minor (1)acemetacin will increase the level or effect of aspirin by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• acetazolamide

  Monitor Closely (2)acetazolamide, aspirin. Either increases levels of the other by Other (see comment). Use Caution/Monitor. Comment: Carbonic anhydrase inhibitors (CAIs) and salicylates inhibit each other's renal tubular secretion, resulting in increased plasma levels. CAIs also shift salicylates from plasma to the CNS, leading to potential neurotoxicity.
  
  acetazolamide, aspirin. Mechanism: passive renal tubular reabsorption due to increased pH. Use Caution/Monitor. Salicylate levels increased at moderate doses; risk of CNS toxicity. Salicylate levels decreased at large doses (d/t increased renal excretion of unchanged salicylic acid).

• acyclovir

  Minor (1)aspirin will increase the level or effect of acyclovir by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• agrimony

  Monitor Closely (1)aspirin and agrimony both increase anticoagulation. Use Caution/Monitor.

• albuterol

  Monitor Closely (4)chlorpheniramine increases and albuterol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  albuterol and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  aspirin increases and albuterol decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  albuterol and phenylephrine both decrease sedation. Use Caution/Monitor.

• alendronate

  Minor (1)aspirin, alendronate. Either increases toxicity of the other by pharmacodynamic synergism. Minor/Significance Unknown. Increased risk of GI ulceration.

• alfalfa

  Monitor Closely (1)aspirin and alfalfa both increase anticoagulation. Use Caution/Monitor.

• alfentanil

  Monitor Closely (2)alfentanil increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and alfentanil both increase sedation. Use Caution/Monitor.

• alfuzosin

  Monitor Closely (1)aspirin decreases effects of alfuzosin by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.Minor (1)alfuzosin, phenylephrine. Either decreases effects of the other by Mechanism: pharmacodynamic antagonism. Minor/Significance Unknown.

• aliskiren

  Monitor Closely (1)aspirin will decrease the level or effect of aliskiren by Other (see comment). Use Caution/Monitor. In patients who are elderly, volume-depleted (including those on diuretic therapy), or with compromised renal function, coadministration of NSAIDs with drugs that affect RAAS may increase the risk of renal impairment (including acute renal failure) and cause loss of antihypertensive effect. Monitor renal function periodically.

• alprazolam

  Monitor Closely (2)chlorpheniramine and alprazolam both increase sedation. Use Caution/Monitor.
  
  alprazolam increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• alteplase

  Monitor Closely (1)aspirin, alteplase. Either increases toxicity of the other by anticoagulation. Use Caution/Monitor. The need for simultaneous use of low-dose aspirin and anticoagulant or antiplatelet agents are common for patients with cardiovascular disease; monitor closely.

• aluminum hydroxide

  Minor (1)aluminum hydroxide, aspirin. Mechanism: passive renal tubular reabsorption due to increased pH. Minor/Significance Unknown. Salicylate levels increased at moderate doses; salicylate levels decreased at large doses (d/t increased renal excretion of unchanged salicylic acid).

• American ginseng

  Monitor Closely (1)aspirin and American ginseng both increase anticoagulation. Use Caution/Monitor.

• amifampridine

  Monitor Closely (1)chlorpheniramine increases toxicity of amifampridine by Other (see comment). Modify Therapy/Monitor Closely. Comment: Amifampridine can cause seizures. Coadministration with drugs that lower seizure threshold may increase this risk.

• amikacin

  Minor (1)aspirin increases levels of amikacin by decreasing renal clearance. Minor/Significance Unknown. Interaction mainly occurs in preterm infants.

• amiloride

  Monitor Closely (1)amiloride and aspirin both increase serum potassium. Modify Therapy/Monitor Closely.

• aminohippurate sodium

  Minor (1)aspirin will increase the level or effect of aminohippurate sodium by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• amitriptyline

  Monitor Closely (2)amitriptyline increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and amitriptyline both increase sedation. Use Caution/Monitor.Serious - Use Alternative (1)amitriptyline, phenylephrine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.

• amobarbital

  Monitor Closely (3)amobarbital increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  amobarbital will decrease the level or effect of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  chlorpheniramine and amobarbital both increase sedation. Use Caution/Monitor.

• amoxapine

  Monitor Closely (2)amoxapine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and amoxapine both increase sedation. Use Caution/Monitor.Serious - Use Alternative (1)amoxapine, phenylephrine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.

• amoxicillin

  Monitor Closely (2)amoxicillin, aspirin. Either increases levels of the other by plasma protein binding competition. Use Caution/Monitor.
  
  amoxicillin, aspirin. Either increases levels of the other by decreasing renal clearance. Use Caution/Monitor.

• ampicillin

  Monitor Closely (1)ampicillin, aspirin. Either increases levels of the other by plasma protein binding competition. Use Caution/Monitor.

• anagrelide

  Monitor Closely (2)aspirin, anagrelide. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. The need for simultaneous use of low-dose aspirin and anticoagulant or antiplatelet agents are common for patients with cardiovascular disease; increases risk of bleeding; monitor closely.
  
  anagrelide, aspirin. Either increases toxicity of the other by Mechanism: pharmacodynamic synergism. Use Caution/Monitor. The need for simultaneous use of low-dose aspirin and anticoagulant or antiplatelet agents are common for patients with cardiovascular disease; increases risk of bleeding; monitor closely.

• anamu

  Minor (1)aspirin and anamu both increase anticoagulation. Minor/Significance Unknown.

• antithrombin alfa

  Monitor Closely (2)aspirin, antithrombin alfa. Either increases toxicity of the other by anticoagulation. Use Caution/Monitor. The need for simultaneous use of low-dose aspirin and anticoagulant or antiplatelet agents are common for patients with cardiovascular disease; monitor closely.
  
  antithrombin alfa and aspirin both increase anticoagulation. Modify Therapy/Monitor Closely.

• antithrombin III

  Monitor Closely (2)aspirin, antithrombin III. Either increases toxicity of the other by anticoagulation. Use Caution/Monitor. The need for simultaneous use of low-dose aspirin and anticoagulant or antiplatelet agents are common for patients with cardiovascular disease; monitor closely.
  
  antithrombin III and aspirin both increase anticoagulation. Modify Therapy/Monitor Closely.

• apalutamide

  Serious - Use Alternative (1)apalutamide will decrease the level or effect of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Coadministration of apalutamide, a strong CYP3A4 inducer, with drugs that are CYP3A4 substrates can result in lower exposure to these medications. Avoid or substitute another drug for these medications when possible. Evaluate for loss of therapeutic effect if medication must be coadministered. Adjust dose according to prescribing information if needed.

• apixaban

  Monitor Closely (1)aspirin and apixaban both increase anticoagulation. Modify Therapy/Monitor Closely. Both drugs have the potential to cause bleeding. The need for simultaneous use of low-dose aspirin (<100 mg/day) with anticoagulants are common for patients with cardiovascular disease, but may result in increased bleeding; monitor closely. Promptly evaluate any signs or symptoms of blood loss if treated concomitantly with low-dose aspiriin. Avoid coadministration with chronic use of higher dose aspirin. In 1 trial (APPRAISE-2), therapy was terminated because of significantly increased bleeding when apixaban was administered with dual antiplatelet therapy (eg, aspirin plus clopidogrel) compared with single antiplatelet treatment

• apomorphine

  Monitor Closely (1)chlorpheniramine and apomorphine both increase sedation. Use Caution/Monitor.

• arformoterol

  Monitor Closely (4)chlorpheniramine increases and arformoterol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  aspirin increases and arformoterol decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  arformoterol and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  arformoterol and phenylephrine both decrease sedation. Use Caution/Monitor.

• argatroban

  Monitor Closely (2)aspirin, argatroban. Either increases toxicity of the other by anticoagulation. Use Caution/Monitor. The need for simultaneous use of low-dose aspirin and anticoagulant or antiplatelet agents are common for patients with cardiovascular disease; monitor closely.
  
  argatroban and aspirin both increase anticoagulation. Modify Therapy/Monitor Closely.

• aripiprazole

  Monitor Closely (2)aripiprazole increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and aripiprazole both increase sedation. Use Caution/Monitor.

• armodafinil

  Monitor Closely (2)chlorpheniramine increases and armodafinil decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  armodafinil and phenylephrine both decrease sedation. Use Caution/Monitor.

• ascorbic acid

  Minor (3)ascorbic acid will increase the level or effect of aspirin by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.
  
  aspirin decreases levels of ascorbic acid by increasing renal clearance. Minor/Significance Unknown.
  
  ascorbic acid increases levels of aspirin by decreasing renal clearance. Minor/Significance Unknown.

• asenapine

  Monitor Closely (1)aspirin decreases effects of asenapine by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.Minor (1)asenapine, phenylephrine. Either decreases effects of the other by Mechanism: pharmacodynamic antagonism. Minor/Significance Unknown.

• ashwagandha

  Minor (1)ashwagandha increases effects of chlorpheniramine by pharmacodynamic synergism. Minor/Significance Unknown. May enhance CNS depression.

• atenolol

  Monitor Closely (2)aspirin decreases effects of atenolol by pharmacodynamic antagonism. Use Caution/Monitor. Long term (>1 wk) NSAID use. NSAIDs decrease prostaglandin synthesis.
  
  atenolol and aspirin both increase serum potassium. Use Caution/Monitor.

• atomoxetine

  Monitor Closely (1)atomoxetine, phenylephrine. Other (see comment). Use Caution/Monitor. Comment: Due to the potential for increases in blood pressure and heart rate, atomoxetine should be used cautiously with vasopressors such as phenylephrine.

• azelastine

  Monitor Closely (2)azelastine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  azelastine and chlorpheniramine both increase sedation. Use Caution/Monitor.

• azficel-T

  Monitor Closely (1)azficel-T, aspirin. Other (see comment). Use Caution/Monitor. Comment: Patients taking aspirin may experience increased bruising or bleeding at biopsy and/or injection sites. Concomitant use of aspirin is not recommended. .

• azilsartan

  Monitor Closely (2)aspirin, azilsartan. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: May result in renal function deterioration, particularly in elderly or volume depleted individuals.
  
  aspirin decreases effects of azilsartan by pharmacodynamic antagonism. Modify Therapy/Monitor Closely. NSAIDs decrease synthesis of vasodilating renal prostaglandins, and thus affect fluid homeostasis and may diminish antihypertensive effect.

• baclofen

  Monitor Closely (1)chlorpheniramine and baclofen both increase sedation. Use Caution/Monitor.

• balsalazide

  Minor (1)aspirin will increase the level or effect of balsalazide by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• belladonna and opium

  Monitor Closely (2)chlorpheniramine and belladonna and opium both increase sedation. Use Caution/Monitor.
  
  belladonna and opium increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• belzutifan

  Monitor Closely (1)belzutifan will decrease the level or effect of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. If unable to avoid coadministration of belzutifan with sensitive CYP3A4 substrates, consider increasing the sensitive CYP3A4 substrate dose in accordance with its prescribing information.

• bemiparin

  Monitor Closely (1)bemiparin and aspirin both increase anticoagulation. Modify Therapy/Monitor Closely.

• benazepril

  Monitor Closely (1)benazepril, aspirin. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: May result in renal function deterioration, particularly with high dose aspirin, in elderly or volume depleted individuals.Serious - Use Alternative (1)aspirin, benazepril. pharmacodynamic antagonism. Avoid or Use Alternate Drug. Coadministration may result in a significant decrease in renal function. NSAIDs may diminish the antihypertensive effect of ACE inhibitors. The mechanism of these interactions is likely related to the ability of NSAIDs to reduce the synthesis of vasodilating renal prostaglandins.

• bendroflumethiazide

  Monitor Closely (1)aspirin increases and bendroflumethiazide decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.Minor (1)bendroflumethiazide will increase the level or effect of aspirin by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• benperidol

  Monitor Closely (2)chlorpheniramine and benperidol both increase sedation. Use Caution/Monitor.
  
  benperidol increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• benzphetamine

  Monitor Closely (3)chlorpheniramine increases and benzphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  benzphetamine and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  benzphetamine and phenylephrine both decrease sedation. Use Caution/Monitor.

• betaxolol

  Monitor Closely (2)aspirin decreases effects of betaxolol by pharmacodynamic antagonism. Use Caution/Monitor. Long term (>1 wk) NSAID use. NSAIDs decrease prostaglandin synthesis.
  
  betaxolol and aspirin both increase serum potassium. Use Caution/Monitor.

• betrixaban

  Monitor Closely (1)aspirin, betrixaban. Either increases levels of the other by anticoagulation. Use Caution/Monitor.

• bimatoprost

  Monitor Closely (1)bimatoprost, aspirin. unspecified interaction mechanism. Use Caution/Monitor. There are conflicting reports from studies of either increased or decreased IOP when ophthalmic prostaglandins are coadministered with NSAIDs (either systemic or ophthalmic).

• bismuth subsalicylate

  Minor (1)bismuth subsalicylate increases effects of aspirin by pharmacodynamic synergism. Minor/Significance Unknown.

• bisoprolol

  Monitor Closely (2)aspirin decreases effects of bisoprolol by pharmacodynamic antagonism. Use Caution/Monitor. Long term (>1 wk) NSAID use. NSAIDs decrease prostaglandin synthesis.
  
  bisoprolol and aspirin both increase serum potassium. Use Caution/Monitor.

• bivalirudin

  Monitor Closely (2)aspirin, bivalirudin. Either increases toxicity of the other by anticoagulation. Use Caution/Monitor. The need for simultaneous use of low-dose aspirin and anticoagulant or antiplatelet agents are common for patients with cardiovascular disease; monitor closely.
  
  bivalirudin and aspirin both increase anticoagulation. Modify Therapy/Monitor Closely.

• brexanolone

  Monitor Closely (1)brexanolone, chlorpheniramine. Either increases toxicity of the other by sedation. Use Caution/Monitor.

• brimonidine

  Minor (1)brimonidine increases effects of chlorpheniramine by pharmacodynamic synergism. Minor/Significance Unknown. Increased CNS depression.

• brinzolamide

  Monitor Closely (1)brinzolamide, aspirin. Either increases levels of the other by Other (see comment). Use Caution/Monitor. Comment: Carbonic anhydrase inhibitors (CAIs) and salicylates inhibit each other's renal tubular secretion, resulting in increased plasma levels. CAIs also shift salicylates from plasma to the CNS, leading to potential neurotoxicity.

• bromocriptine

  Monitor Closely (1)bromocriptine, phenylephrine. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Hypertension, V tach.

• brompheniramine

  Monitor Closely (2)brompheniramine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  brompheniramine and chlorpheniramine both increase sedation. Use Caution/Monitor.

• bumetanide

  Monitor Closely (2)aspirin decreases effects of bumetanide by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.
  
  aspirin increases and bumetanide decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.Minor (1)aspirin, bumetanide. Other (see comment). Minor/Significance Unknown. Comment: Salicylates are less likely than other NSAIDs to interact w/bumetanide.

• buprenorphine

  Monitor Closely (1)chlorpheniramine and buprenorphine both increase sedation. Use Caution/Monitor.

• buprenorphine buccal

  Monitor Closely (2)chlorpheniramine and buprenorphine buccal both increase sedation. Use Caution/Monitor.
  
  buprenorphine buccal increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• butabarbital

  Monitor Closely (2)chlorpheniramine and butabarbital both increase sedation. Use Caution/Monitor.
  
  butabarbital increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• butalbital

  Monitor Closely (2)chlorpheniramine and butalbital both increase sedation. Use Caution/Monitor.
  
  butalbital increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• butorphanol

  Monitor Closely (2)chlorpheniramine and butorphanol both increase sedation. Use Caution/Monitor.
  
  butorphanol increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• cabergoline

  Serious - Use Alternative (1)cabergoline, phenylephrine. Mechanism: pharmacodynamic synergism. Contraindicated. Additive vasospasm; risk of hypertension.

