Dosing & Uses
Dosage Forms & Strengths
acetaminophen/diphenhydramine/phenylephrine
caplet
- 325mg/25mg/5mg
- 325mg/12.5mg/5mg
- 650mg/25mg/10mg
liquid
- (160mg/6.25mg/2.5mg)/5mL
- (160mg/12.5mg/2.5mg)/5mL
syrup
- 325mg/12.5mg/5mg
packet
- 650mg/25mg/10mg
Rhinorrhea, Nasal Congestion, Headache
Benadryl Allergy & Cold: 2 caplet PO q4hr; not to exceed 12 capsules/day
Benadryl Allergy & Sinus Headache: 2 caplet PO q4hr; not to exceed 12 capsules/day
Benadryl Severe Allergy & Sinus Headache: 2 caplet PO q4hr; not to exceed 12 capsules/day
Robitussin Peak Cold Nighttime Multi-Symptom Cold: 20 mL PO q4hr; not to exceed 6 doses/24 hr
Sudafed PE Nighttime Cold: 2 caplet PO q4hr; not to exceed 12 caplet/day
Sudafed PE Severe Cold: 2 caplet PO q4hr; not to exceed 12 caplet/day
Theraflu Nighttime Severe Cold & Cough; 1 packet dissolved in 8 oz of water PO q4hr; not to exceed 6 packet/day
Theraflu Warming Relief Nighttime Severe Cold & Cough: 2 tablespoonfuls (30 mL) PO q4hr; not to exceed 6 doses/day
Tylenol Allergy Multi-Symptom Nighttime: 2 caplet PO q4hr; not to exceed 12 caplet/day
Dosage Forms & Strengths
acetaminophen/diphenhydramine/phenylephrine
caplet
- 325mg/25mg/5mg
- 325mg/12.5mg/5mg
- 650mg/25mg/10mg
liquid
- (160mg/6.25mg/2.5mg)/5mL
- (160mg/12.5mg/2.5mg)/5mL
syrup
- 325mg/12.5mg/5mg
packet
- 650mg/25mg/10mg
Rhinorrhea, Nasal Congestion, Headache
Benadryl Allergy & Cold
- <6 years old: Ask a pediatrician
- 6-12 years: 1 caplet PO q4hr; not to exceed 5 capsules/day
- >12 years: 2 caplet PO q4hr; not to exceed 12 capsules/day
Benadryl Allergy & Sinus Headache
- < 6 years: Ask a pediatrician
- 6-12 years: 1 capsule PO q4hr; maximum 5 capsules/day
- >12 years: 2 capsules PO q4hr; not to exceed 12 capsules/day
Benadryl Severe Allergy & Sinus Headache
- < 6 years old: Ask a pediatrician
- 6-12 years old: 1 capsule PO q4hr; maximum 5 capsules/day
- >12 years old: 2 capsules PO q4hr; not to exceed 12 capsules/day
Children's Tylenol Plus Cold & Allergy
- <4 years old: Do not use
- 4-6 years old: Ask a pediatrician
- 6-12 years old: 10 mL PO q4hr; not to exceed 5 doses/day
Robitussin Peak Cold Nighttime Multi-Symptom Cold
- <12 years: Do not use
- 12 years or older: 20 mL PO q4hr; not to exceed 6 doses/24 hr
Sudafed PE Nighttime Cold
- <12 years old: Ask a pediatrician
- >12 years old: 2 caplets PO q4hr; not to exceed 12 caplets/day
Sudafed PE Severe Cold
- <6 years: Ask a pediatrician
- 6-12 years: 1 caplets PO q4hr; not to exceed 5 caplets/day
- >12 years: 2 caplets PO q4hr; not to exceed 12 caplets/day
Theraflu Nighttime Severe Cold & Cough
- <12 years: Ask a pediatrician
- >12 years: 1 packet dissolved in 8 oz of water PO q4hr; not to exceed 6 packet/day
Theraflu Warming Relief Flu & Sore Throat
- <12 years: Ask a pediatrician
- >12 years: 2 tablespoonfuls (30 mL) PO q4hr; not to exceed 6 doses/day
Theraflu Warming Relief Nighttime Severe Cold & Cough
- <12 years: Ask a pediatrician
- >12 years: 2 tablespoonfuls (30 mL) PO q4hr; not to exceed 6 doses/day
Tylenol Allergy Multi-Symptom Nighttime
- <12 years: Do not use
- >12 years: 2 caplets PO q4hr; not to exceed 12 caplets/day
Interactions
Interaction Checker
No Results

Contraindicated
Serious - Use Alternative
Significant - Monitor Closely
Minor

Contraindicated (2)
- eliglustat
diphenhydramine increases levels of eliglustat by affecting hepatic enzyme CYP2D6 metabolism. Contraindicated. If coadministered with strong or moderate CYP2D6 inhibitors, reduce eliglustat dose from 84 mg BID to 84 mg once daily in extensive and intermediate metabolizers; eliglustat is contraindiated if strong or moderate CYP2D6 inhibitors are given concomitantly with strong or moderate CYP3A inhibitors.
- 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.
Serious - Use Alternative (33)
- 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.
- cabergoline
cabergoline, phenylephrine. Mechanism: pharmacodynamic synergism. Contraindicated. Additive vasospasm; risk of hypertension.
- calcium/magnesium/potassium/sodium oxybates
diphenhydramine, 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.
- 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
diphenhydramine, 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.
- 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.
- 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 diphenhydramine 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.
- 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
acetaminophen will increase the level or effect of lonafarnib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If coadministration of lonafarnib (a sensitive CYP3A substrate) with weak CYP3A inhibitors is unavoidable, reduce to, or continue lonafarnib at starting dose. Closely monitor for arrhythmias and events (eg, syncope, heart palpitations) since lonafarnib effect on QT interval is unknown.