• caffeine

  Monitor Closely (2)chlorpheniramine increases and caffeine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  caffeine and phenylephrine both decrease sedation. Use Caution/Monitor.

• calcium carbonate

  Minor (1)calcium carbonate, aspirin. Mechanism: passive renal tubular reabsorption due to increased pH. Minor/Significance Unknown. Salicylate levels increased at moderate doses; salicylate levels decreased at large doses (d/t increased renal excretion of unchanged salicylic acid).

• calcium/magnesium/potassium/sodium oxybates

  Serious - Use Alternative (1)chlorpheniramine, calcium/magnesium/potassium/sodium oxybates. Either increases effects of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Profound sedation, respiratory depression, coma, and death may result if coadministered. Reserve concomitant prescribing of these drugs in patients for whom other treatment options are inadequate. Limit dosages and durations to the minimum required. Monitor closely for signs of respiratory depression and sedation.

• candesartan

  Monitor Closely (3)candesartan, aspirin. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: May result in renal function deterioration, particularly in elderly or volume depleted individuals.
  
  aspirin decreases effects of candesartan by pharmacodynamic antagonism. Modify Therapy/Monitor Closely. NSAIDs decrease synthesis of vasodilating renal prostaglandins, and thus affect fluid homeostasis and may diminish antihypertensive effect.
  
  candesartan and aspirin both increase serum potassium. Use Caution/Monitor.

• caplacizumab

  Serious - Use Alternative (1)caplacizumab, aspirin. Either increases effects of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug.

• captopril

  Monitor Closely (1)captopril, aspirin. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: May result in renal function deterioration, particularly with high dose aspirin, elderly or volume depleted individuals.Serious - Use Alternative (1)aspirin, captopril. pharmacodynamic antagonism. Avoid or Use Alternate Drug. Coadministration may result in a significant decrease in renal function. NSAIDs may diminish the antihypertensive effect of ACE inhibitors. The mechanism of these interactions is likely related to the ability of NSAIDs to reduce the synthesis of vasodilating renal prostaglandins.

• carbenoxolone

  Monitor Closely (1)aspirin increases and carbenoxolone decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• carbinoxamine

  Monitor Closely (2)carbinoxamine and chlorpheniramine both increase sedation. Use Caution/Monitor.
  
  carbinoxamine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• carisoprodol

  Monitor Closely (1)chlorpheniramine and carisoprodol both increase sedation. Use Caution/Monitor.

• carvedilol

  Monitor Closely (2)aspirin decreases effects of carvedilol by pharmacodynamic antagonism. Use Caution/Monitor. Long term (>1 wk) NSAID use. NSAIDs decrease prostaglandin synthesis.
  
  carvedilol and aspirin both increase serum potassium. Use Caution/Monitor.

• cefadroxil

  Minor (1)cefadroxil will increase the level or effect of aspirin by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• cefamandole

  Minor (1)cefamandole will increase the level or effect of aspirin by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• cefepime

  Minor (1)cefepime will increase the level or effect of aspirin by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• cefixime

  Minor (1)cefixime will increase the level or effect of aspirin by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• cefpirome

  Minor (1)cefpirome will increase the level or effect of aspirin by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• cefprozil

  Minor (1)cefprozil will increase the level or effect of aspirin by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• ceftazidime

  Minor (1)ceftazidime will increase the level or effect of aspirin by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• ceftibuten

  Minor (1)ceftibuten will increase the level or effect of aspirin by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• celecoxib

  Monitor Closely (2)aspirin and celecoxib both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and celecoxib both increase serum potassium. Use Caution/Monitor.Minor (1)aspirin will increase the level or effect of celecoxib by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• celiprolol

  Monitor Closely (2)aspirin decreases effects of celiprolol by pharmacodynamic antagonism. Use Caution/Monitor. Long term (>1 wk) NSAID use. NSAIDs decrease prostaglandin synthesis.
  
  celiprolol and aspirin both increase serum potassium. Use Caution/Monitor.

• cenobamate

  Monitor Closely (2)cenobamate, chlorpheniramine. Either increases effects of the other by sedation. Use Caution/Monitor.
  
  cenobamate will decrease the level or effect of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Increase dose of CYP3A4 substrate, as needed, when coadministered with cenobamate.

• cephalexin

  Minor (1)cephalexin will increase the level or effect of aspirin by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• chloral hydrate

  Monitor Closely (2)chlorpheniramine and chloral hydrate both increase sedation. Use Caution/Monitor.
  
  chloral hydrate increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• chlordiazepoxide

  Monitor Closely (2)chlorpheniramine and chlordiazepoxide both increase sedation. Use Caution/Monitor.
  
  chlordiazepoxide increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• chlorothiazide

  Monitor Closely (1)aspirin increases and chlorothiazide decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.Minor (1)chlorothiazide will increase the level or effect of aspirin by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• chlorpheniramine

  Monitor Closely (1)chlorpheniramine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• chlorpromazine

  Monitor Closely (3)chlorpheniramine and chlorpromazine both increase sedation. Use Caution/Monitor.
  
  chlorpromazine, phenylephrine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.
  
  chlorpromazine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• chlorpropamide

  Monitor Closely (1)aspirin increases effects of chlorpropamide by unknown mechanism. Use Caution/Monitor. Risk of hypoglycemia.Minor (2)aspirin will increase the level or effect of chlorpropamide by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.
  
  aspirin increases effects of chlorpropamide by plasma protein binding competition. Minor/Significance Unknown. Large dose of salicylate.

• chlorthalidone

  Monitor Closely (1)aspirin increases and chlorthalidone decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.Minor (1)chlorthalidone will increase the level or effect of aspirin by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• chlorzoxazone

  Monitor Closely (1)chlorpheniramine and chlorzoxazone both increase sedation. Use Caution/Monitor.

• choline magnesium trisalicylate

  Monitor Closely (2)aspirin and choline magnesium trisalicylate both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and choline magnesium trisalicylate both increase serum potassium. Use Caution/Monitor.Minor (1)aspirin will increase the level or effect of choline magnesium trisalicylate by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• chromium

  Minor (1)aspirin increases levels of chromium by unspecified interaction mechanism. Minor/Significance Unknown.

• cilostazol

  Monitor Closely (1)aspirin, cilostazol. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. The need for simultaneous use of low-dose aspirin and anticoagulant or antiplatelet agents are common for patients with cardiovascular disease; monitor closely.

• cinnamon

  Monitor Closely (1)aspirin and cinnamon both increase anticoagulation. Use Caution/Monitor.

• cinnarizine

  Monitor Closely (2)chlorpheniramine and cinnarizine both increase sedation. Use Caution/Monitor.
  
  cinnarizine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• ciprofloxacin

  Monitor Closely (1)aspirin decreases levels of ciprofloxacin by Other (see comment). Use Caution/Monitor. Comment: Buffered aspirin may decrease absorption of quinolones. Consider administering 2 hr before or 6 hr after, buffered aspirin administration.

• citalopram

  Monitor Closely (1)citalopram, aspirin. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of upper GI bleeding. If possible, avoid concurrent use.

• clemastine

  Monitor Closely (2)chlorpheniramine and clemastine both increase sedation. Use Caution/Monitor.
  
  clemastine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• clobazam

  Monitor Closely (1)chlorpheniramine, clobazam. Other (see comment). Use Caution/Monitor. Comment: Concomitant administration can increase the potential for CNS effects (e.g., increased sedation or respiratory depression).

• clomipramine

  Monitor Closely (3)clomipramine, aspirin. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of upper GI bleeding. Clomipramine inhib. serotonin uptake by platelets.
  
  chlorpheniramine and clomipramine both increase sedation. Use Caution/Monitor.
  
  clomipramine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.Serious - Use Alternative (1)clomipramine, phenylephrine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.

• clonazepam

  Monitor Closely (2)chlorpheniramine and clonazepam both increase sedation. Use Caution/Monitor.
  
  clonazepam increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• clopidogrel

  Monitor Closely (1)aspirin, clopidogrel. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. The need for simultaneous use of low-dose aspirin and anticoagulant or antiplatelet agents are common for patients with cardiovascular disease; monitor closely.

• clorazepate

  Monitor Closely (2)chlorpheniramine and clorazepate both increase sedation. Use Caution/Monitor.
  
  clorazepate increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• clozapine

  Monitor Closely (2)clozapine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and clozapine both increase sedation. Use Caution/Monitor.

• codeine

  Monitor Closely (2)chlorpheniramine and codeine both increase sedation. Use Caution/Monitor.
  
  codeine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• collagenase clostridium histolyticum

  Monitor Closely (1)aspirin increases toxicity of collagenase clostridium histolyticum by anticoagulation. Use Caution/Monitor. Collagenase clostridium histolyticum has high incidence of ecchymosis/contusion at injection site; avoid concomitant anticoagulants (except for low-dose aspirin, ie, up to 150 mg/day).

• cordyceps

  Monitor Closely (1)aspirin and cordyceps both increase anticoagulation. Use Caution/Monitor.

• cortisone

  Monitor Closely (1)aspirin, cortisone. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of GI ulceration.Minor (1)cortisone decreases levels of aspirin by increasing renal clearance. Minor/Significance Unknown.

• creatine

  Minor (1)creatine, aspirin. Mechanism: pharmacodynamic synergism. Minor/Significance Unknown. (Theoretical interaction) Combination may have additive nephrotoxic effects.

• crofelemer

  Monitor Closely (1)crofelemer increases levels of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Crofelemer has the potential to inhibit CYP3A4 at concentrations expected in the gut; unlikely to inhibit systemically because minimally absorbed.

• cyanocobalamin

  Minor (1)aspirin decreases levels of cyanocobalamin by inhibition of GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown.

• cyclizine

  Monitor Closely (2)cyclizine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and cyclizine both increase sedation. Use Caution/Monitor.

• cyclobenzaprine

  Monitor Closely (1)chlorpheniramine and cyclobenzaprine both increase sedation. Use Caution/Monitor.

• cyclopenthiazide

  Monitor Closely (1)aspirin increases and cyclopenthiazide decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.Minor (1)cyclopenthiazide will increase the level or effect of aspirin by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• cyproheptadine

  Monitor Closely (2)chlorpheniramine and cyproheptadine both increase sedation. Use Caution/Monitor.
  
  cyproheptadine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• dabigatran

  Monitor Closely (1)dabigatran and aspirin both increase anticoagulation. Modify Therapy/Monitor Closely. Both drugs have the potential to cause bleeding. The need for simultaneous use of low-dose aspirin (<100 mg/day) with anticoagulants are common for patients with cardiovascular disease, but may result in increased bleeding; monitor closely. Promptly evaluate any signs or symptoms of blood loss if treated concomitantly with low-dose aspirin. Avoid coadministration with chronic use of higher dose aspirin

• dabrafenib

  Monitor Closely (1)dabrafenib will decrease the level or effect of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely.

• dalteparin

  Monitor Closely (2)aspirin, dalteparin. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. The need for simultaneous use of low-dose aspirin and anticoagulant or antiplatelet agents are common for patients with cardiovascular disease; monitor closely.
  
  dalteparin and aspirin both increase anticoagulation. Modify Therapy/Monitor Closely.

• danshen

  Minor (1)aspirin and danshen both increase anticoagulation. Minor/Significance Unknown.

• dantrolene

  Monitor Closely (1)chlorpheniramine and dantrolene both increase sedation. Use Caution/Monitor.

• daridorexant

  Monitor Closely (1)chlorpheniramine and daridorexant both increase sedation. Modify Therapy/Monitor Closely. Coadministration increases risk of CNS depression, which can lead to additive impairment of psychomotor performance and cause daytime impairment.

• deferasirox

  Monitor Closely (1)deferasirox, aspirin. Other (see comment). Use Caution/Monitor. Comment: Combination may increase GI bleeding, ulceration and irritation. Use with caution.

• defibrotide

  Monitor Closely (1)defibrotide increases effects of aspirin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. Defibrotide may enhance effects of platelet inhibitors.

• deflazacort

  Monitor Closely (1)aspirin, deflazacort. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of GI ulceration.Minor (1)deflazacort decreases levels of aspirin by increasing renal clearance. Minor/Significance Unknown.

• desflurane

  Monitor Closely (1)desflurane and chlorpheniramine both increase sedation. Use Caution/Monitor.Serious - Use Alternative (2)desflurane increases toxicity of phenylephrine by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of V tach, HTN.
  
  desflurane increases levels of phenylephrine by decreasing metabolism. Contraindicated.

• desipramine

  Monitor Closely (2)chlorpheniramine and desipramine both increase sedation. Use Caution/Monitor.
  
  desipramine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.Serious - Use Alternative (1)desipramine, phenylephrine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.

• desirudin

  Monitor Closely (1)aspirin, desirudin. Either increases levels of the other by pharmacodynamic synergism. Use Caution/Monitor. The need for simultaneous use of low-dose aspirin and anticoagulant or antiplatelet agents are common for patients with cardiovascular disease; monitor closely.

• desmopressin

  Minor (1)desmopressin increases effects of phenylephrine by pharmacodynamic synergism. Minor/Significance Unknown.

• deutetrabenazine

  Monitor Closely (1)chlorpheniramine and deutetrabenazine both increase sedation. Use Caution/Monitor.

• devil's claw

  Minor (1)aspirin and devil's claw both increase anticoagulation. Minor/Significance Unknown.

• dexamethasone

  Monitor Closely (1)aspirin, dexamethasone. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of GI ulceration.Minor (1)dexamethasone decreases levels of aspirin by increasing renal clearance. Minor/Significance Unknown.

• dexchlorpheniramine

  Monitor Closely (2)dexchlorpheniramine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and dexchlorpheniramine both increase sedation. Use Caution/Monitor.

• dexfenfluramine

  Monitor Closely (3)chlorpheniramine increases and dexfenfluramine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  dexfenfluramine and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  dexfenfluramine and phenylephrine both decrease sedation. Use Caution/Monitor.

• dexmedetomidine

  Monitor Closely (2)dexmedetomidine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and dexmedetomidine both increase sedation. Use Caution/Monitor.

• dexmethylphenidate

  Monitor Closely (3)dexmethylphenidate and phenylephrine both decrease sedation. Use Caution/Monitor.
  
  chlorpheniramine increases and dexmethylphenidate decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  dexmethylphenidate and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• dextroamphetamine

  Monitor Closely (3)dextroamphetamine and phenylephrine both decrease sedation. Use Caution/Monitor.
  
  chlorpheniramine increases and dextroamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  dextroamphetamine and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• dextromoramide

  Monitor Closely (2)chlorpheniramine and dextromoramide both increase sedation. Use Caution/Monitor.
  
  dextromoramide increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• diamorphine

  Monitor Closely (2)chlorpheniramine and diamorphine both increase sedation. Use Caution/Monitor.
  
  diamorphine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• diazepam

  Monitor Closely (1)chlorpheniramine and diazepam both increase sedation. Use Caution/Monitor.

• diazepam intranasal

  Monitor Closely (1)diazepam intranasal, chlorpheniramine. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Coadministration may potentiate the CNS-depressant effects of each drug.

• dichlorphenamide

  Contraindicated (1)dichlorphenamide increases levels of aspirin by unknown mechanism. Contraindicated. Coadministration of dichlorphenamide with high-dose aspirin may increase salicylate levels. Anorexia, tachypnea, lethargy, and coma reported.

• diclofenac

  Monitor Closely (2)aspirin and diclofenac both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and diclofenac both increase serum potassium. Use Caution/Monitor.Minor (1)aspirin will increase the level or effect of diclofenac by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• diclofenac topical

  Minor (1)diclofenac topical, aspirin. Either increases effects of the other by pharmacodynamic synergism. Minor/Significance Unknown. Although low, there is systemic exposure to diclofenac topical; theoretically, concomitant administration with systemic NSAIDS or aspirin may result in increased NSAID adverse effects.

• dicloxacillin

  Monitor Closely (1)dicloxacillin, aspirin. Either increases levels of the other by plasma protein binding competition. Use Caution/Monitor.

• diethylpropion

  Monitor Closely (3)diethylpropion and phenylephrine both decrease sedation. Use Caution/Monitor.
  
  diethylpropion and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  chlorpheniramine increases and diethylpropion decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• difelikefalin

  Monitor Closely (1)difelikefalin and chlorpheniramine both increase sedation. Use Caution/Monitor.

• difenoxin hcl

  Monitor Closely (2)difenoxin hcl increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and difenoxin hcl both increase sedation. Use Caution/Monitor.

• diflunisal

  Monitor Closely (2)aspirin and diflunisal both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and diflunisal both increase serum potassium. Use Caution/Monitor.Minor (1)aspirin will increase the level or effect of diflunisal by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• digoxin

  Monitor Closely (1)aspirin and digoxin both increase serum potassium. Use Caution/Monitor.

• dihydroergotamine

  Serious - Use Alternative (1)dihydroergotamine, phenylephrine. Mechanism: pharmacodynamic synergism. Contraindicated. Additive vasospasm; risk of hypertension.

• dihydroergotamine intranasal

  Serious - Use Alternative (1)dihydroergotamine intranasal, phenylephrine. Mechanism: pharmacodynamic synergism. Contraindicated. Additive vasospasm; risk of hypertension.

• diltiazem

  Minor (1)diltiazem increases effects of aspirin by unknown mechanism. Minor/Significance Unknown. Enhanced antiplatelet activity.

• dimenhydrinate

  Monitor Closely (2)dimenhydrinate increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and dimenhydrinate both increase sedation. Use Caution/Monitor.

• diphenhydramine

  Monitor Closely (2)diphenhydramine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and diphenhydramine both increase sedation. Use Caution/Monitor.

• diphenoxylate hcl

  Monitor Closely (2)chlorpheniramine and diphenoxylate hcl both increase sedation. Use Caution/Monitor.
  
  diphenoxylate hcl increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• dipipanone

  Monitor Closely (2)chlorpheniramine and dipipanone both increase sedation. Use Caution/Monitor.
  
  dipipanone increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• dipyridamole

  Monitor Closely (1)aspirin, dipyridamole. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. The need for simultaneous use of low-dose aspirin and anticoagulant or antiplatelet agents are common for patients with cardiovascular disease; monitor closely.

• dobutamine

  Monitor Closely (4)chlorpheniramine increases and dobutamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  dobutamine and phenylephrine both decrease sedation. Use Caution/Monitor.
  
  aspirin increases and dobutamine decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  dobutamine and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• donepezil transdermal

  Monitor Closely (1)donepezil transdermal, chlorpheniramine. Either decreases effects of the other by pharmacodynamic antagonism. Use Caution/Monitor.

• dong quai

  Monitor Closely (1)aspirin and dong quai both increase anticoagulation. Use Caution/Monitor.

• dopamine

  Monitor Closely (3)chlorpheniramine increases and dopamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  dopamine and phenylephrine both decrease sedation. Use Caution/Monitor.
  
  dopamine and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• dopexamine

  Monitor Closely (4)aspirin increases and dopexamine decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine increases and dopexamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  dopexamine and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  dopexamine and phenylephrine both decrease sedation. Use Caution/Monitor.

• dosulepin

  Monitor Closely (1)chlorpheniramine and dosulepin both increase sedation. Use Caution/Monitor.

• doxapram

  Serious - Use Alternative (1)doxapram increases effects of phenylephrine by pharmacodynamic synergism. Avoid or Use Alternate Drug. Additive pressor effect.

• doxazosin

  Monitor Closely (1)aspirin decreases effects of doxazosin by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.Minor (1)doxazosin, phenylephrine. Either decreases effects of the other by Mechanism: pharmacodynamic antagonism. Minor/Significance Unknown.

• doxepin

  Monitor Closely (2)doxepin increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and doxepin both increase sedation. Use Caution/Monitor.Serious - Use Alternative (1)doxepin, phenylephrine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.

• doxylamine

  Monitor Closely (1)chlorpheniramine and doxylamine both increase sedation. Use Caution/Monitor.

• droperidol

  Monitor Closely (2)chlorpheniramine and droperidol both increase sedation. Use Caution/Monitor.
  
  droperidol increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• drospirenone

  Monitor Closely (1)drospirenone and aspirin both increase serum potassium. Modify Therapy/Monitor Closely.

• droxidopa

  Monitor Closely (1)phenylephrine and droxidopa both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor. May increase risk for supine hypertension

• duloxetine

  Monitor Closely (1)duloxetine, aspirin. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of upper GI bleeding. SSRIs inhib. serotonin uptake by platelets.

• edoxaban

  Monitor Closely (1)edoxaban, aspirin. Either increases toxicity of the other by anticoagulation. Modify Therapy/Monitor Closely. Both drugs have the potential to cause bleeding. The need for simultaneous use of low-dose aspirin (<100 mg/day) with anticoagulants are common for patients with cardiovascular disease, but may result in increased bleeding; monitor closely. Promptly evaluate any signs or symptoms of blood loss if treated concomitantly with low-dose aspirin. Avoid coadministration with chronic use of higher dose aspirin.

• efavirenz

  Monitor Closely (1)efavirenz will decrease the level or effect of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• elagolix

  Monitor Closely (1)elagolix will decrease the level or effect of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Elagolix is a weak-to-moderate CYP3A4 inducer. Monitor CYP3A substrates if coadministered. Consider increasing CYP3A substrate dose if needed.

• eluxadoline

  Serious - Use Alternative (1)chlorpheniramine, eluxadoline. Either increases effects of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Avoid coadministration with other drugs that cause constipation. Increases risk for constipation related serious adverse reactions.

• elvitegravir/cobicistat/emtricitabine/tenofovir DF

  Monitor Closely (2)elvitegravir/cobicistat/emtricitabine/tenofovir DF, aspirin. Either increases toxicity of the other by decreasing renal clearance. Modify Therapy/Monitor Closely. Toxicity may result from coadministration of emtricitabine and tenofovir with other drugs that are also primarily excreted by glomerular filtration and/or active tubular secretion including high-dose or multiple-dose NSAIDs; alternatives to NSAIDs should be considered.
  
  elvitegravir/cobicistat/emtricitabine/tenofovir DF increases levels of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. CYP3A4 substrates for which elevated plasma concentrations are associated with serious and/or life-threatening events.

• enalapril

  Monitor Closely (1)enalapril, aspirin. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: May result in renal function deterioration, particularly with high dose aspirin, in elderly or volume depleted individuals.Serious - Use Alternative (1)aspirin, enalapril. pharmacodynamic antagonism. Avoid or Use Alternate Drug. Coadministration may result in a significant decrease in renal function. NSAIDs may diminish the antihypertensive effect of ACE inhibitors. The mechanism of these interactions is likely related to the ability of NSAIDs to reduce the synthesis of vasodilating renal prostaglandins.

• enoxaparin

  Monitor Closely (2)enoxaparin and aspirin both increase anticoagulation. Use Caution/Monitor. Additive effects are intended when both drugs are prescribed as indicated for unstable angina, non-Q-wave MI, and STEMI
  
  aspirin, enoxaparin. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. The need for simultaneous use of low-dose aspirin and anticoagulant or antiplatelet agents are common for patients with cardiovascular disease; monitor closely.

• ephedrine

  Monitor Closely (5)aspirin increases and ephedrine decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  ephedrine, phenylephrine. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor.
  
  ephedrine and phenylephrine both decrease sedation. Use Caution/Monitor.
  
  chlorpheniramine increases and ephedrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  ephedrine and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• epinephrine

  Monitor Closely (4)epinephrine and phenylephrine both decrease sedation. Use Caution/Monitor.
  
  aspirin increases and epinephrine decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  epinephrine and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  chlorpheniramine increases and epinephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• epinephrine inhaled

  Monitor Closely (1)phenylephrine, epinephrine inhaled. Either increases effects of the other by sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• epinephrine racemic

  Monitor Closely (4)chlorpheniramine increases and epinephrine racemic decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  epinephrine racemic and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  aspirin increases and epinephrine racemic decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  epinephrine racemic and phenylephrine both decrease sedation. Use Caution/Monitor.

• eplerenone

  Minor (1)aspirin decreases effects of eplerenone by pharmacodynamic antagonism. Minor/Significance Unknown. NSAIDs decrease prostaglandin synthesis.

• epoprostenol

  Monitor Closely (1)aspirin and epoprostenol both increase anticoagulation. Use Caution/Monitor.

• eprosartan

  Monitor Closely (3)aspirin decreases effects of eprosartan by pharmacodynamic antagonism. Modify Therapy/Monitor Closely. NSAIDs decrease synthesis of vasodilating renal prostaglandins, and thus affect fluid homeostasis and may diminish antihypertensive effect.
  
  eprosartan and aspirin both increase serum potassium. Use Caution/Monitor.
  
  eprosartan, aspirin. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: May result in renal function deterioration, particularly in elderly or volume depleted individuals.

• eptifibatide

  Monitor Closely (1)aspirin, eptifibatide. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. The need for simultaneous use of low-dose aspirin and anticoagulant or antiplatelet agents are common for patients with cardiovascular disease; monitor closely.

• ergoloid mesylates

  Serious - Use Alternative (1)ergoloid mesylates, phenylephrine. Mechanism: pharmacodynamic synergism. Contraindicated. Additive vasospasm; risk of hypertension.

• ergotamine

  Serious - Use Alternative (1)ergotamine, phenylephrine. Mechanism: pharmacodynamic synergism. Contraindicated. Additive vasospasm; risk of hypertension.

• escitalopram

  Monitor Closely (1)escitalopram, aspirin. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of upper GI bleeding. SSRIs inhib. serotonin uptake by platelets.

• esketamine intranasal

  Monitor Closely (1)esketamine intranasal, chlorpheniramine. Either increases toxicity of the other by sedation. Modify Therapy/Monitor Closely.

• esmolol

  Monitor Closely (2)aspirin decreases effects of esmolol by pharmacodynamic antagonism. Use Caution/Monitor. Long term (>1 wk) NSAID use. NSAIDs decrease prostaglandin synthesis.
  
  esmolol and aspirin both increase serum potassium. Use Caution/Monitor.

• estazolam

  Monitor Closely (2)estazolam increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and estazolam both increase sedation. Use Caution/Monitor.

• ethacrynic acid

  Monitor Closely (1)aspirin increases and ethacrynic acid decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• ethanol

  Monitor Closely (2)ethanol increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and ethanol both increase sedation. Use Caution/Monitor.Minor (1)ethanol increases toxicity of aspirin by pharmacodynamic synergism. Minor/Significance Unknown. Increased risk of GI bleeding.

• ether

  Serious - Use Alternative (1)ether increases toxicity of phenylephrine by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of V tach, HTN.

• etodolac

  Monitor Closely (2)aspirin and etodolac both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and etodolac both increase serum potassium. Use Caution/Monitor.Minor (1)aspirin will increase the level or effect of etodolac by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• etomidate

  Monitor Closely (1)etomidate and chlorpheniramine both increase sedation. Use Caution/Monitor.Serious - Use Alternative (1)etomidate increases levels of phenylephrine by decreasing metabolism. Contraindicated.

• eucalyptus

  Minor (2)eucalyptus increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Minor/Significance Unknown.
  
  chlorpheniramine and eucalyptus both increase sedation. Minor/Significance Unknown.

• fedratinib

  Monitor Closely (1)fedratinib will increase the level or effect of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Adjust dose of drugs that are CYP3A4 substrates as necessary.

• fenbufen

  Monitor Closely (2)aspirin and fenbufen both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and fenbufen both increase serum potassium. Use Caution/Monitor.Minor (1)aspirin will increase the level or effect of fenbufen by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• fenfluramine

  Monitor Closely (3)fenfluramine and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  chlorpheniramine increases and fenfluramine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  fenfluramine and phenylephrine both decrease sedation. Use Caution/Monitor.

• fennel

  Monitor Closely (1)aspirin and fennel both increase anticoagulation. Use Caution/Monitor.

• fenoprofen

  Monitor Closely (2)aspirin and fenoprofen both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and fenoprofen both increase serum potassium. Use Caution/Monitor.Minor (1)aspirin will increase the level or effect of fenoprofen by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• fentanyl

  Monitor Closely (1)fentanyl, chlorpheniramine. Either increases toxicity of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Coadministration of fentanyl with anticholinergics may increase risk for urinary retention and/or severe constipation, which may lead to paralytic ileus.

• fentanyl intranasal

  Monitor Closely (1)fentanyl intranasal, chlorpheniramine. Either increases toxicity of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Coadministration of fentanyl with anticholinergics may increase risk for urinary retention and/or severe constipation, which may lead to paralytic ileus.

• fentanyl transdermal

  Monitor Closely (1)fentanyl transdermal, chlorpheniramine. Either increases toxicity of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Coadministration of fentanyl with anticholinergics may increase risk for urinary retention and/or severe constipation, which may lead to paralytic ileus.

• fentanyl transmucosal

  Monitor Closely (1)fentanyl transmucosal, chlorpheniramine. Either increases toxicity of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Coadministration of fentanyl with anticholinergics may increase risk for urinary retention and/or severe constipation, which may lead to paralytic ileus.

• feverfew

  Monitor Closely (1)aspirin and feverfew both increase anticoagulation. Use Caution/Monitor.Minor (1)aspirin decreases effects of feverfew by pharmacodynamic antagonism. Minor/Significance Unknown.

• fexinidazole

  Serious - Use Alternative (1)fexinidazole will increase the level or effect of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Fexinidazole inhibits CYP3A4. Coadministration may increase risk for adverse effects of CYP3A4 substrates.

• fish oil

  Monitor Closely (1)fish oil, aspirin. Other (see comment). Use Caution/Monitor. Comment: Patients taking fish oil and an anticoagulant or other drug affecting coagulation should be monitored periodically due to potential increased risk of bleeding. .

• fish oil triglycerides

  Monitor Closely (1)fish oil triglycerides will increase the level or effect of aspirin by anticoagulation. Use Caution/Monitor. Prolonged bleeding reported in patients taking antiplatelet agents or anticoagulants and oral omega-3 fatty acids. Periodically monitor bleeding time in patients receiving fish oil triglycerides and concomitant antiplatelet agents or anticoagulants.

• flibanserin

  Monitor Closely (1)chlorpheniramine and flibanserin both increase sedation. Modify Therapy/Monitor Closely. Risk for sedation increased if flibanserin is coadministration with other CNS depressants.

• fludrocortisone

  Monitor Closely (1)aspirin, fludrocortisone. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of GI ulceration.Minor (1)fludrocortisone decreases levels of aspirin by increasing renal clearance. Minor/Significance Unknown.

• fluoxetine

  Monitor Closely (1)fluoxetine, aspirin. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of upper GI bleeding. SSRIs inhib. serotonin uptake by platelets.

• fluphenazine

  Monitor Closely (3)fluphenazine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and fluphenazine both increase sedation. Use Caution/Monitor.
  
  fluphenazine, phenylephrine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.

• flurazepam

  Monitor Closely (2)chlorpheniramine and flurazepam both increase sedation. Use Caution/Monitor.
  
  flurazepam increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• flurbiprofen

  Monitor Closely (2)aspirin and flurbiprofen both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and flurbiprofen both increase serum potassium. Use Caution/Monitor.Minor (1)aspirin will increase the level or effect of flurbiprofen by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• fluvoxamine

  Monitor Closely (1)fluvoxamine, aspirin. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of upper GI bleeding SSRIs inhib. serotonin uptake by platelets.