- 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.
- mefloquine
mefloquine increases toxicity of diphenhydramine by QTc interval. Avoid or Use Alternate Drug. Mefloquine may enhance the QTc prolonging effect of high risk QTc prolonging agents.
- 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
diphenhydramine, 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.
- 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.
- olopatadine intranasal
diphenhydramine and olopatadine intranasal both increase sedation. Avoid or Use Alternate Drug. Coadministration increases risk of CNS depression, which can lead to additive impairment of psychomotor performance and cause daytime impairment.
- pexidartinib
acetaminophen and pexidartinib both increase Other (see comment). Avoid or Use Alternate Drug. Pexidartinib can cause hepatotoxicity. Avoid coadministration of pexidartinib with other products know to cause hepatoxicity.
- pitolisant
diphenhydramine decreases effects of pitolisant by Other (see comment). Avoid or Use Alternate Drug. Comment: Pitolisant increases histamine levels in the brain; therefore, H1 receptor antagonists that cross the blood-brain barrier may reduce the efficacy of pitolisant.
- pramlintide
pramlintide, diphenhydramine. Either increases effects of the other by pharmacodynamic synergism. Contraindicated. Synergistic inhibition of GI motility.
- pretomanid
acetaminophen, pretomanid. Either increases toxicity of the other by Other (see comment). Avoid or Use Alternate Drug. Comment: Pretomanid regimen associated with hepatotoxicity. Avoid alcohol and hepatotoxic agents, including herbal supplements and drugs other than bedaquiline and linezolid.
- propofol
propofol increases levels of phenylephrine by decreasing metabolism. Contraindicated.
Monitor Closely (355)
- aclidinium
diphenhydramine and aclidinium both decrease cholinergic effects/transmission. Use Caution/Monitor.
- acrivastine
acrivastine and diphenhydramine both increase sedation. Use Caution/Monitor.
- albuterol
albuterol and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
diphenhydramine increases and albuterol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
albuterol and phenylephrine both decrease sedation. Use Caution/Monitor. - alfentanil
alfentanil increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
diphenhydramine and alfentanil both increase sedation. Use Caution/Monitor. - alprazolam
alprazolam increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
diphenhydramine and alprazolam both increase sedation. Use Caution/Monitor. - amantadine
diphenhydramine, amantadine. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Potential for increased anticholinergic adverse effects.
- amitriptyline
amitriptyline increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- amifampridine
diphenhydramine 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.
- amisulpride
amisulpride and diphenhydramine both increase sedation. Use Caution/Monitor.
- amitriptyline
diphenhydramine and amitriptyline both decrease cholinergic effects/transmission. Modify Therapy/Monitor Closely.
diphenhydramine 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.
diphenhydramine 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.
diphenhydramine and amoxapine both decrease cholinergic effects/transmission. Use Caution/Monitor.
diphenhydramine and amoxapine both increase sedation. Use Caution/Monitor. - anticholinergic/sedative combos
anticholinergic/sedative combos and diphenhydramine both decrease cholinergic effects/transmission. Use Caution/Monitor.
- apalutamide
apalutamide will decrease the level or effect of acetaminophen by increasing elimination. Use Caution/Monitor. Apalutamide induces UGT and may decrease systemic exposure of drugs that are UGT substrates.
- 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. - apomorphine
diphenhydramine and apomorphine both increase sedation. Use Caution/Monitor.
- arformoterol
diphenhydramine increases and arformoterol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- aripiprazole
aripiprazole increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
aripiprazole increases effects of diphenhydramine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.
diphenhydramine decreases levels of aripiprazole by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
diphenhydramine and aripiprazole both increase sedation. Use Caution/Monitor.
diphenhydramine decreases levels of aripiprazole by pharmacodynamic antagonism. Use Caution/Monitor. - armodafinil
armodafinil and phenylephrine both decrease sedation. Use Caution/Monitor.
diphenhydramine increases and armodafinil decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - asenapine
asenapine and diphenhydramine both increase sedation. Use Caution/Monitor.
- atogepant
acetaminophen will increase the level or effect of atogepant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- 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.
- asenapine transdermal
asenapine transdermal and diphenhydramine both increase sedation. Use Caution/Monitor.
- atomoxetine
diphenhydramine will increase the level or effect of atomoxetine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
- atracurium
atracurium and diphenhydramine both decrease cholinergic effects/transmission. Use Caution/Monitor.
- atropine
atropine and diphenhydramine both decrease cholinergic effects/transmission. Use Caution/Monitor.
- atropine IV/IM
atropine IV/IM and diphenhydramine both decrease cholinergic effects/transmission. Use Caution/Monitor.
- avapritinib
acetaminophen will increase the level or effect of avapritinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
avapritinib and diphenhydramine both increase sedation. Use Caution/Monitor. - axitinib
acetaminophen increases levels of axitinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- azelastine
azelastine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
azelastine and diphenhydramine both increase sedation. Use Caution/Monitor. - baclofen
diphenhydramine and baclofen both increase sedation. Use Caution/Monitor.
- belladonna and opium
belladonna and opium increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- belladonna alkaloids
belladonna alkaloids and diphenhydramine both decrease cholinergic effects/transmission. Use Caution/Monitor.
- belladonna and opium
diphenhydramine and belladonna and opium both decrease cholinergic effects/transmission. Use Caution/Monitor.
diphenhydramine and belladonna and opium both increase sedation. Use Caution/Monitor. - benperidol
benperidol increases effects of diphenhydramine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.
diphenhydramine decreases levels of benperidol by pharmacodynamic antagonism. Use Caution/Monitor.
benperidol increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
diphenhydramine and benperidol both increase sedation. Use Caution/Monitor.
diphenhydramine decreases levels of benperidol by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. - benzhydrocodone/acetaminophen
diphenhydramine will increase the level or effect of benzhydrocodone/acetaminophen by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Hydromorphone (<3% of the circulating parent hydrocodone [benzhydrocodone is prodrug of hydrocodone]) is mainly formed by CYP2D6 mediated O-demethylation of hydrocodone. Hydromorphone may contribute to the total analgesic effect of hydrocodone.
benzhydrocodone/acetaminophen and diphenhydramine both increase sedation. Use Caution/Monitor. - benzphetamine
benzphetamine and phenylephrine both decrease sedation. Use Caution/Monitor.
benzphetamine and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor. - benzphetamine
diphenhydramine increases and benzphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- benztropine
benztropine and diphenhydramine both decrease cholinergic effects/transmission. Use Caution/Monitor. Additive anticholinergic adverse effects may be seen with concurrent use.
- bethanechol
bethanechol increases and diphenhydramine decreases cholinergic effects/transmission. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- brexanolone
brexanolone, diphenhydramine. Either increases toxicity of the other by sedation. Use Caution/Monitor.
- brexpiprazole
diphenhydramine will increase the level or effect of brexpiprazole by affecting hepatic enzyme CYP2D6 metabolism. Modify Therapy/Monitor Closely. Administer a quarter of brexpiprazole dose if coadministered with a moderate CYP2D6 inhibitor PLUS a strong/moderate CYP3A4 inhibitor.
brexpiprazole and diphenhydramine both increase sedation. Use Caution/Monitor. - brimonidine
brimonidine and diphenhydramine both increase sedation. Use Caution/Monitor.
- brivaracetam
brivaracetam and diphenhydramine both increase sedation. Use Caution/Monitor.
- bromocriptine
bromocriptine, phenylephrine. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Hypertension, V tach.
- brompheniramine
brompheniramine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
brompheniramine and diphenhydramine both increase sedation. Use Caution/Monitor. - bupivacaine implant
acetaminophen, bupivacaine implant. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: Local anesthetics may increase the risk of developing methemoglobinemia when concurrently exposed to drugs that also cause methemoglobinemia.
- buprenorphine
diphenhydramine and buprenorphine both increase sedation. Use Caution/Monitor.
- buprenorphine buccal
buprenorphine buccal increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- buprenorphine buccal
diphenhydramine and buprenorphine buccal both increase sedation. Use Caution/Monitor.
- buprenorphine subdermal implant
buprenorphine subdermal implant and diphenhydramine both increase sedation. Use Caution/Monitor.
- buprenorphine transdermal
buprenorphine transdermal and diphenhydramine both increase sedation. Use Caution/Monitor.
- buprenorphine, long-acting injection
buprenorphine, long-acting injection and diphenhydramine both increase sedation. Use Caution/Monitor.
- busulfan
acetaminophen increases levels of busulfan by decreasing metabolism. Use Caution/Monitor. Use of acetaminophen prior to (< 72 hours) or concurrently with busulfan may result in decreased clearance of busulfan due to acetaminophen-induced decreases in glutathione levels.
- butabarbital
butabarbital increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
diphenhydramine and butabarbital both increase sedation. Use Caution/Monitor. - butalbital
diphenhydramine 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
butorphanol increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
diphenhydramine and butorphanol both increase sedation. Use Caution/Monitor. - caffeine
diphenhydramine 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. - carbachol
carbachol increases and diphenhydramine decreases cholinergic effects/transmission. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- carbinoxamine
carbinoxamine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- carbinoxamine
carbinoxamine and diphenhydramine both increase sedation. Use Caution/Monitor.
- carisoprodol
diphenhydramine and carisoprodol both increase sedation. Use Caution/Monitor.
- carvedilol
diphenhydramine will increase the level or effect of carvedilol by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
- cenobamate
cenobamate, diphenhydramine. Either increases effects of the other by sedation. Use Caution/Monitor.
- cevimeline
cevimeline increases and diphenhydramine decreases cholinergic effects/transmission. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- chloral hydrate
diphenhydramine 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
diphenhydramine 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. - chlorpheniramine
chlorpheniramine 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. - chlorpromazine
diphenhydramine and chlorpromazine both increase sedation. Use Caution/Monitor.
diphenhydramine decreases levels of chlorpromazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
diphenhydramine decreases levels of chlorpromazine by pharmacodynamic antagonism. Use Caution/Monitor.
chlorpromazine increases effects of diphenhydramine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.
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. - chlorzoxazone
diphenhydramine and chlorzoxazone both increase sedation. Use Caution/Monitor.
- cinnarizine
cinnarizine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- cinnarizine
cinnarizine and diphenhydramine both increase sedation. Use Caution/Monitor.
- cisatracurium
cisatracurium and diphenhydramine both decrease cholinergic effects/transmission. Use Caution/Monitor.