• folic acid

  Minor (1)aspirin decreases levels of folic acid by inhibition of GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown.

• fondaparinux

  Monitor Closely (1)fondaparinux and aspirin both increase anticoagulation. Modify Therapy/Monitor Closely.

• formoterol

  Monitor Closely (4)chlorpheniramine increases and formoterol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  aspirin increases and formoterol decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  formoterol and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  formoterol and phenylephrine both decrease sedation. Use Caution/Monitor.

• forskolin

  Monitor Closely (1)aspirin and forskolin both increase anticoagulation. Use Caution/Monitor.

• fosinopril

  Monitor Closely (1)fosinopril, aspirin. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: May result in renal function deterioration, particularly with high dose aspirin, in elderly or volume depleted individuals.Serious - Use Alternative (1)aspirin, fosinopril. pharmacodynamic antagonism. Avoid or Use Alternate Drug. Coadministration may result in a significant decrease in renal function. NSAIDs may diminish the antihypertensive effect of ACE inhibitors. The mechanism of these interactions is likely related to the ability of NSAIDs to reduce the synthesis of vasodilating renal prostaglandins.

• fosphenytoin

  Monitor Closely (1)fosphenytoin will decrease the level or effect of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• furosemide

  Monitor Closely (1)aspirin increases and furosemide decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.Minor (1)aspirin decreases effects of furosemide by pharmacodynamic antagonism. Minor/Significance Unknown. NSAIDs decrease prostaglandin synthesis.

• gabapentin

  Monitor Closely (1)gabapentin, chlorpheniramine. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Coadministration of CNS depressants can result in serious, life-threatening, and fatal respiratory depression. Use lowest dose possible and monitor for respiratory depression and sedation.

• gabapentin enacarbil

  Monitor Closely (1)gabapentin enacarbil, chlorpheniramine. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Coadministration of CNS depressants can result in serious, life-threatening, and fatal respiratory depression. Use lowest dose possible and monitor for respiratory depression and sedation.

• ganaxolone

  Monitor Closely (1)chlorpheniramine and ganaxolone both increase sedation. Use Caution/Monitor.

• ganciclovir

  Minor (1)aspirin will increase the level or effect of ganciclovir by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• garlic

  Monitor Closely (1)aspirin and garlic both increase anticoagulation. Use Caution/Monitor.

• gentamicin

  Monitor Closely (1)aspirin increases and gentamicin decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.Minor (1)aspirin increases levels of gentamicin by decreasing renal clearance. Minor/Significance Unknown. Interaction mainly occurs in preterm infants.

• ginger

  Monitor Closely (1)aspirin and ginger both increase anticoagulation. Use Caution/Monitor.

• ginkgo biloba

  Monitor Closely (1)aspirin and ginkgo biloba both increase anticoagulation. Use Caution/Monitor.

• glimepiride

  Monitor Closely (1)aspirin increases effects of glimepiride by unknown mechanism. Use Caution/Monitor. Risk of hypoglycemia.Minor (1)aspirin increases effects of glimepiride by plasma protein binding competition. Minor/Significance Unknown. Large dose of salicylate.

• glipizide

  Monitor Closely (1)aspirin increases effects of glipizide by unknown mechanism. Use Caution/Monitor. Risk of hypoglycemia.Minor (1)aspirin increases effects of glipizide by plasma protein binding competition. Minor/Significance Unknown. Large dose of salicylate.

• glyburide

  Monitor Closely (1)aspirin increases effects of glyburide by unknown mechanism. Use Caution/Monitor. Risk of hypoglycemia.Minor (1)aspirin increases effects of glyburide by plasma protein binding competition. Minor/Significance Unknown. Large dose of salicylate.

• glycopyrronium tosylate topical

  Monitor Closely (1)glycopyrronium tosylate topical, chlorpheniramine. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Coadministration of glycopyrronium tosylate topical with other anticholinergic medications may result in additive anticholinergic adverse effects.

• gotu kola

  Monitor Closely (1)gotu kola increases effects of chlorpheniramine by pharmacodynamic synergism. Use Caution/Monitor. May enhance CNS depression.

• green tea

  Monitor Closely (1)green tea increases effects of aspirin by pharmacodynamic synergism. Use Caution/Monitor. (Theoretical, due to caffeine content). Combination may increase risk of bleeding.

• griseofulvin

  Monitor Closely (1)griseofulvin decreases levels of aspirin by unknown mechanism. Use Caution/Monitor.

• haloperidol

  Monitor Closely (2)haloperidol increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and haloperidol both increase sedation. Use Caution/Monitor.

• hawthorn

  Monitor Closely (1)hawthorn increases effects of chlorpheniramine by pharmacodynamic synergism. Use Caution/Monitor. May enhance CNS depression.

• heparin

  Monitor Closely (2)aspirin, heparin. Either increases toxicity of the other by anticoagulation. Use Caution/Monitor. The need for simultaneous use of low-dose aspirin and anticoagulant or antiplatelet agents are common for patients with cardiovascular disease; monitor closely.
  
  heparin and aspirin both increase anticoagulation. Modify Therapy/Monitor Closely.

• hops

  Monitor Closely (1)hops increases effects of chlorpheniramine by pharmacodynamic synergism. Use Caution/Monitor. May enhance CNS depression.

• horse chestnut seed

  Monitor Closely (1)aspirin and horse chestnut seed both increase anticoagulation. Use Caution/Monitor.

• hyaluronidase

  Monitor Closely (2)chlorpheniramine decreases effects of hyaluronidase by Other (see comment). Use Caution/Monitor. Comment: Antihistamines, when given in large systemic doses, may render tissues partially resistant to the action of hyaluronidase. Patients may require larger amounts of hyaluronidase for equivalent dispersing effect.
  
  aspirin decreases effects of hyaluronidase by Other (see comment). Use Caution/Monitor. Comment: Salicylates, when given in large systemic doses, may render tissues partially resistant to the action of hyaluronidase. Patients may require larger amounts of hyaluronidase for equivalent dispersing effect.

• hydralazine

  Monitor Closely (2)aspirin decreases effects of hydralazine by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.
  
  hydralazine, phenylephrine. Mechanism: pharmacodynamic antagonism. Use Caution/Monitor. Sympathomimetics can antagonize the activity of some antihypertensive agents.

• hydrochlorothiazide

  Monitor Closely (1)aspirin increases and hydrochlorothiazide decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.Minor (1)hydrochlorothiazide will increase the level or effect of aspirin by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• hydrocortisone

  Monitor Closely (1)aspirin, hydrocortisone. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of GI ulceration.Minor (1)hydrocortisone decreases levels of aspirin by increasing renal clearance. Minor/Significance Unknown.

• hydromorphone

  Monitor Closely (2)chlorpheniramine and hydromorphone both increase sedation. Use Caution/Monitor.
  
  hydromorphone increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• hydroxyzine

  Monitor Closely (2)chlorpheniramine and hydroxyzine both increase sedation. Use Caution/Monitor.
  
  hydroxyzine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• ibrutinib

  Monitor Closely (1)ibrutinib will increase the level or effect of aspirin by anticoagulation. Use Caution/Monitor. Ibrutinib may increase the risk of hemorrhage in patients receiving antiplatelet or anticoagulant therapies and monitor for signs of bleeding.

• ibuprofen

  Monitor Closely (2)aspirin and ibuprofen both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and ibuprofen both increase serum potassium. Use Caution/Monitor.Serious - Use Alternative (2)ibuprofen increases toxicity of aspirin by anticoagulation. Avoid or Use Alternate Drug. increases risk of bleeding.
  
  ibuprofen decreases effects of aspirin by Other (see comment). Avoid or Use Alternate Drug. Comment: Ibuprofen decreases the antiplatelet effects of low-dose aspirin by blocking the active site of platelet cyclooxygenase. Administer ibuprofen 8 h before aspirin or at least 2-4 h after aspirin. The effect of other NSAIDs on aspirin is not established.Minor (1)aspirin will increase the level or effect of ibuprofen by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• ibuprofen IV

  Monitor Closely (3)aspirin will increase the level or effect of ibuprofen IV by acidic (anionic) drug competition for renal tubular clearance. Modify Therapy/Monitor Closely.
  
  aspirin and ibuprofen IV both increase anticoagulation. Modify Therapy/Monitor Closely.
  
  aspirin and ibuprofen IV both increase serum potassium. Use Caution/Monitor.Serious - Use Alternative (2)ibuprofen IV increases toxicity of aspirin by anticoagulation. Avoid or Use Alternate Drug. increases risk of bleeding.
  
  ibuprofen IV decreases effects of aspirin by Other (see comment). Avoid or Use Alternate Drug. Comment: Ibuprofen decreases the antiplatelet effects of low-dose aspirin by blocking the active site of platelet cyclooxygenase. Administer ibuprofen 8 h before aspirin or at least 2-4 h after aspirin. The effect of other NSAIDs on aspirin is not established.

• icosapent

  Monitor Closely (1)icosapent, aspirin. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Icosapent may prolong bleeding time; monitor periodically if coadministered with other drugs that affect bleeding.

• idelalisib

  Serious - Use Alternative (1)idelalisib will increase the level or effect of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Idelalisib is a strong CYP3A inhibitor; avoid coadministration with sensitive CYP3A substrates

• iloperidone

  Monitor Closely (3)chlorpheniramine and iloperidone both increase sedation. Use Caution/Monitor.
  
  iloperidone increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  iloperidone increases levels of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Iloperidone is a time-dependent CYP3A inhibitor and may lead to increased plasma levels of drugs predominantly eliminated by CYP3A4.

• imatinib

  Monitor Closely (1)imatinib, aspirin. Either increases toxicity of the other by Other (see comment). Modify Therapy/Monitor Closely. Comment: Imatinib may cause thrombocytopenia; bleeding risk increased when imatinib is coadministered with anticoagulants, NSAIDs, platelet inhibitors, and thrombolytic agents.

• imidapril

  Minor (1)aspirin decreases effects of imidapril by pharmacodynamic antagonism. Minor/Significance Unknown. NSAIDs decrease prostaglandin synthesis.

• imipramine

  Monitor Closely (2)chlorpheniramine and imipramine both increase sedation. Use Caution/Monitor.
  
  imipramine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.Serious - Use Alternative (1)imipramine, phenylephrine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.

• indacaterol, inhaled

  Monitor Closely (1)phenylephrine increases effects of indacaterol, inhaled by Other (see comment). Use Caution/Monitor. Comment: If additional adrenergic drugs are to be administered by any route, they should be used with caution because the sympathetic effects of indacaterol may be potentiated.

• indapamide

  Monitor Closely (1)aspirin increases and indapamide decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.Minor (1)indapamide will increase the level or effect of aspirin by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• indomethacin

  Monitor Closely (2)aspirin and indomethacin both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and indomethacin both increase serum potassium. Use Caution/Monitor.Minor (1)aspirin will increase the level or effect of indomethacin by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• insulin aspart

  Monitor Closely (1)aspirin increases effects of insulin aspart by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Coadministration of insulin with high doses of salicylates (3 g/day or more) may increase risk for hypoglycemia. Insulin dose adjustment and increased frequency of glucose monitoring may be required.

• insulin aspart protamine/insulin aspart

  Monitor Closely (1)aspirin increases effects of insulin aspart protamine/insulin aspart by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Coadministration of insulin with high doses of salicylates (3 g/day or more) may increase risk for hypoglycemia. Insulin dose adjustment and increased frequency of glucose monitoring may be required.

• insulin degludec

  Monitor Closely (2)aspirin increases effects of insulin degludec by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Coadministration of insulin with high doses of salicylates (3 g/day or more) may increase risk for hypoglycemia. Insulin dose adjustment and increased frequency of glucose monitoring may be required.
  
  phenylephrine decreases effects of insulin degludec by pharmacodynamic antagonism. Modify Therapy/Monitor Closely. Sympathomimetics increase blood glucose by stimulating alpha and beta receptors; this action results in increased hepatic glucose production, glycogenolysis, and decreased insulin secretion.

• insulin degludec/insulin aspart

  Monitor Closely (2)phenylephrine decreases effects of insulin degludec/insulin aspart by pharmacodynamic antagonism. Modify Therapy/Monitor Closely. Sympathomimetics increase blood glucose by stimulating alpha and beta receptors; this action results in increased hepatic glucose production, glycogenolysis, and decreased insulin secretion.
  
  aspirin, insulin degludec/insulin aspart. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Both drugs decrease blood glucose.

• insulin detemir

  Monitor Closely (1)aspirin increases effects of insulin detemir by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Coadministration of insulin with high doses of salicylates (3 g/day or more) may increase risk for hypoglycemia. Insulin dose adjustment and increased frequency of glucose monitoring may be required.

• insulin glargine

  Monitor Closely (1)aspirin increases effects of insulin glargine by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Coadministration of insulin with high doses of salicylates (3 g/day or more) may increase risk for hypoglycemia. Insulin dose adjustment and increased frequency of glucose monitoring may be required.

• insulin glulisine

  Monitor Closely (1)aspirin increases effects of insulin glulisine by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Coadministration of insulin with high doses of salicylates (3 g/day or more) may increase risk for hypoglycemia. Insulin dose adjustment and increased frequency of glucose monitoring may be required.

• insulin inhaled

  Monitor Closely (2)phenylephrine decreases effects of insulin inhaled by pharmacodynamic antagonism. Modify Therapy/Monitor Closely. Sympathomimetics increase blood glucose by stimulating alpha and beta receptors; this action results in increased hepatic glucose production, glycogenolysis, and decreased insulin secretion.
  
  aspirin increases effects of insulin inhaled by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Coadministration of insulin with high doses of salicylates (3 g/day or more) may increase risk for hypoglycemia. Insulin dose adjustment and increased frequency of glucose monitoring may be required.

• insulin isophane human/insulin regular human

  Monitor Closely (1)aspirin increases effects of insulin isophane human/insulin regular human by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Coadministration of insulin with high doses of salicylates (3 g/day or more) may increase risk for hypoglycemia. Insulin dose adjustment and increased frequency of glucose monitoring may be required.

• insulin lispro

  Monitor Closely (1)aspirin increases effects of insulin lispro by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Coadministration of insulin with high doses of salicylates (3 g/day or more) may increase risk for hypoglycemia. Insulin dose adjustment and increased frequency of glucose monitoring may be required.

• insulin lispro protamine/insulin lispro

  Monitor Closely (1)aspirin increases effects of insulin lispro protamine/insulin lispro by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Coadministration of insulin with high doses of salicylates (3 g/day or more) may increase risk for hypoglycemia. Insulin dose adjustment and increased frequency of glucose monitoring may be required.

• insulin NPH

  Monitor Closely (1)aspirin increases effects of insulin NPH by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Coadministration of insulin with high doses of salicylates (3 g/day or more) may increase risk for hypoglycemia. Insulin dose adjustment and increased frequency of glucose monitoring may be required.

• insulin regular human

  Monitor Closely (1)aspirin increases effects of insulin regular human by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Coadministration of insulin with high doses of salicylates (3 g/day or more) may increase risk for hypoglycemia. Insulin dose adjustment and increased frequency of glucose monitoring may be required.

• iobenguane I 123

  Contraindicated (1)phenylephrine decreases effects of iobenguane I 123 by receptor binding competition. Contraindicated. If clinically appropriate, discontinue drugs that compete for NE receptor sites for at least 5 half-lives; may cause false-negative imaging results.