- clemastine
clemastine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
clemastine and diphenhydramine both increase sedation. Use Caution/Monitor. - clobazam
diphenhydramine, 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
diphenhydramine will increase the level or effect of clomipramine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
diphenhydramine and clomipramine both decrease cholinergic effects/transmission. Use Caution/Monitor.
diphenhydramine 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.
diphenhydramine and clonazepam both increase sedation. Use Caution/Monitor. - clorazepate
diphenhydramine 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
clozapine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
diphenhydramine decreases levels of clozapine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
diphenhydramine and clozapine both increase sedation. Use Caution/Monitor.
diphenhydramine decreases levels of clozapine by pharmacodynamic antagonism. Use Caution/Monitor.
clozapine increases effects of diphenhydramine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia. - codeine
diphenhydramine decreases effects of codeine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Prevents conversion of codeine to its active metabolite morphine.
diphenhydramine 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. - cyclizine
cyclizine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
cyclizine and diphenhydramine both increase sedation. Use Caution/Monitor.
cyclizine and diphenhydramine both decrease cholinergic effects/transmission. Use Caution/Monitor. - cyclobenzaprine
cyclobenzaprine and diphenhydramine both decrease cholinergic effects/transmission. Use Caution/Monitor.
diphenhydramine and cyclobenzaprine both increase sedation. Use Caution/Monitor. - cyproheptadine
cyproheptadine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- cyproheptadine
cyproheptadine and diphenhydramine both increase sedation. Use Caution/Monitor.
- dantrolene
diphenhydramine and dantrolene both increase sedation. Use Caution/Monitor.
- dapsone topical
acetaminophen increases toxicity of dapsone topical by altering metabolism. Modify Therapy/Monitor Closely. May induce methemoglobinemia .
- daridorexant
diphenhydramine 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.
- darifenacin
darifenacin and diphenhydramine both decrease cholinergic effects/transmission. Use Caution/Monitor.
- desflurane
desflurane and diphenhydramine both increase sedation. Use Caution/Monitor.
- desipramine
diphenhydramine will increase the level or effect of desipramine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
diphenhydramine 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. - deutetrabenazine
diphenhydramine and deutetrabenazine both increase sedation. Use Caution/Monitor.
- dexchlorpheniramine
dexchlorpheniramine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- dexchlorpheniramine
dexchlorpheniramine and diphenhydramine both increase sedation. Use Caution/Monitor.
- dexfenfluramine
diphenhydramine 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.
diphenhydramine and dexmedetomidine both increase sedation. Use Caution/Monitor. - dexmethylphenidate
dexmethylphenidate and phenylephrine both decrease sedation. Use Caution/Monitor.
diphenhydramine 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.
diphenhydramine 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
diphenhydramine 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
diphenhydramine 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
diphenhydramine 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, diphenhydramine. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Coadministration may potentiate the CNS-depressant effects of each drug.
- dicyclomine
dicyclomine and diphenhydramine both decrease cholinergic effects/transmission. Use Caution/Monitor.
- diethylpropion
diphenhydramine increases and diethylpropion decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- difelikefalin
difelikefalin and diphenhydramine 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.
diphenhydramine and difenoxin hcl both increase sedation. Use Caution/Monitor. - dimenhydrinate
dimenhydrinate increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
dimenhydrinate and diphenhydramine both increase sedation. Use Caution/Monitor. - diphenhydramine
diphenhydramine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- diphenoxylate hcl
diphenhydramine and diphenoxylate hcl both increase sedation. Use Caution/Monitor.
- diphenoxylate hcl
diphenoxylate hcl increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- dipipanone
diphenhydramine 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. - dobutamine
dobutamine and phenylephrine both decrease sedation. Use Caution/Monitor.
diphenhydramine increases and dobutamine decreases sedation. 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
donepezil increases and diphenhydramine decreases cholinergic effects/transmission. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- dopamine
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. - donepezil transdermal
donepezil transdermal, diphenhydramine. Either decreases effects of the other by pharmacodynamic antagonism. Use Caution/Monitor.
- dopamine
diphenhydramine increases and dopamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- dopexamine
dopexamine and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
diphenhydramine increases and dopexamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
dopexamine and phenylephrine both decrease sedation. Use Caution/Monitor. - dosulepin
diphenhydramine and dosulepin both decrease cholinergic effects/transmission. Use Caution/Monitor.
diphenhydramine 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.
- doxepin
diphenhydramine and doxepin both decrease cholinergic effects/transmission. Use Caution/Monitor.
diphenhydramine and doxepin both increase sedation. Use Caution/Monitor. - doxylamine
diphenhydramine and doxylamine both increase sedation. Use Caution/Monitor.
- droperidol
diphenhydramine decreases levels of droperidol by pharmacodynamic antagonism. Use Caution/Monitor.
droperidol increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
diphenhydramine and droperidol both increase sedation. Use Caution/Monitor.
diphenhydramine decreases levels of droperidol by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
droperidol increases effects of diphenhydramine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia. - 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
diphenhydramine will increase the level or effect of duloxetine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
- echothiophate iodide
echothiophate iodide increases and diphenhydramine decreases cholinergic effects/transmission. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- eltrombopag
eltrombopag increases levels of acetaminophen by decreasing metabolism. Use Caution/Monitor. UGT inhibition; significance of interaction unclear.
- ephedrine
ephedrine, phenylephrine. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor.
ephedrine and phenylephrine both decrease sedation. Use Caution/Monitor.
diphenhydramine 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
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.
diphenhydramine 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
diphenhydramine increases and epinephrine racemic decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- epinephrine racemic
epinephrine racemic and phenylephrine both decrease sedation. Use Caution/Monitor.
epinephrine racemic and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor. - esketamine intranasal
esketamine intranasal, diphenhydramine. Either increases toxicity of the other by sedation. Modify Therapy/Monitor Closely.
- estazolam
estazolam increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
diphenhydramine and estazolam both increase sedation. Use Caution/Monitor. - ethanol
ethanol increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
diphenhydramine and ethanol both increase sedation. Use Caution/Monitor. - etomidate
etomidate and diphenhydramine both increase sedation. Use Caution/Monitor.
- exenatide injectable solution
exenatide injectable solution will decrease the level or effect of acetaminophen by unspecified interaction mechanism. Use Caution/Monitor. To avoid potential interaction, give acetaminophen at least 1 hour before or 4 hours after exenatide injection.
- exenatide injectable suspension
exenatide injectable suspension will decrease the level or effect of acetaminophen by unspecified interaction mechanism. Use Caution/Monitor. To avoid potential interaction, give acetaminophen at least 1 hour before or 4 hours after exenatide injection.
- 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. - fenfluramine
diphenhydramine increases and fenfluramine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- fentanyl
fentanyl, diphenhydramine. 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 and diphenhydramine both increase sedation. Use Caution/Monitor. - fentanyl intranasal
fentanyl intranasal, diphenhydramine. 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 and diphenhydramine both increase sedation. Use Caution/Monitor. - fentanyl iontophoretic transdermal system
fentanyl iontophoretic transdermal system and diphenhydramine both increase sedation. Use Caution/Monitor.
- fentanyl transdermal
fentanyl transdermal, diphenhydramine. 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 and diphenhydramine both increase sedation. Use Caution/Monitor. - fentanyl transmucosal
fentanyl transmucosal, diphenhydramine. 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.
- fesoterodine
diphenhydramine and fesoterodine both decrease cholinergic effects/transmission. Use Caution/Monitor.
- finerenone
acetaminophen will increase the level or effect of finerenone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Monitor serum potassium during initiation and dosage adjustment of either finererone or moderate CYP3A4 inhibitors. Adjust finererone dosage as needed.
- flavoxate
diphenhydramine and flavoxate both decrease cholinergic effects/transmission. Use Caution/Monitor.
- flecainide
diphenhydramine will increase the level or effect of flecainide by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
- flibanserin
diphenhydramine and flibanserin both increase sedation. Modify Therapy/Monitor Closely. Risk for sedation increased if flibanserin is coadministration with other CNS depressants.
acetaminophen will increase the level or effect of flibanserin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Increased flibanserin adverse effects may occur if coadministered with multiple weak CYP3A4 inhibitors. - fluphenazine
fluphenazine increases effects of diphenhydramine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.
diphenhydramine decreases levels of fluphenazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
fluphenazine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
diphenhydramine 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.
diphenhydramine decreases levels of fluphenazine by pharmacodynamic antagonism. Use Caution/Monitor. - imatinib
imatinib decreases levels of acetaminophen by decreasing hepatic clearance. Modify Therapy/Monitor Closely. In vitro, imatinib was found to inhibit acetaminophen O-glucuronidation (Ki value of 58.5 micro-M) at therapeutic levels; avoid chronic acetaminophen therapy with imatinib; if occasional acetaminophen administered, do not exceed 1300 mg/day.
- flurazepam
diphenhydramine 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. - formoterol
diphenhydramine increases and formoterol decreases sedation. 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. - gabapentin
gabapentin, diphenhydramine. 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.
- haloperidol
haloperidol increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- gabapentin enacarbil
gabapentin enacarbil, diphenhydramine. 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.
- galantamine
galantamine increases and diphenhydramine decreases cholinergic effects/transmission. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- ganaxolone
diphenhydramine and ganaxolone both increase sedation. Use Caution/Monitor.
- glycopyrrolate
diphenhydramine and glycopyrrolate both decrease cholinergic effects/transmission. Use Caution/Monitor.
- glycopyrrolate inhaled
diphenhydramine and glycopyrrolate inhaled both decrease cholinergic effects/transmission. Use Caution/Monitor.
- glycopyrronium tosylate topical
glycopyrronium tosylate topical, diphenhydramine. 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 diphenhydramine by pharmacodynamic synergism. Use Caution/Monitor. May enhance CNS depression.
- haloperidol
diphenhydramine will increase the level or effect of haloperidol by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
diphenhydramine and haloperidol both increase sedation. Use Caution/Monitor.
diphenhydramine decreases levels of haloperidol by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
diphenhydramine decreases levels of haloperidol by pharmacodynamic antagonism. Use Caution/Monitor.
haloperidol increases effects of diphenhydramine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia. - hawthorn
hawthorn increases effects of diphenhydramine by pharmacodynamic synergism. Use Caution/Monitor. May enhance CNS depression.
- henbane
diphenhydramine and henbane both decrease cholinergic effects/transmission. Use Caution/Monitor.
- homatropine
diphenhydramine and homatropine both decrease cholinergic effects/transmission. Use Caution/Monitor.
- hops
hops increases effects of diphenhydramine by pharmacodynamic synergism. Use Caution/Monitor. May enhance CNS depression.
- huperzine A
huperzine A increases and diphenhydramine decreases cholinergic effects/transmission. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- hyaluronidase
diphenhydramine 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.
- hydralazine
hydralazine, phenylephrine. Mechanism: pharmacodynamic antagonism. Use Caution/Monitor. Sympathomimetics can antagonize the activity of some antihypertensive agents.
- hydrocodone
diphenhydramine will increase the level or effect of hydrocodone by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Hydromorphone (<3% of the circulating parent hydrocodone) is mainly formed by CYP2D6 mediated O-demethylation of hydrocodone. Hydromorphone may contribute to the total analgesic effect of hydrocodone.
- hydromorphone
diphenhydramine will increase the level or effect of hydromorphone by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
diphenhydramine 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
diphenhydramine 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. - hyoscyamine
diphenhydramine and hyoscyamine both decrease cholinergic effects/transmission. Use Caution/Monitor.
- iloperidone
iloperidone increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- hyoscyamine spray
diphenhydramine and hyoscyamine spray both decrease cholinergic effects/transmission. Use Caution/Monitor.