• irbesartan

  Monitor Closely (3)irbesartan, aspirin. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: May result in renal function deterioration, particularly in elderly or volume depleted individuals.
  
  aspirin decreases effects of irbesartan by pharmacodynamic antagonism. Modify Therapy/Monitor Closely. NSAIDs decrease synthesis of vasodilating renal prostaglandins, and thus affect fluid homeostasis and may diminish antihypertensive effect.
  
  irbesartan and aspirin both increase serum potassium. Use Caution/Monitor.

• isocarboxazid

  Contraindicated (1)isocarboxazid increases effects of phenylephrine by pharmacodynamic synergism. Contraindicated. Risk of acute hypertensive episode.Serious - Use Alternative (1)isocarboxazid increases effects of chlorpheniramine by Other (see comment). Avoid or Use Alternate Drug. Comment: Isocarboxazid should not be administered in combination with antihistamines because of potential additive CNS depressant effects. MAO inhibitors also prolong and intensify anticholinergic effects of antihistamines. .

• isoflurane

  Serious - Use Alternative (1)isoflurane increases toxicity of phenylephrine by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of V tach, HTN.

• isoproterenol

  Monitor Closely (4)chlorpheniramine increases and isoproterenol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  isoproterenol and phenylephrine both decrease sedation. Use Caution/Monitor.
  
  aspirin increases and isoproterenol decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  isoproterenol and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• istradefylline

  Monitor Closely (1)istradefylline will increase the level or effect of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Istradefylline 40 mg/day increased peak levels and AUC of CYP3A4 substrates in clinical trials. This effect was not observed with istradefylline 20 mg/day. Consider dose reduction of sensitive CYP3A4 substrates.

• kava

  Monitor Closely (1)kava increases effects of chlorpheniramine by pharmacodynamic synergism. Use Caution/Monitor. May enhance CNS depression.

• ketamine

  Monitor Closely (1)ketamine and chlorpheniramine both increase sedation. Use Caution/Monitor.

• ketoprofen

  Monitor Closely (2)aspirin and ketoprofen both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and ketoprofen both increase serum potassium. Use Caution/Monitor.Minor (1)aspirin will increase the level or effect of ketoprofen by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• ketorolac

  Monitor Closely (2)aspirin and ketorolac both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and ketorolac both increase serum potassium. Use Caution/Monitor.Serious - Use Alternative (1)aspirin, ketorolac. Either increases toxicity of the other by pharmacodynamic synergism. Contraindicated.Minor (1)aspirin will increase the level or effect of ketorolac by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• ketorolac intranasal

  Monitor Closely (2)aspirin and ketorolac intranasal both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and ketorolac intranasal both increase serum potassium. Use Caution/Monitor.Serious - Use Alternative (1)aspirin, ketorolac intranasal. Either increases toxicity of the other by pharmacodynamic synergism. Contraindicated.Minor (1)aspirin will increase the level or effect of ketorolac intranasal by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• ketotifen, ophthalmic

  Monitor Closely (2)chlorpheniramine and ketotifen, ophthalmic both increase sedation. Use Caution/Monitor.
  
  ketotifen, ophthalmic increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• L-methylfolate

  Minor (1)aspirin decreases levels of L-methylfolate by inhibition of GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown.

• labetalol

  Monitor Closely (2)aspirin decreases effects of labetalol by pharmacodynamic antagonism. Use Caution/Monitor. Long term (>1 wk) NSAID use. NSAIDs decrease prostaglandin synthesis.
  
  labetalol and aspirin both increase serum potassium. Use Caution/Monitor.

• lasmiditan

  Monitor Closely (1)lasmiditan, chlorpheniramine. Either increases effects of the other by sedation. Use Caution/Monitor. Coadministration of lasmiditan and other CNS depressant drugs, including alcohol have not been evaluated in clinical studies. Lasmiditan may cause sedation, as well as other cognitive and/or neuropsychiatric adverse reactions.

• latanoprost

  Monitor Closely (1)latanoprost, aspirin. unspecified interaction mechanism. Use Caution/Monitor. There are conflicting reports from studies of either increased or decreased IOP when ophthalmic prostaglandins are coadministered with NSAIDs (either systemic or ophthalmic).

• latanoprostene bunod ophthalmic

  Monitor Closely (1)latanoprostene bunod ophthalmic, aspirin. unspecified interaction mechanism. Use Caution/Monitor. There are conflicting reports from studies of either increased or decreased IOP when ophthalmic prostaglandins are coadministered with NSAIDs (either systemic or ophthalmic).

• lemborexant

  Monitor Closely (1)lemborexant, chlorpheniramine. Either increases effects of the other by sedation. Modify Therapy/Monitor Closely. Dosage adjustment may be necessary if lemborexant is coadministered with other CNS depressants because of potentially additive effects.

• lesinurad

  Serious - Use Alternative (1)aspirin decreases effects of lesinurad by unspecified interaction mechanism. Avoid or Use Alternate Drug. Aspirin at doses >325 mg/day may decrease lesinurad efficacy. Aspirin doses 325 mg/day or less (ie, for cardiovascular event prophylaxis) does not decrease lesinurad efficacy and can be coadministered.

• letermovir

  Monitor Closely (1)letermovir increases levels of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• levalbuterol

  Monitor Closely (4)aspirin increases and levalbuterol decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine increases and levalbuterol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  levalbuterol and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  levalbuterol and phenylephrine both decrease sedation. Use Caution/Monitor.

• levoketoconazole

  Minor (2)levoketoconazole will increase the level or effect of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
  
  aspirin will decrease the level or effect of levoketoconazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• levomilnacipran

  Monitor Closely (1)levomilnacipran, aspirin. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. SNRIs may further impair platelet activity in patients taking antiplatelet or anticoagulant drugs.

• levorphanol

  Monitor Closely (2)levorphanol increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and levorphanol both increase sedation. Use Caution/Monitor.

• linezolid

  Contraindicated (1)linezolid increases effects of phenylephrine by pharmacodynamic synergism. Contraindicated. Risk of acute hypertensive episode.

• lisdexamfetamine

  Monitor Closely (3)lisdexamfetamine and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  chlorpheniramine increases and lisdexamfetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  lisdexamfetamine and phenylephrine both decrease sedation. Use Caution/Monitor.

• lisinopril

  Monitor Closely (1)lisinopril, aspirin. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: May result in renal function deterioration, particularly with high dose aspirin, in elderly or volume depleted individuals.Serious - Use Alternative (1)aspirin, lisinopril. pharmacodynamic antagonism. Avoid or Use Alternate Drug. Coadministration may result in a significant decrease in renal function. NSAIDs may diminish the antihypertensive effect of ACE inhibitors. The mechanism of these interactions is likely related to the ability of NSAIDs to reduce the synthesis of vasodilating renal prostaglandins.

• lithium

  Monitor Closely (1)aspirin increases levels of lithium by decreasing renal clearance. Use Caution/Monitor.

• lofepramine

  Monitor Closely (2)chlorpheniramine and lofepramine both increase sedation. Use Caution/Monitor.
  
  lofepramine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.Serious - Use Alternative (1)lofepramine, phenylephrine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.

• lofexidine

  Monitor Closely (2)chlorpheniramine and lofexidine both increase sedation. Use Caution/Monitor.
  
  lofexidine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• lonafarnib

  Serious - Use Alternative (1)lonafarnib will increase the level or effect of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration with sensitive CYP3A substrates. If coadministration unavoidable, monitor for adverse reactions and reduce CYP3A substrate dose in accordance with product labeling.

• loprazolam

  Monitor Closely (2)loprazolam increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and loprazolam both increase sedation. Use Caution/Monitor.

• lorazepam

  Monitor Closely (2)chlorpheniramine and lorazepam both increase sedation. Use Caution/Monitor.
  
  lorazepam increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• lormetazepam

  Monitor Closely (2)chlorpheniramine and lormetazepam both increase sedation. Use Caution/Monitor.
  
  lormetazepam increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• lornoxicam

  Monitor Closely (2)aspirin and lornoxicam both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and lornoxicam both increase serum potassium. Use Caution/Monitor.Minor (1)aspirin will increase the level or effect of lornoxicam by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• losartan

  Monitor Closely (3)losartan, aspirin. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: May result in renal function deterioration, particularly in elderly or volume depleted individuals.
  
  aspirin decreases effects of losartan by pharmacodynamic antagonism. Modify Therapy/Monitor Closely. NSAIDs decrease synthesis of vasodilating renal prostaglandins, and thus affect fluid homeostasis and may diminish antihypertensive effect.
  
  losartan and aspirin both increase serum potassium. Use Caution/Monitor.

• loxapine

  Monitor Closely (2)chlorpheniramine and loxapine both increase sedation. Use Caution/Monitor.
  
  loxapine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• loxapine inhaled

  Monitor Closely (2)loxapine inhaled increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and loxapine inhaled both increase sedation. Use Caution/Monitor.

• lurasidone

  Monitor Closely (1)lurasidone, chlorpheniramine. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: Potential for increased CNS depressant effects when used concurrently; monitor for increased adverse effects and toxicity.

• macimorelin

  Serious - Use Alternative (1)aspirin, macimorelin. unspecified interaction mechanism. Avoid or Use Alternate Drug. Drugs that directly affect the pituitary secretion of growth hormone (GH) may impact the accuracy of the macimorelin diagnostic test. Allow sufficient washout time of drugs affecting GH release before administering macimorelin. .

• maprotiline

  Monitor Closely (2)maprotiline increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and maprotiline both increase sedation. Use Caution/Monitor.Serious - Use Alternative (1)maprotiline, phenylephrine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.

• marijuana

  Monitor Closely (2)chlorpheniramine and marijuana both increase sedation. Use Caution/Monitor.
  
  marijuana increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• measles, mumps, rubella and varicella vaccine, live

  Serious - Use Alternative (1)aspirin, measles, mumps, rubella and varicella vaccine, live. Mechanism: unspecified interaction mechanism. Avoid or Use Alternate Drug. Risk of Reye's Syndrome with combination; avoid salicylate use for 6 wks after vaccination.

• meclofenamate

  Monitor Closely (2)aspirin and meclofenamate both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and meclofenamate both increase serum potassium. Use Caution/Monitor.Minor (1)aspirin will increase the level or effect of meclofenamate by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• mefenamic acid

  Monitor Closely (2)aspirin and mefenamic acid both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and mefenamic acid both increase serum potassium. Use Caution/Monitor.Minor (1)aspirin will increase the level or effect of mefenamic acid by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• melatonin

  Monitor Closely (3)melatonin increases effects of aspirin by anticoagulation. Use Caution/Monitor. Melatonin may decrease prothrombin time.
  
  melatonin increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and melatonin both increase sedation. Use Caution/Monitor.

• meloxicam

  Monitor Closely (2)aspirin and meloxicam both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and meloxicam both increase serum potassium. Use Caution/Monitor.Minor (1)aspirin will increase the level or effect of meloxicam by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• meperidine

  Monitor Closely (2)chlorpheniramine and meperidine both increase sedation. Use Caution/Monitor.
  
  meperidine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• meprobamate

  Monitor Closely (2)meprobamate increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and meprobamate both increase sedation. Use Caution/Monitor.

• mesalamine

  Monitor Closely (1)mesalamine, aspirin. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Additive nephrotoxicity.Minor (1)aspirin will increase the level or effect of mesalamine by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• metaproterenol

  Monitor Closely (4)aspirin increases and metaproterenol decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  metaproterenol and phenylephrine both decrease sedation. Use Caution/Monitor.
  
  chlorpheniramine increases and metaproterenol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  metaproterenol and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• metaxalone

  Monitor Closely (1)chlorpheniramine and metaxalone both increase sedation. Use Caution/Monitor.

• methadone

  Monitor Closely (2)chlorpheniramine and methadone both increase sedation. Use Caution/Monitor.
  
  methadone increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• methamphetamine

  Monitor Closely (3)chlorpheniramine increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  methamphetamine and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  methamphetamine and phenylephrine both decrease sedation. Use Caution/Monitor.

• methazolamide

  Monitor Closely (1)methazolamide, aspirin. Either increases levels of the other by Other (see comment). Use Caution/Monitor. Comment: Carbonic anhydrase inhibitors (CAIs) and salicylates inhibit each other's renal tubular secretion, resulting in increased plasma levels. CAIs also shift salicylates from plasma to the CNS, leading to potential neurotoxicity.

• methocarbamol

  Monitor Closely (1)chlorpheniramine and methocarbamol both increase sedation. Use Caution/Monitor.

• methotrexate

  Serious - Use Alternative (1)aspirin increases levels of methotrexate by decreasing renal clearance. Avoid or Use Alternate Drug. Caution should be exercised when salicylates are given in combination with methotrexate. Risk for drug interactions with methotrexate is greatest during high-dose methotrexate therapy, it has been recommended that any of these drugs be used cautiously with methotrexate even when methotrexate is used in low doses.

• methoxyflurane

  Serious - Use Alternative (1)methoxyflurane increases toxicity of phenylephrine by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of V tach, HTN.

• methyclothiazide

  Monitor Closely (1)aspirin increases and methyclothiazide decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor. .Minor (1)methyclothiazide will increase the level or effect of aspirin by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• methyldopa

  Monitor Closely (1)methyldopa increases effects of phenylephrine by unknown mechanism. Use Caution/Monitor.

• methylenedioxymethamphetamine

  Monitor Closely (3)chlorpheniramine increases and methylenedioxymethamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  methylenedioxymethamphetamine and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  methylenedioxymethamphetamine and phenylephrine both decrease sedation. Use Caution/Monitor.

• methylergonovine

  Serious - Use Alternative (1)methylergonovine, phenylephrine. Mechanism: pharmacodynamic synergism. Contraindicated. Additive vasospasm; risk of hypertension.

• methylprednisolone

  Monitor Closely (1)aspirin, methylprednisolone. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of GI ulceration.Minor (1)methylprednisolone decreases levels of aspirin by increasing renal clearance. Minor/Significance Unknown.

• metoclopramide intranasal

  Serious - Use Alternative (1)chlorpheniramine, metoclopramide intranasal. Either increases effects of the other by Other (see comment). Avoid or Use Alternate Drug. Comment: Avoid use of metoclopramide intranasal or interacting drug, depending on importance of drug to patient.

• metolazone

  Monitor Closely (1)aspirin increases and metolazone decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.Minor (1)metolazone will increase the level or effect of aspirin by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• metoprolol

  Monitor Closely (2)aspirin decreases effects of metoprolol by pharmacodynamic antagonism. Use Caution/Monitor. Long term (>1 wk) NSAID use. NSAIDs decrease prostaglandin synthesis.
  
  metoprolol and aspirin both increase serum potassium. Use Caution/Monitor.

• midazolam

  Monitor Closely (2)midazolam increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and midazolam both increase sedation. Use Caution/Monitor.

• midazolam intranasal

  Monitor Closely (1)midazolam intranasal, chlorpheniramine. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Concomitant use of barbiturates, alcohol, or other CNS depressants may increase the risk of hypoventilation, airway obstruction, desaturation, or apnea and may contribute to profound and/or prolonged drug effect.

• midodrine

  Monitor Closely (3)midodrine and phenylephrine both decrease sedation. Use Caution/Monitor.
  
  chlorpheniramine increases and midodrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  midodrine and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• mifepristone

  Contraindicated (1)aspirin, mifepristone. Other (see comment). Contraindicated. Comment: Aspirin induced antiplatelet activity may induce excessive bleeding after an abortion w/mifepristone (RU 486).Serious - Use Alternative (1)aspirin will decrease the level or effect of mifepristone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• milnacipran

  Monitor Closely (1)milnacipran, aspirin. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of upper GI bleeding. SSRIs inhib. serotonin uptake by platelets.