- iloperidone
diphenhydramine will increase the level or effect of iloperidone by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
diphenhydramine and iloperidone both increase sedation. Use Caution/Monitor.
diphenhydramine decreases levels of iloperidone by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
diphenhydramine decreases levels of iloperidone by pharmacodynamic antagonism. Use Caution/Monitor.
iloperidone increases effects of diphenhydramine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia. - imipramine
imipramine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
diphenhydramine and imipramine both decrease cholinergic effects/transmission. Use Caution/Monitor.
diphenhydramine and imipramine both increase sedation. Use Caution/Monitor.
diphenhydramine will increase the level or effect of imipramine by affecting hepatic enzyme CYP2D6 metabolism. 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.
- ipratropium
diphenhydramine and ipratropium both decrease cholinergic effects/transmission. Use Caution/Monitor. Due to the poor systemic absorption of ipratropium, interaction unlikely at regularly recommended dosages.
- insulin degludec
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.
- 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.
- isavuconazonium sulfate
acetaminophen will increase the level or effect of isavuconazonium sulfate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- isoniazid
isoniazid will increase the level or effect of acetaminophen by affecting hepatic enzyme CYP2E1 metabolism. Use Caution/Monitor.
- isoproterenol
isoproterenol and phenylephrine both decrease sedation. Use Caution/Monitor.
diphenhydramine increases and isoproterenol decreases sedation. 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. - ivacaftor
acetaminophen increases levels of ivacaftor by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Monitor when coadministered with weak CYP3A4 inhibitors .
- kava
kava increases effects of diphenhydramine by pharmacodynamic synergism. Use Caution/Monitor. May enhance CNS depression.
- ketotifen, ophthalmic
ketotifen, ophthalmic increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- ketamine
ketamine and diphenhydramine both increase sedation. Use Caution/Monitor.
- ketotifen, ophthalmic
diphenhydramine and ketotifen, ophthalmic both increase sedation. Use Caution/Monitor.
- lasmiditan
lasmiditan, diphenhydramine. 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.
- lemborexant
acetaminophen will increase the level or effect of lemborexant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Lower nightly dose of lemborexant recommended if coadministered with weak CYP3A4 inhibitors. See drug monograph for specific dosage modification.
lemborexant, diphenhydramine. 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. - levalbuterol
levalbuterol and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
diphenhydramine 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. - levonorgestrel oral/ethinylestradiol/ferrous bisglycinate
levonorgestrel oral/ethinylestradiol/ferrous bisglycinate will decrease the level or effect of acetaminophen by unknown mechanism. Use Caution/Monitor.
acetaminophen increases levels of levonorgestrel oral/ethinylestradiol/ferrous bisglycinate by decreasing hepatic clearance. Use Caution/Monitor. Coadministration of ascorbic acid and certain combined hormonal contraceptives (CHCs) containing EE may increase plasma EE concentrations, possibly by inhibition of conjugation. - levodopa
diphenhydramine, levodopa. Other (see comment). Use Caution/Monitor. Comment: Anticholinergic agents may enhance the therapeutic effects of levodopa; however, anticholinergic agents can exacerbate tardive dyskinesia. In high dosage, anticholinergics may decrease the effects of levodopa by delaying its GI absorption. .
- levorphanol
levorphanol increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- levorphanol
diphenhydramine 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.
diphenhydramine increases and lisdexamfetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - lixisenatide (DSC)
lixisenatide (DSC) will decrease the level or effect of acetaminophen by inhibition of GI absorption. Applies only to oral form of both agents. Modify Therapy/Monitor Closely. GLP1 agonists delay gastric emptying, which may affect absorption of concomitantly administered oral medications. No effects on acetaminophen Cmax and Tmax were observed when acetaminophen was administered 1 hr before lixisenatide. When administered 1 or 4 hr after lixisenatide, acetaminophen Cmax was decreased by 29% and 31% respectively and median Tmax was delayed by 2 and 1.75 hr, respectively.
- lofepramine
diphenhydramine will increase the level or effect of lofepramine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
diphenhydramine and lofepramine both decrease cholinergic effects/transmission. Use Caution/Monitor.
diphenhydramine 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. - lofexidine
lofexidine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
diphenhydramine and lofexidine both increase sedation. Use Caution/Monitor. - lomitapide
acetaminophen increases levels of lomitapide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Lomitapide dose should not exceed 30 mg/day.
- loprazolam
loprazolam increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
diphenhydramine and loprazolam both increase sedation. Use Caution/Monitor. - lorazepam
lorazepam increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
diphenhydramine and lorazepam both increase sedation. Use Caution/Monitor. - lormetazepam
diphenhydramine 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. - loxapine
diphenhydramine and loxapine both increase sedation. Use Caution/Monitor.
diphenhydramine decreases levels of loxapine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
diphenhydramine decreases levels of loxapine by pharmacodynamic antagonism. Use Caution/Monitor.
loxapine increases effects of diphenhydramine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.
loxapine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - loxapine inhaled
diphenhydramine and loxapine inhaled both increase sedation. Use Caution/Monitor.
loxapine inhaled increases effects of diphenhydramine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.
loxapine inhaled increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
diphenhydramine decreases levels of loxapine inhaled by pharmacodynamic antagonism. Use Caution/Monitor. - lurasidone
lurasidone, diphenhydramine. 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
diphenhydramine and maprotiline both decrease cholinergic effects/transmission. Use Caution/Monitor.
diphenhydramine and maprotiline both increase sedation. Use Caution/Monitor. - marijuana
diphenhydramine 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. - meclizine
diphenhydramine and meclizine both decrease cholinergic effects/transmission. Use Caution/Monitor.
- melatonin
melatonin increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- melatonin
diphenhydramine and melatonin both increase sedation. Use Caution/Monitor.