• mirtazapine

  Monitor Closely (2)chlorpheniramine and mirtazapine both increase sedation. Use Caution/Monitor.
  
  mirtazapine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• mistletoe

  Monitor Closely (1)aspirin increases and mistletoe decreases anticoagulation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• mitotane

  Monitor Closely (1)mitotane decreases levels of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Mitotane is a strong inducer of cytochrome P-4503A4; monitor when coadministered with CYP3A4 substrates for possible dosage adjustments.Serious - Use Alternative (1)aspirin will decrease the level or effect of mitotane by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• modafinil

  Monitor Closely (2)chlorpheniramine increases and modafinil decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  modafinil and phenylephrine both decrease sedation. Use Caution/Monitor.

• moexipril

  Monitor Closely (1)moexipril, aspirin. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: May result in renal function deterioration, particularly with high dose aspirin, in elderly or volume depleted individuals.Serious - Use Alternative (1)aspirin, moexipril. pharmacodynamic antagonism. Avoid or Use Alternate Drug. Coadministration may result in a significant decrease in renal function. NSAIDs may diminish the antihypertensive effect of ACE inhibitors. The mechanism of these interactions is likely related to the ability of NSAIDs to reduce the synthesis of vasodilating renal prostaglandins.

• morphine

  Monitor Closely (2)chlorpheniramine and morphine both increase sedation. Use Caution/Monitor.
  
  morphine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• motherwort

  Monitor Closely (2)chlorpheniramine and motherwort both increase sedation. Use Caution/Monitor.
  
  motherwort increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• moxisylyte

  Monitor Closely (1)aspirin decreases effects of moxisylyte by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.Minor (1)moxisylyte, phenylephrine. Either decreases effects of the other by Mechanism: pharmacodynamic antagonism. Minor/Significance Unknown.

• moxonidine

  Monitor Closely (2)moxonidine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and moxonidine both increase sedation. Use Caution/Monitor.

• mycophenolate

  Monitor Closely (1)aspirin will increase the level or effect of mycophenolate by acidic (anionic) drug competition for renal tubular clearance. Use Caution/Monitor.

• nabilone

  Monitor Closely (2)chlorpheniramine and nabilone both increase sedation. Use Caution/Monitor.
  
  nabilone increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• nabumetone

  Monitor Closely (2)aspirin and nabumetone both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and nabumetone both increase serum potassium. Use Caution/Monitor.Minor (1)aspirin will increase the level or effect of nabumetone by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• nadolol

  Monitor Closely (3)nadolol and aspirin both increase serum potassium. Use Caution/Monitor.
  
  nadolol increases effects of phenylephrine by pharmacodynamic synergism. Use Caution/Monitor. Risk of acute hypertensive episode (rare).
  
  aspirin decreases effects of nadolol by pharmacodynamic antagonism. Use Caution/Monitor. Long term (>1 wk) NSAID use. NSAIDs decrease prostaglandin synthesis.

• nafcillin

  Monitor Closely (2)nafcillin, aspirin. Either increases levels of the other by plasma protein binding competition. Use Caution/Monitor.
  
  nafcillin, aspirin. Either increases levels of the other by decreasing renal clearance. Use Caution/Monitor.

• nalbuphine

  Monitor Closely (2)nalbuphine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and nalbuphine both increase sedation. Use Caution/Monitor.

• naproxen

  Monitor Closely (2)aspirin and naproxen both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and naproxen both increase serum potassium. Use Caution/Monitor.Minor (1)aspirin will increase the level or effect of naproxen by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• nebivolol

  Monitor Closely (2)aspirin decreases effects of nebivolol by pharmacodynamic antagonism. Use Caution/Monitor. Long term (>1 wk) NSAID use. NSAIDs decrease prostaglandin synthesis.
  
  nebivolol and aspirin both increase serum potassium. Use Caution/Monitor.

• nefazodone

  Monitor Closely (1)nefazodone, aspirin. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of upper GI bleeding. SSRIs inhib. serotonin uptake by platelets.

• neomycin PO

  Minor (1)aspirin increases levels of neomycin PO by decreasing renal clearance. Minor/Significance Unknown. Interaction mainly occurs in preterm infants.

• nettle

  Monitor Closely (1)aspirin increases and nettle decreases anticoagulation. Effect of interaction is not clear, use caution. Use Caution/Monitor.Minor (1)nettle increases effects of chlorpheniramine by pharmacodynamic synergism. Minor/Significance Unknown. (High dose nettle; theoretical interaction) May enhance CNS depression.

• nitazoxanide

  Monitor Closely (1)nitazoxanide, aspirin. Either increases levels of the other by Mechanism: plasma protein binding competition. Use Caution/Monitor.

• nitroglycerin rectal

  Monitor Closely (1)aspirin will increase the level or effect of nitroglycerin rectal by Other (see comment). Use Caution/Monitor. The pharmacological effects of nitroglycerin may be enhanced by concomitant administration of aspirin.

• nitroglycerin sublingual

  Monitor Closely (1)aspirin increases effects of nitroglycerin sublingual by additive vasodilation. Use Caution/Monitor. Vasodilatory and hemodynamic effects of NTG may be enhanced by coadministration with aspirin (additive effect desirable for emergent treatment).

• noni juice

  Minor (1)aspirin and noni juice both increase serum potassium. Minor/Significance Unknown.

• norepinephrine

  Monitor Closely (4)norepinephrine and phenylephrine both decrease sedation. Use Caution/Monitor.
  
  aspirin increases and norepinephrine decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  norepinephrine and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  chlorpheniramine increases and norepinephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• nortriptyline

  Monitor Closely (2)chlorpheniramine and nortriptyline both increase sedation. Use Caution/Monitor.
  
  nortriptyline increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.Serious - Use Alternative (1)nortriptyline, phenylephrine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.

• ofloxacin

  Minor (1)ofloxacin, aspirin. Other (see comment). Minor/Significance Unknown. Comment: Risk of CNS stimulation/seizure. Mechanism: Displacement of GABA from receptors in brain.

• olanzapine

  Monitor Closely (2)chlorpheniramine and olanzapine both increase sedation. Use Caution/Monitor.
  
  olanzapine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• olmesartan

  Monitor Closely (3)olmesartan, aspirin. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: May result in renal function deterioration, particularly in elderly or volume depleted individuals.
  
  aspirin decreases effects of olmesartan by pharmacodynamic antagonism. Modify Therapy/Monitor Closely. NSAIDs decrease synthesis of vasodilating renal prostaglandins, and thus affect fluid homeostasis and may diminish antihypertensive effect.
  
  olmesartan and aspirin both increase serum potassium. Use Caution/Monitor.

• olodaterol inhaled

  Monitor Closely (1)phenylephrine and olodaterol inhaled both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor. Caution with coadministration of adrenergic drugs by any route because of additive sympathetic effects

• omega 3 carboxylic acids

  Monitor Closely (1)omega 3 carboxylic acids, aspirin. Other (see comment). Use Caution/Monitor. Comment: Patients taking omega-3 acids and an anticoagulant or other drug affecting coagulation should be monitored periodically due to potential increased risk of bleeding.

• omega 3 fatty acids

  Monitor Closely (1)omega 3 fatty acids, aspirin. Other (see comment). Use Caution/Monitor. Comment: Patients taking omega-3-fatty acids and an anticoagulant or other drug affecting coagulation should be monitored periodically due to potential increased risk of bleeding. .

• opium tincture

  Monitor Closely (2)chlorpheniramine and opium tincture both increase sedation. Use Caution/Monitor.
  
  opium tincture increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• orphenadrine

  Monitor Closely (1)chlorpheniramine and orphenadrine both increase sedation. Use Caution/Monitor.

• ospemifene

  Monitor Closely (1)aspirin, ospemifene. Either increases levels of the other by plasma protein binding competition. Modify Therapy/Monitor Closely.

• oxacillin

  Monitor Closely (2)oxacillin, aspirin. Either increases levels of the other by plasma protein binding competition. Use Caution/Monitor.
  
  oxacillin, aspirin. Either increases levels of the other by decreasing renal clearance. Use Caution/Monitor.

• oxaprozin

  Monitor Closely (2)aspirin and oxaprozin both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and oxaprozin both increase serum potassium. Use Caution/Monitor.Minor (1)aspirin will increase the level or effect of oxaprozin by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• oxazepam

  Monitor Closely (2)chlorpheniramine and oxazepam both increase sedation. Use Caution/Monitor.
  
  oxazepam increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• oxycodone

  Monitor Closely (2)oxycodone increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and oxycodone both increase sedation. Use Caution/Monitor.

• oxymetazoline topical

  Monitor Closely (1)oxymetazoline topical and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• oxymorphone

  Monitor Closely (2)oxymorphone increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and oxymorphone both increase sedation. Use Caution/Monitor.

• oxytocin

  Monitor Closely (1)oxytocin increases effects of phenylephrine by pharmacodynamic synergism. Use Caution/Monitor.

• paliperidone

  Monitor Closely (2)chlorpheniramine and paliperidone both increase sedation. Use Caution/Monitor.
  
  paliperidone increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• panax ginseng

  Monitor Closely (1)aspirin and panax ginseng both increase anticoagulation. Use Caution/Monitor.

• papaveretum

  Monitor Closely (2)chlorpheniramine and papaveretum both increase sedation. Use Caution/Monitor.
  
  papaveretum increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• papaverine

  Monitor Closely (1)chlorpheniramine and papaverine both increase sedation. Use Caution/Monitor.

• parecoxib

  Monitor Closely (2)aspirin and parecoxib both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and parecoxib both increase serum potassium. Use Caution/Monitor.Minor (1)aspirin will increase the level or effect of parecoxib by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• paromomycin

  Minor (1)aspirin increases levels of paromomycin by decreasing renal clearance. Minor/Significance Unknown. Interaction mainly occurs in preterm infants.

• paroxetine

  Monitor Closely (1)paroxetine, aspirin. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of upper GI bleeding. SSRIs inhib. serotonin uptake by platelets.

• passion flower

  Monitor Closely (1)passion flower increases effects of chlorpheniramine by pharmacodynamic synergism. Use Caution/Monitor. May enhance CNS depression.

• pau d'arco

  Monitor Closely (1)aspirin and pau d'arco both increase anticoagulation. Use Caution/Monitor.

• pegaspargase

  Monitor Closely (1)pegaspargase increases effects of aspirin by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of bleeding events.

• pemetrexed

  Serious - Use Alternative (1)aspirin increases levels of pemetrexed by unspecified interaction mechanism. Avoid or Use Alternate Drug. Interrupt dosing in all patients taking NSAIDs with long elimination half-lives for at least 5d before, the day of, and 2d following pemetrexed administration. If coadministration of an NSAID is necessary, closely monitor patients for toxicity, especially myelosuppression, renal toxicity, and GI toxicity.

• penbutolol

  Monitor Closely (2)aspirin decreases effects of penbutolol by pharmacodynamic antagonism. Use Caution/Monitor. Long term (>1 wk) NSAID use. NSAIDs decrease prostaglandin synthesis.
  
  penbutolol and aspirin both increase serum potassium. Use Caution/Monitor.

• penicillin G aqueous

  Monitor Closely (2)penicillin G aqueous, aspirin. Either increases levels of the other by plasma protein binding competition. Use Caution/Monitor.
  
  penicillin G aqueous, aspirin. Either increases levels of the other by decreasing renal clearance. Use Caution/Monitor.

• penicillin VK

  Minor (1)penicillin VK, aspirin. Either increases levels of the other by decreasing renal clearance. Minor/Significance Unknown.

• pentazocine

  Monitor Closely (2)chlorpheniramine and pentazocine both increase sedation. Use Caution/Monitor.
  
  pentazocine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.Minor (1)aspirin, pentazocine. Either increases toxicity of the other by pharmacodynamic synergism. Minor/Significance Unknown. Possible risk of renal papillary necrosis w/chronic Tx.

• pentobarbital

  Monitor Closely (2)chlorpheniramine and pentobarbital both increase sedation. Use Caution/Monitor.
  
  pentobarbital increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• perindopril

  Monitor Closely (1)perindopril, aspirin. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: May result in renal function deterioration, particularly with high doses of aspirin,in elderly or volume depleted individuals.Serious - Use Alternative (1)aspirin, perindopril. pharmacodynamic antagonism. Avoid or Use Alternate Drug. Coadministration may result in a significant decrease in renal function. NSAIDs may diminish the antihypertensive effect of ACE inhibitors. The mechanism of these interactions is likely related to the ability of NSAIDs to reduce the synthesis of vasodilating renal prostaglandins.

• perphenazine

  Monitor Closely (3)perphenazine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  perphenazine, phenylephrine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.
  
  chlorpheniramine and perphenazine both increase sedation. Use Caution/Monitor.

• phendimetrazine

  Monitor Closely (3)chlorpheniramine increases and phendimetrazine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  phendimetrazine and phenylephrine both decrease sedation. Use Caution/Monitor.
  
  phendimetrazine and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• phenelzine

  Contraindicated (1)phenelzine increases effects of phenylephrine by pharmacodynamic synergism. Contraindicated. Risk of acute hypertensive episode.Monitor Closely (1)phenelzine increases effects of chlorpheniramine by Other (see comment). Modify Therapy/Monitor Closely. Comment: Coadministration of phenelzine and antihistamines may result in additive CNS depressant effects. MAO inhibitors also prolong and intensify anticholinergic effects of antihistamines. .

• phenindione

  Monitor Closely (1)phenindione and aspirin both increase anticoagulation. Modify Therapy/Monitor Closely.

• phenobarbital

  Monitor Closely (2)chlorpheniramine and phenobarbital both increase sedation. Use Caution/Monitor.
  
  phenobarbital increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• phenoxybenzamine

  Monitor Closely (1)aspirin decreases effects of phenoxybenzamine by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.Minor (1)phenoxybenzamine, phenylephrine. Either decreases effects of the other by Mechanism: pharmacodynamic antagonism. Minor/Significance Unknown.

• phentermine

  Monitor Closely (3)phentermine and phenylephrine both decrease sedation. Use Caution/Monitor.
  
  chlorpheniramine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  phentermine and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• phentolamine

  Monitor Closely (1)aspirin decreases effects of phentolamine by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.Minor (1)phentolamine, phenylephrine. Either decreases effects of the other by Mechanism: pharmacodynamic antagonism. Minor/Significance Unknown.

• phenylephrine

  Monitor Closely (1)chlorpheniramine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• phenylephrine PO

  Monitor Closely (1)chlorpheniramine increases and phenylephrine PO decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. .

• pholcodine

  Monitor Closely (2)pholcodine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and pholcodine both increase sedation. Use Caution/Monitor.

• phytoestrogens

  Monitor Closely (1)aspirin and phytoestrogens both increase anticoagulation. Use Caution/Monitor.

• pimozide

  Monitor Closely (2)chlorpheniramine and pimozide both increase sedation. Use Caution/Monitor.
  
  pimozide increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• pindolol

  Monitor Closely (3)pindolol and aspirin both increase serum potassium. Use Caution/Monitor.
  
  aspirin decreases effects of pindolol by pharmacodynamic antagonism. Use Caution/Monitor. Long term (>1 wk) NSAID use. NSAIDs decrease prostaglandin synthesis.
  
  pindolol increases effects of phenylephrine by pharmacodynamic synergism. Use Caution/Monitor. Risk of acute hypertensive episode (rare).

• piperacillin

  Minor (1)piperacillin, aspirin. Either increases effects of the other by receptor binding competition. Minor/Significance Unknown. Salicylic acid could be displaced from protein binding sites or it could itself displace other protein-bound drugs and result in an enhanced effect of the displaced drug.