- meperidine
meperidine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
diphenhydramine 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.
diphenhydramine and meprobamate both increase sedation. Use Caution/Monitor. - metaproterenol
metaproterenol and phenylephrine both decrease sedation. Use Caution/Monitor.
diphenhydramine 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
diphenhydramine 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.
- methadone
diphenhydramine and methadone both increase sedation. Use Caution/Monitor.
- methamphetamine
methamphetamine and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
diphenhydramine increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
diphenhydramine will increase the level or effect of methamphetamine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
methamphetamine and phenylephrine both decrease sedation. Use Caution/Monitor. - methocarbamol
diphenhydramine and methocarbamol both increase sedation. Use Caution/Monitor.
- methyldopa
methyldopa increases effects of phenylephrine by unknown mechanism. Use Caution/Monitor.
- methscopolamine
diphenhydramine and methscopolamine both decrease cholinergic effects/transmission. Use Caution/Monitor.
- methylenedioxymethamphetamine
diphenhydramine 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. - metoprolol
diphenhydramine will increase the level or effect of metoprolol by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
- midazolam
midazolam increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- mexiletine
diphenhydramine will increase the level or effect of mexiletine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
- midazolam
diphenhydramine and midazolam both increase sedation. Use Caution/Monitor.
- midazolam intranasal
midazolam intranasal, diphenhydramine. Either increases toxicity of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Concomitant use of barbiturates, alcohol, or other CNS depressants may increase risk of hypoventilation, airway obstruction, desaturation, or apnea and may contribute to profound and/or prolonged drug effect.
acetaminophen will increase the level or effect of midazolam intranasal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Coadministration of mild CYP3A4 inhibitors with midazolam intranasal may cause higher midazolam systemic exposure, which may prolong sedation. - midodrine
midodrine and phenylephrine both decrease sedation. Use Caution/Monitor.
diphenhydramine 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. - mipomersen
mipomersen, acetaminophen. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: Both drugs have potential to increase hepatic enzymes; monitor LFTs.
- mirtazapine
diphenhydramine 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. - modafinil
modafinil and phenylephrine both decrease sedation. Use Caution/Monitor.
diphenhydramine increases and modafinil decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - morphine
diphenhydramine and morphine both increase sedation. Use Caution/Monitor.
diphenhydramine will increase the level or effect of morphine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
morphine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - motherwort
diphenhydramine 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. - moxonidine
moxonidine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
diphenhydramine and moxonidine both increase sedation. Use Caution/Monitor. - nabilone
nabilone increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
diphenhydramine and nabilone both increase sedation. Use Caution/Monitor. - nadolol
nadolol increases effects of phenylephrine by pharmacodynamic synergism. Use Caution/Monitor. Risk of acute hypertensive episode (rare).
- nalbuphine
diphenhydramine and nalbuphine both increase sedation. Use Caution/Monitor.
- nalbuphine
nalbuphine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- nebivolol
diphenhydramine will increase the level or effect of nebivolol by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
- neostigmine
neostigmine increases and diphenhydramine decreases cholinergic effects/transmission. Effect of interaction is not clear, use caution. 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.
diphenhydramine 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.
diphenhydramine and nortriptyline both decrease cholinergic effects/transmission. Use Caution/Monitor.
diphenhydramine and nortriptyline both increase sedation. Use Caution/Monitor.
diphenhydramine will increase the level or effect of nortriptyline by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. - olanzapine
diphenhydramine decreases levels of olanzapine by pharmacodynamic antagonism. Use Caution/Monitor.
olanzapine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
diphenhydramine and olanzapine both increase sedation. Use Caution/Monitor.
diphenhydramine decreases levels of olanzapine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
olanzapine increases effects of diphenhydramine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia. - oliceridine
diphenhydramine will increase the level or effect of oliceridine by affecting hepatic enzyme CYP2D6 metabolism. Modify Therapy/Monitor Closely. If concomitant use is necessary, may require less frequent oliceridine dosing. Closely monitor for respiratory depression and sedation and titrate subsequent doses accordingly. If inhibitor is discontinued, consider increase oliceridine dosage until stable drug effects are achieved. Monitor for signs of opioid withdrawal.
- 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
- onabotulinumtoxinA
onabotulinumtoxinA and diphenhydramine both decrease cholinergic effects/transmission. Use Caution/Monitor.
- opium tincture
diphenhydramine 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
diphenhydramine and orphenadrine both decrease cholinergic effects/transmission. Use Caution/Monitor.
diphenhydramine 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
diphenhydramine, ospemifene. Either increases levels of the other by plasma protein binding competition. Modify Therapy/Monitor Closely.
- oxazepam
diphenhydramine and oxazepam both increase sedation. Use Caution/Monitor.
- oxybutynin
diphenhydramine and oxybutynin both decrease cholinergic effects/transmission. Use Caution/Monitor.
- oxybutynin topical
diphenhydramine and oxybutynin topical both decrease cholinergic effects/transmission. Use Caution/Monitor.
- oxybutynin transdermal
diphenhydramine and oxybutynin transdermal both decrease cholinergic effects/transmission. Use Caution/Monitor.
- oxycodone
oxycodone increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
diphenhydramine and oxycodone both increase sedation. Use Caution/Monitor.
diphenhydramine will increase the level or effect of oxycodone by affecting hepatic enzyme CYP2D6 metabolism. 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
diphenhydramine will increase the level or effect of oxymorphone by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
diphenhydramine 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
diphenhydramine decreases levels of paliperidone by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
diphenhydramine decreases levels of paliperidone by pharmacodynamic antagonism. Use Caution/Monitor.
paliperidone increases effects of diphenhydramine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.
diphenhydramine 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. - pancuronium
diphenhydramine and pancuronium both decrease cholinergic effects/transmission. Use Caution/Monitor.