• pirbuterol

  Monitor Closely (4)aspirin increases and pirbuterol decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine increases and pirbuterol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  pirbuterol and phenylephrine both decrease sedation. Use Caution/Monitor.
  
  pirbuterol and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• piroxicam

  Monitor Closely (2)aspirin and piroxicam both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and piroxicam both increase serum potassium. Use Caution/Monitor.Minor (1)aspirin will increase the level or effect of piroxicam by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• pivmecillinam

  Monitor Closely (2)pivmecillinam, aspirin. Either increases levels of the other by plasma protein binding competition. Use Caution/Monitor.
  
  pivmecillinam, aspirin. Either increases levels of the other by decreasing renal clearance. Use Caution/Monitor.

• potassium acid phosphate

  Monitor Closely (1)aspirin and potassium acid phosphate both increase serum potassium. Modify Therapy/Monitor Closely.

• potassium chloride

  Monitor Closely (1)aspirin and potassium chloride both increase serum potassium. Modify Therapy/Monitor Closely.

• potassium citrate

  Monitor Closely (1)aspirin and potassium citrate both increase serum potassium. Use Caution/Monitor.

• potassium iodide

  Monitor Closely (1)potassium iodide and aspirin both increase serum potassium. Use Caution/Monitor.

• prasugrel

  Monitor Closely (1)aspirin, prasugrel. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. The need for simultaneous use of low-dose aspirin and anticoagulant or antiplatelet agents are common for patients with cardiovascular disease; monitor closely.

• prazosin

  Monitor Closely (1)aspirin decreases effects of prazosin by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.Minor (1)prazosin, phenylephrine. Either decreases effects of the other by Mechanism: pharmacodynamic antagonism. Minor/Significance Unknown.

• prednisolone

  Monitor Closely (1)aspirin, prednisolone. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of GI ulceration.Minor (1)prednisolone decreases levels of aspirin by increasing renal clearance. Minor/Significance Unknown.

• prednisone

  Monitor Closely (1)aspirin, prednisone. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of GI ulceration.Minor (1)prednisone decreases levels of aspirin by increasing renal clearance. Minor/Significance Unknown.

• pregabalin

  Monitor Closely (1)pregabalin, chlorpheniramine. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Coadministration of CNS depressants can result in serious, life-threatening, and fatal respiratory depression. Use lowest dose possible and monitor for respiratory depression and sedation.

• primidone

  Monitor Closely (2)primidone increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and primidone both increase sedation. Use Caution/Monitor.

• probenecid

  Serious - Use Alternative (1)aspirin decreases effects of probenecid by acidic (anionic) drug competition for renal tubular clearance. Avoid or Use Alternate Drug. Aspirin decreases uricosuric action of probenecid.

• procarbazine

  Contraindicated (1)procarbazine increases effects of phenylephrine by pharmacodynamic synergism. Contraindicated. Risk of acute hypertensive episode.

• prochlorperazine

  Monitor Closely (3)chlorpheniramine and prochlorperazine both increase sedation. Use Caution/Monitor.
  
  prochlorperazine, phenylephrine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.
  
  prochlorperazine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• promazine

  Monitor Closely (1)promazine, phenylephrine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.

• promethazine

  Monitor Closely (3)promethazine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and promethazine both increase sedation. Use Caution/Monitor.
  
  promethazine, phenylephrine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.

• propofol

  Monitor Closely (2)propofol increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  propofol and chlorpheniramine both increase sedation. Use Caution/Monitor.Serious - Use Alternative (1)propofol increases levels of phenylephrine by decreasing metabolism. Contraindicated.

• propranolol

  Monitor Closely (3)propranolol and aspirin both increase serum potassium. Use Caution/Monitor.
  
  aspirin decreases effects of propranolol by pharmacodynamic antagonism. Use Caution/Monitor. Long term (>1 wk) NSAID use. NSAIDs decrease prostaglandin synthesis.
  
  propranolol increases effects of phenylephrine by pharmacodynamic synergism. Use Caution/Monitor. Risk of acute hypertensive episode (rare).

• propylhexedrine

  Monitor Closely (3)phenylephrine and propylhexedrine both decrease sedation. Use Caution/Monitor.
  
  chlorpheniramine increases and propylhexedrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  phenylephrine and propylhexedrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• protamine

  Monitor Closely (1)protamine and aspirin both increase anticoagulation. Modify Therapy/Monitor Closely.

• protriptyline

  Monitor Closely (2)chlorpheniramine and protriptyline both increase sedation. Use Caution/Monitor.
  
  protriptyline increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.Serious - Use Alternative (1)protriptyline, phenylephrine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.

• pseudoephedrine

  Monitor Closely (1)phenylephrine and pseudoephedrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• quazepam

  Monitor Closely (2)chlorpheniramine and quazepam both increase sedation. Use Caution/Monitor.
  
  quazepam increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• quetiapine

  Monitor Closely (2)quetiapine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and quetiapine both increase sedation. Use Caution/Monitor.

• quinapril

  Monitor Closely (1)quinapril, aspirin. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: May result in renal function deterioration, particularly with high doses of aspirin, in elderly or volume depleted individuals.Serious - Use Alternative (1)aspirin, quinapril. pharmacodynamic antagonism. Avoid or Use Alternate Drug. Coadministration may result in a significant decrease in renal function. NSAIDs may diminish the antihypertensive effect of ACE inhibitors. The mechanism of these interactions is likely related to the ability of NSAIDs to reduce the synthesis of vasodilating renal prostaglandins.

• ramelteon

  Monitor Closely (1)chlorpheniramine and ramelteon both increase sedation. Use Caution/Monitor.

• ramipril

  Monitor Closely (1)ramipril, aspirin. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: May result in renal function deterioration, particularly with high doses of aspirin, in elderly or volume depleted individuals.Serious - Use Alternative (1)aspirin, ramipril. pharmacodynamic antagonism. Avoid or Use Alternate Drug. Coadministration may result in a significant decrease in renal function. NSAIDs may diminish the antihypertensive effect of ACE inhibitors. The mechanism of these interactions is likely related to the ability of NSAIDs to reduce the synthesis of vasodilating renal prostaglandins.

• rasagiline

  Monitor Closely (1)rasagiline increases effects of phenylephrine by pharmacodynamic synergism. Use Caution/Monitor. Risk of acute hypertensive episode.

• reishi

  Monitor Closely (1)aspirin and reishi both increase anticoagulation. Use Caution/Monitor.

• reteplase

  Monitor Closely (1)aspirin, reteplase. Either increases toxicity of the other by anticoagulation. Use Caution/Monitor. The need for simultaneous use of low-dose aspirin and anticoagulant or antiplatelet agents are common for patients with cardiovascular disease; monitor closely.

• ribociclib

  Minor (1)ribociclib will increase the level or effect of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• risperidone

  Monitor Closely (2)chlorpheniramine and risperidone both increase sedation. Use Caution/Monitor.
  
  risperidone increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• rivaroxaban

  Monitor Closely (1)aspirin, rivaroxaban. Either increases toxicity of the other by anticoagulation. Use Caution/Monitor. Both drugs have the potential to cause bleeding. The need for simultaneous use of low-dose aspirin (<100 mg/day) with anticoagulants are common for patients with cardiovascular disease, but may result in increased bleeding; monitor closely. Promptly evaluate any signs or symptoms of blood loss if treated concomitantly with low-dose aspirin. Avoid coadministration with chronic use of higher dose aspirin.

• rivastigmine

  Monitor Closely (1)rivastigmine increases toxicity of aspirin by pharmacodynamic synergism. Use Caution/Monitor. Monitor patients for symptoms of active or occult gastrointestinal bleeding.

• rose hips

  Minor (3)rose hips will increase the level or effect of aspirin by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.
  
  aspirin decreases levels of rose hips by increasing renal clearance. Minor/Significance Unknown.
  
  rose hips increases levels of aspirin by decreasing renal clearance. Minor/Significance Unknown.

• rucaparib

  Monitor Closely (1)rucaparib will increase the level or effect of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Adjust dosage of CYP3A4 substrates, if clinically indicated.

• sacubitril/valsartan

  Monitor Closely (3)sacubitril/valsartan, aspirin. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: May result in renal function deterioration, particularly in elderly or volume depleted individuals.
  
  aspirin decreases effects of sacubitril/valsartan by pharmacodynamic antagonism. Modify Therapy/Monitor Closely. NSAIDs decrease synthesis of vasodilating renal prostaglandins, and thus affect fluid homeostasis and may diminish antihypertensive effect.
  
  sacubitril/valsartan and aspirin both increase serum potassium. Use Caution/Monitor.

• safinamide

  Monitor Closely (1)phenylephrine and safinamide both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor. Monitor patients for hypertension if safinamide is prescribed concomitantly with prescription or nonprescription sympathomimetics, including nasal, oral, or ophthalmic decongestants and cold remedies.

• sage

  Minor (2)sage increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Minor/Significance Unknown.
  
  chlorpheniramine and sage both increase sedation. Minor/Significance Unknown.

• salicylates (non-asa)

  Monitor Closely (2)aspirin and salicylates (non-asa) both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and salicylates (non-asa) both increase serum potassium. Use Caution/Monitor.Minor (1)aspirin will increase the level or effect of salicylates (non-asa) by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• salmeterol

  Monitor Closely (4)chlorpheniramine increases and salmeterol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  aspirin increases and salmeterol decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  salmeterol and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  salmeterol and phenylephrine both decrease sedation. Use Caution/Monitor.

• salsalate

  Monitor Closely (2)aspirin and salsalate both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and salsalate both increase serum potassium. Use Caution/Monitor.Minor (1)aspirin will increase the level or effect of salsalate by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• saw palmetto

  Monitor Closely (1)saw palmetto increases toxicity of aspirin by unspecified interaction mechanism. Use Caution/Monitor. May increase risk of bleeding.

• scullcap

  Monitor Closely (2)chlorpheniramine and scullcap both increase sedation. Use Caution/Monitor.
  
  scullcap increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• secobarbital

  Monitor Closely (2)secobarbital increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and secobarbital both increase sedation. Use Caution/Monitor.

• selegiline

  Monitor Closely (1)selegiline increases effects of phenylephrine by pharmacodynamic synergism. Use Caution/Monitor. Risk of acute hypertensive episode.

• selegiline transdermal

  Contraindicated (1)selegiline transdermal increases effects of phenylephrine by pharmacodynamic synergism. Contraindicated. Risk of acute hypertensive episode.

• selumetinib

  Monitor Closely (1)aspirin and selumetinib both increase anticoagulation. Modify Therapy/Monitor Closely. An increased risk of bleeding may occur in patients taking a vitamin-K antagonist or an antiplatelet agent with selumetinib. Monitor for bleeding and INR or PT in patients coadministered a vitamin-K antagonist or an antiplatelet agent with selumetinib.

• serdexmethylphenidate/dexmethylphenidate

  Monitor Closely (2)serdexmethylphenidate/dexmethylphenidate and phenylephrine both decrease sedation. Use Caution/Monitor.
  
  serdexmethylphenidate/dexmethylphenidate and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• sertraline

  Monitor Closely (1)sertraline, aspirin. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of upper GI bleeding. SSRIs inhib. serotonin uptake by platelets.

• sevoflurane

  Monitor Closely (1)sevoflurane and chlorpheniramine both increase sedation. Use Caution/Monitor.Serious - Use Alternative (2)sevoflurane increases levels of phenylephrine by decreasing metabolism. Contraindicated.
  
  sevoflurane increases toxicity of phenylephrine by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of V tach, HTN.

• shepherd's purse

  Monitor Closely (2)chlorpheniramine and shepherd's purse both increase sedation. Use Caution/Monitor.
  
  shepherd's purse increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• Siberian ginseng

  Minor (1)Siberian ginseng increases effects of chlorpheniramine by pharmacodynamic synergism. Minor/Significance Unknown. May enhance CNS depression.

• silodosin

  Monitor Closely (1)aspirin decreases effects of silodosin by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.Minor (1)silodosin, phenylephrine. Either decreases effects of the other by Mechanism: pharmacodynamic antagonism. Minor/Significance Unknown.

• sodium bicarbonate

  Minor (1)sodium bicarbonate, aspirin. Mechanism: passive renal tubular reabsorption due to increased pH. Minor/Significance Unknown. Salicylate levels increased at moderate doses; salicylate levels decreased at large doses (d/t increased renal excretion of unchanged salicylic acid).

• sodium citrate/citric acid

  Minor (1)sodium citrate/citric acid, aspirin. Mechanism: passive renal tubular reabsorption due to increased pH. Minor/Significance Unknown. Salicylate levels increased at moderate doses; salicylate levels decreased at large doses (d/t increased renal excretion of unchanged salicylic acid).

• sodium oxybate

  Serious - Use Alternative (1)chlorpheniramine, sodium oxybate. Either increases effects of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Profound sedation, respiratory depression, coma, and death may result if coadministered. Reserve concomitant prescribing of these drugs in patients for whom other treatment options are inadequate. Limit dosages and durations to the minimum required. Monitor closely for signs of respiratory depression and sedation.

• sodium picosulfate/magnesium oxide/anhydrous citric acid

  Monitor Closely (1)aspirin, sodium picosulfate/magnesium oxide/anhydrous citric acid. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: May be associated with fluid and electrolyte imbalances.

• sodium sulfate/?magnesium sulfate/potassium chloride

  Monitor Closely (1)sodium sulfate/?magnesium sulfate/potassium chloride increases toxicity of aspirin by Other (see comment). Use Caution/Monitor. Comment: Coadministration with medications that cause fluid and electrolyte abnormalities may increase the risk of adverse events of seizure, arrhythmias, and renal impairment.

• sodium sulfate/potassium sulfate/magnesium sulfate

  Monitor Closely (1)sodium sulfate/potassium sulfate/magnesium sulfate increases toxicity of aspirin by Other (see comment). Use Caution/Monitor. Comment: Coadministration with medications that cause fluid and electrolyte abnormalities may increase the risk of adverse events of seizure, arrhythmias, and renal impairment.

• solriamfetol

  Monitor Closely (1)phenylephrine and solriamfetol both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• sotalol

  Monitor Closely (2)aspirin decreases effects of sotalol by pharmacodynamic antagonism. Use Caution/Monitor. Long term (>1 wk) NSAID use. NSAIDs decrease prostaglandin synthesis.
  
  sotalol and aspirin both increase serum potassium. Use Caution/Monitor.

• spironolactone

  Monitor Closely (2)aspirin decreases effects of spironolactone by unspecified interaction mechanism. Use Caution/Monitor. When used concomitantly, spironolactone dose may need to be titrated to higher maintenance dose and the patient should be observed closely to determine if the desired effect is obtained.
  
  spironolactone and aspirin both increase serum potassium. Modify Therapy/Monitor Closely.

• stiripentol

  Monitor Closely (1)stiripentol, chlorpheniramine. affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Stiripentol is a CYP3A4 inhibitor and inducer. Monitor CYP3A4 substrates coadministered with stiripentol for increased or decreased effects. CYP3A4 substrates may require dosage adjustment.Minor (1)aspirin will decrease the level or effect of stiripentol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• streptomycin

  Minor (1)aspirin increases levels of streptomycin by decreasing renal clearance. Minor/Significance Unknown. Interaction mainly occurs in preterm infants.

• succinylcholine

  Monitor Closely (1)aspirin and succinylcholine both increase serum potassium. Use Caution/Monitor.

• sufentanil

  Monitor Closely (2)sufentanil increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and sufentanil both increase sedation. Use Caution/Monitor.

• sulfadiazine

  Minor (1)aspirin increases levels of sulfadiazine by unspecified interaction mechanism. Minor/Significance Unknown.

• sulfamethoxazole

  Monitor Closely (1)aspirin, sulfamethoxazole. Either increases effects of the other by plasma protein binding competition. Use Caution/Monitor. Due to high protein binding capacity of both drugs, one may displace the other when coadministered leading to an enhanced effect of the displaced drug; risk is low with low dose aspirin.

• sulfasalazine

  Monitor Closely (2)aspirin and sulfasalazine both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and sulfasalazine both increase serum potassium. Use Caution/Monitor.Minor (1)aspirin will increase the level or effect of sulfasalazine by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• sulfisoxazole

  Minor (1)aspirin increases levels of sulfisoxazole by unspecified interaction mechanism. Minor/Significance Unknown.

• sulindac

  Monitor Closely (2)aspirin and sulindac both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and sulindac both increase serum potassium. Use Caution/Monitor.Minor (1)aspirin will increase the level or effect of sulindac by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• tafluprost

  Monitor Closely (1)tafluprost, aspirin. unspecified interaction mechanism. Use Caution/Monitor. There are conflicting reports from studies of either increased or decreased IOP when ophthalmic prostaglandins are coadministered with NSAIDs (either systemic or ophthalmic).

• tapentadol

  Monitor Closely (2)chlorpheniramine and tapentadol both increase sedation. Use Caution/Monitor.
  
  tapentadol increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• tazemetostat

  Monitor Closely (1)tazemetostat will decrease the level or effect of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• tecovirimat

  Monitor Closely (1)tecovirimat will decrease the level or effect of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Tecovirimat is a weak CYP3A4 inducer. Monitor sensitive CYP3A4 substrates for effectiveness if coadministered.

• telmisartan

  Monitor Closely (3)telmisartan, aspirin. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: May result in renal function deterioration, particularly in elderly or volume depleted individuals.
  
  aspirin decreases effects of telmisartan by pharmacodynamic antagonism. Modify Therapy/Monitor Closely. NSAIDs decrease synthesis of vasodilating renal prostaglandins, and thus affect fluid homeostasis and may diminish antihypertensive effect.
  
  telmisartan and aspirin both increase serum potassium. Use Caution/Monitor.

• temazepam

  Monitor Closely (2)temazepam increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and temazepam both increase sedation. Use Caution/Monitor.

• temocillin

  Monitor Closely (2)temocillin, aspirin. Either increases levels of the other by plasma protein binding competition. Use Caution/Monitor.
  
  temocillin, aspirin. Either increases levels of the other by decreasing renal clearance. Use Caution/Monitor.

• tenecteplase

  Monitor Closely (1)aspirin, tenecteplase. Either increases toxicity of the other by anticoagulation. Use Caution/Monitor. The need for simultaneous use of low-dose aspirin and anticoagulant or antiplatelet agents are common for patients with cardiovascular disease; monitor closely.

• teniposide

  Minor (1)aspirin increases levels of teniposide by unspecified interaction mechanism. Minor/Significance Unknown.

• terazosin

  Monitor Closely (1)aspirin decreases effects of terazosin by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.Minor (1)terazosin, phenylephrine. Either decreases effects of the other by Mechanism: pharmacodynamic antagonism. Minor/Significance Unknown.

• terbutaline

  Monitor Closely (4)terbutaline and phenylephrine both decrease sedation. Use Caution/Monitor.
  
  terbutaline and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  chlorpheniramine increases and terbutaline decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  aspirin increases and terbutaline decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• thioridazine

  Monitor Closely (3)chlorpheniramine and thioridazine both increase sedation. Use Caution/Monitor.
  
  thioridazine, phenylephrine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.
  
  thioridazine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• thiothixene

  Monitor Closely (2)chlorpheniramine and thiothixene both increase sedation. Use Caution/Monitor.
  
  thiothixene increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• ticagrelor

  Monitor Closely (1)aspirin, ticagrelor. Other (see comment). Use Caution/Monitor. Comment: Maintenance doses of aspirin above 100 mg decreases effectiveness of ticagrelor. Therefore, after the initial loading dose of aspirin (usually 325 mg), use ticagrelor with a maintenance dose of aspirin of 75-100 mg.

• ticarcillin

  Monitor Closely (2)ticarcillin, aspirin. Either increases levels of the other by plasma protein binding competition. Use Caution/Monitor.
  
  ticarcillin, aspirin. Either increases levels of the other by decreasing renal clearance. Use Caution/Monitor.

• ticlopidine

  Serious - Use Alternative (1)aspirin increases effects of ticlopidine by pharmacodynamic synergism. Avoid or Use Alternate Drug. Enhanced risk of hemorrhage.

• tiludronate

  Minor (1)aspirin decreases levels of tiludronate by inhibition of GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown.

• timolol

  Monitor Closely (3)timolol and aspirin both increase serum potassium. Use Caution/Monitor.
  
  timolol increases effects of phenylephrine by pharmacodynamic synergism. Use Caution/Monitor. Risk of acute hypertensive episode (rare).
  
  aspirin decreases effects of timolol by pharmacodynamic antagonism. Use Caution/Monitor. Long term (>1 wk) NSAID use. NSAIDs decrease prostaglandin synthesis.

• tirofiban

  Monitor Closely (1)aspirin, tirofiban. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. The need for simultaneous use of low-dose aspirin and anticoagulant or antiplatelet agents are common for patients with cardiovascular disease; monitor closely.

• tobramycin

  Minor (1)aspirin increases levels of tobramycin by decreasing renal clearance. Minor/Significance Unknown. Interaction mainly occurs in preterm infants.

• tobramycin inhaled

  Monitor Closely (1)tobramycin inhaled and aspirin both increase nephrotoxicity and/or ototoxicity. Modify Therapy/Monitor Closely. Avoid concurrent or sequential use to decrease risk for ototoxicity

• tolazamide

  Monitor Closely (1)aspirin increases effects of tolazamide by unknown mechanism. Use Caution/Monitor. Risk of hypoglycemia.Minor (1)aspirin increases effects of tolazamide by plasma protein binding competition. Minor/Significance Unknown. Large dose of salicylate.

• tolbutamide

  Monitor Closely (1)aspirin increases effects of tolbutamide by unknown mechanism. Use Caution/Monitor. Risk of hypoglycemia.Minor (1)aspirin increases effects of tolbutamide by plasma protein binding competition. Minor/Significance Unknown. Large dose of salicylate.

• tolfenamic acid

  Monitor Closely (2)aspirin and tolfenamic acid both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and tolfenamic acid both increase serum potassium. Use Caution/Monitor.Minor (1)aspirin will increase the level or effect of tolfenamic acid by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• tolmetin

  Monitor Closely (2)aspirin and tolmetin both increase anticoagulation. Use Caution/Monitor.
  
  aspirin and tolmetin both increase serum potassium. Use Caution/Monitor.Minor (1)aspirin will increase the level or effect of tolmetin by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• tolvaptan

  Monitor Closely (1)aspirin and tolvaptan both increase serum potassium. Use Caution/Monitor.

• topiramate

  Monitor Closely (2)topiramate increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
  
  chlorpheniramine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• torsemide

  Monitor Closely (1)aspirin increases and torsemide decreases serum potassium. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• tramadol

  Monitor Closely (2)chlorpheniramine and tramadol both increase sedation. Use Caution/Monitor.
  
  tramadol increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• trandolapril

  Monitor Closely (1)trandolapril, aspirin. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: May result in renal function deterioration, particularly with high dose aspirin, in elderly and volume depleted.Serious - Use Alternative (1)aspirin, trandolapril. pharmacodynamic antagonism. Avoid or Use Alternate Drug. Coadministration may result in a significant decrease in renal function. NSAIDs may diminish the antihypertensive effect of ACE inhibitors. The mechanism of these interactions is likely related to the ability of NSAIDs to reduce the synthesis of vasodilating renal prostaglandins.

• tranylcypromine

  Contraindicated (1)tranylcypromine increases effects of phenylephrine by pharmacodynamic synergism. Contraindicated. Risk of acute hypertensive episode.Serious - Use Alternative (1)tranylcypromine increases effects of chlorpheniramine by Other (see comment). Avoid or Use Alternate Drug. Comment: Tranylcypromine should not be administered in combination with antihistamines because of potential additive CNS depressant effects. MAO inhibitors also prolong and intensify anticholinergic effects of antihistamines. .

• travoprost ophthalmic

  Monitor Closely (1)travoprost ophthalmic, aspirin. unspecified interaction mechanism. Use Caution/Monitor. There are conflicting reports from studies of either increased or decreased IOP when ophthalmic prostaglandins are coadministered with NSAIDs (either systemic or ophthalmic).

• trazodone

  Monitor Closely (3)chlorpheniramine and trazodone both increase sedation. Use Caution/Monitor.
  
  trazodone, aspirin. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of upper GI bleeding. SSRIs inhib. serotonin uptake by platelets.
  
  trazodone increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.Serious - Use Alternative (1)trazodone, phenylephrine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.

• triamcinolone acetonide injectable suspension

  Monitor Closely (1)aspirin, triamcinolone acetonide injectable suspension. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Aspirin in conjunction with corticosteroids in hypoprothrombinemia should used with caution. Clearance of salicylates may increase with concurrent use of corticosteroids.Minor (1)triamcinolone acetonide injectable suspension decreases levels of aspirin by increasing renal clearance. Minor/Significance Unknown.

• triamterene

  Monitor Closely (1)triamterene and aspirin both increase serum potassium. Modify Therapy/Monitor Closely.Minor (2)triamterene, aspirin. Other (see comment). Minor/Significance Unknown. Comment: Risk of acute renal failure. Mechanism: NSAIDs decrease prostaglandin synthesis, which normally protect against nephrotoxicity.
  
  aspirin increases toxicity of triamterene by pharmacodynamic antagonism. Minor/Significance Unknown. NSAIDs decrease prostaglandin synthesis, increasing the risk of nephrotoxicity.

• triazolam

  Monitor Closely (2)chlorpheniramine and triazolam both increase sedation. Use Caution/Monitor.
  
  triazolam increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• triclofos

  Monitor Closely (2)chlorpheniramine and triclofos both increase sedation. Use Caution/Monitor.
  
  triclofos increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• trifluoperazine

  Monitor Closely (3)chlorpheniramine and trifluoperazine both increase sedation. Use Caution/Monitor.
  
  trifluoperazine, phenylephrine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.
  
  trifluoperazine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• trimipramine

  Monitor Closely (2)trimipramine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and trimipramine both increase sedation. Use Caution/Monitor.Serious - Use Alternative (1)trimipramine, phenylephrine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.

• triprolidine

  Monitor Closely (2)triprolidine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and triprolidine both increase sedation. Use Caution/Monitor.

• tucatinib

  Serious - Use Alternative (1)tucatinib will increase the level or effect of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid concomitant use of tucatinib with CYP3A substrates, where minimal concentration changes may lead to serious or life-threatening toxicities. If unavoidable, reduce CYP3A substrate dose according to product labeling.

• valerian

  Monitor Closely (1)valerian increases effects of chlorpheniramine by pharmacodynamic synergism. Use Caution/Monitor. May enhance CNS depression.

• valganciclovir

  Minor (1)aspirin will increase the level or effect of valganciclovir by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.

• valproic acid

  Monitor Closely (1)aspirin increases levels of valproic acid by plasma protein binding competition. Use Caution/Monitor.

• valsartan

  Monitor Closely (3)valsartan, aspirin. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: May result in renal function deterioration, particularly in elderly or volume depleted individuals.
  
  aspirin decreases effects of valsartan by pharmacodynamic antagonism. Modify Therapy/Monitor Closely. NSAIDs decrease synthesis of vasodilating renal prostaglandins, and thus affect fluid homeostasis and may diminish antihypertensive effect.
  
  valsartan and aspirin both increase serum potassium. Use Caution/Monitor.

• vancomycin

  Minor (1)aspirin increases levels of vancomycin by decreasing renal clearance. Minor/Significance Unknown. Interaction mainly occurs in neonates.

• varicella virus vaccine live

  Serious - Use Alternative (1)aspirin, varicella virus vaccine live. Mechanism: unspecified interaction mechanism. Avoid or Use Alternate Drug. Risk of Reye's Syndrome with combination; avoid salicylate use for 6 wks after vaccination.

• venlafaxine

  Monitor Closely (1)venlafaxine, aspirin. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of upper GI bleeding. SSRIs inhib. serotonin uptake by platelets.

• verapamil

  Minor (1)verapamil increases effects of aspirin by unknown mechanism. Minor/Significance Unknown. Enhanced antiplatelet activity.

• voclosporin

  Monitor Closely (1)voclosporin, aspirin. Either increases toxicity of the other by nephrotoxicity and/or ototoxicity. Modify Therapy/Monitor Closely. Coadministration with drugs associated with nephrotoxicity may increase the risk for acute and/or chronic nephrotoxicity.

• vorapaxar

  Monitor Closely (2)aspirin, vorapaxar. Either increases effects of the other by anticoagulation. Use Caution/Monitor. Coadministration of anticoagulants, antiplatelets, or other drug affecting coagulation should be monitored periodically due to potential increased risk of bleeding.
  
  aspirin, vorapaxar. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Additive antiplatelet effect may occur.

• vortioxetine

  Monitor Closely (1)aspirin, vortioxetine. Either increases effects of the other by anticoagulation. Use Caution/Monitor. Risk minimal with low-dose aspirin.

• voxelotor

  Serious - Use Alternative (1)voxelotor will increase the level or effect of chlorpheniramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Voxelotor increases systemic exposure of sensitive CYP3A4 substrates. Avoid coadministration with sensitive CYP3A4 substrates with a narrow therapeutic index. Consider dose reduction of the sensitive CYP3A4 substrate(s) if unable to avoid.

• warfarin

  Monitor Closely (1)aspirin increases effects of warfarin by anticoagulation. Modify Therapy/Monitor Closely. Avoid coadministration of chronic high-dose aspirin. Aspirin's antiplatelet properties may increase anticoagulation effect of warfarin. The need for simultaneous use of low-dose aspirin and warfarin is common for patients with cardiovascular disease. .

• willow bark

  Minor (2)aspirin will increase the level or effect of willow bark by acidic (anionic) drug competition for renal tubular clearance. Minor/Significance Unknown.
  
  willow bark increases effects of aspirin by pharmacodynamic synergism. Minor/Significance Unknown. Willow bark contains salicylic acid, which may have additive effects/toxicity with salicylate drugs.

• xylometazoline

  Monitor Closely (3)chlorpheniramine increases and xylometazoline decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  phenylephrine and xylometazoline both decrease sedation. Use Caution/Monitor.
  
  phenylephrine and xylometazoline both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• yohimbe

  Serious - Use Alternative (1)yohimbe, phenylephrine. Mechanism: pharmacodynamic synergism. Contraindicated. Risk of acute hypertensive episode.

• yohimbine

  Monitor Closely (3)yohimbine and phenylephrine both decrease sedation. Use Caution/Monitor.
  
  phenylephrine and yohimbine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  chlorpheniramine increases and yohimbine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• zafirlukast

  Minor (1)aspirin increases levels of zafirlukast by unknown mechanism. Minor/Significance Unknown.

• zanubrutinib

  Monitor Closely (1)aspirin, zanubrutinib. Either increases effects of the other by anticoagulation. Modify Therapy/Monitor Closely. Zanubrutinib-induced cytopenias increases risk of hemorrhage. Coadministration of zanubritinib with antiplatelets or anticoagulants may further increase this risk.

• ziconotide

  Monitor Closely (2)chlorpheniramine and ziconotide both increase sedation. Use Caution/Monitor.
  
  ziconotide increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• ziprasidone

  Monitor Closely (2)ziprasidone increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and ziprasidone both increase sedation. Use Caution/Monitor.

• zoledronic acid

  Minor (1)aspirin decreases levels of zoledronic acid by inhibition of GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown.

• zotepine

  Monitor Closely (2)aspirin decreases effects of zotepine by pharmacodynamic antagonism. Use Caution/Monitor. NSAIDs decrease prostaglandin synthesis.
  
  chlorpheniramine and zotepine both increase sedation. Use Caution/Monitor.