- papaveretum
papaveretum increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- papaveretum
diphenhydramine and papaveretum both increase sedation. Use Caution/Monitor.
- papaverine
diphenhydramine and papaverine both increase sedation. Use Caution/Monitor.
- passion flower
passion flower increases effects of diphenhydramine by pharmacodynamic synergism. Use Caution/Monitor. May enhance CNS depression.
- pentazocine
diphenhydramine 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
pentobarbital increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
diphenhydramine and pentobarbital both increase sedation. Use Caution/Monitor. - perampanel
perampanel and diphenhydramine both increase sedation. Use Caution/Monitor.
- 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
diphenhydramine and perphenazine both increase sedation. Use Caution/Monitor.
diphenhydramine decreases levels of perphenazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
diphenhydramine decreases levels of perphenazine by pharmacodynamic antagonism. Use Caution/Monitor.
perphenazine increases effects of diphenhydramine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia. - phendimetrazine
phendimetrazine and phenylephrine both decrease sedation. Use Caution/Monitor.
diphenhydramine 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 diphenhydramine 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.
- phenobarbital
diphenhydramine and phenobarbital both increase sedation. Use Caution/Monitor.
- phentermine
phentermine and phenylephrine both decrease sedation. Use Caution/Monitor.
diphenhydramine 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. - phenylephrine
diphenhydramine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- pholcodine
pholcodine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- phenylephrine PO
diphenhydramine increases and phenylephrine PO decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. .
- pholcodine
diphenhydramine and pholcodine both increase sedation. Use Caution/Monitor.
- physostigmine
physostigmine increases and diphenhydramine decreases cholinergic effects/transmission. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- pilocarpine
pilocarpine increases and diphenhydramine decreases cholinergic effects/transmission. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- pimozide
pimozide increases effects of diphenhydramine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.
diphenhydramine decreases levels of pimozide by pharmacodynamic antagonism. Use Caution/Monitor.
pimozide increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
diphenhydramine and pimozide both increase sedation. Use Caution/Monitor.
diphenhydramine decreases levels of pimozide by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. - pindolol
pindolol increases effects of phenylephrine by pharmacodynamic synergism. Use Caution/Monitor. Risk of acute hypertensive episode (rare).
- pirbuterol
diphenhydramine increases and pirbuterol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- pirbuterol
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. - pralidoxime
diphenhydramine and pralidoxime both decrease cholinergic effects/transmission. Use Caution/Monitor.
- pregabalin
pregabalin, diphenhydramine. 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
primidone increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
diphenhydramine and primidone both increase sedation. Use Caution/Monitor. - prochlorperazine
diphenhydramine and prochlorperazine both increase sedation. Use Caution/Monitor.
diphenhydramine decreases levels of prochlorperazine by pharmacodynamic antagonism. Use Caution/Monitor.
prochlorperazine increases effects of diphenhydramine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.
diphenhydramine decreases levels of prochlorperazine by inhibition of GI absorption. Applies only to oral form of both agents. 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
diphenhydramine and promethazine both increase sedation. Use Caution/Monitor.
diphenhydramine decreases levels of promethazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
diphenhydramine decreases levels of promethazine by pharmacodynamic antagonism. Use Caution/Monitor.
promethazine increases effects of diphenhydramine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia. - 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. - propafenone
diphenhydramine will increase the level or effect of propafenone by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
- propantheline
diphenhydramine and propantheline both decrease cholinergic effects/transmission. Use Caution/Monitor.
- propofol
propofol increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
propofol and diphenhydramine both increase sedation. Use Caution/Monitor. - propranolol
diphenhydramine will increase the level or effect of propranolol by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
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.
phenylephrine and propylhexedrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
diphenhydramine increases and propylhexedrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - protriptyline
diphenhydramine and protriptyline both decrease cholinergic effects/transmission. Use Caution/Monitor.
diphenhydramine 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. - pseudoephedrine
phenylephrine and pseudoephedrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
- pyridostigmine
pyridostigmine increases and diphenhydramine decreases cholinergic effects/transmission. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- quazepam
diphenhydramine 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
diphenhydramine decreases levels of quetiapine by pharmacodynamic antagonism. Use Caution/Monitor.
quetiapine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
diphenhydramine decreases levels of quetiapine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
diphenhydramine and quetiapine both increase sedation. Use Caution/Monitor.
quetiapine increases effects of diphenhydramine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia. - ramelteon
diphenhydramine and ramelteon both increase sedation. Use Caution/Monitor.
- rasagiline
rasagiline increases effects of phenylephrine by pharmacodynamic synergism. Use Caution/Monitor. Risk of acute hypertensive episode.
- rapacuronium
diphenhydramine and rapacuronium both decrease cholinergic effects/transmission. Use Caution/Monitor.
- risperidone
diphenhydramine decreases levels of risperidone by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
diphenhydramine decreases levels of risperidone by pharmacodynamic antagonism. Use Caution/Monitor.
risperidone increases effects of diphenhydramine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.
risperidone increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
diphenhydramine and risperidone both increase sedation. Use Caution/Monitor. - rocuronium
diphenhydramine and rocuronium both decrease cholinergic effects/transmission. Use Caution/Monitor.
- 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.
- salmeterol
diphenhydramine increases and salmeterol decreases sedation. 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. - scopolamine
diphenhydramine and scopolamine both decrease cholinergic effects/transmission. Use Caution/Monitor.
- scullcap
scullcap increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- scullcap
diphenhydramine and scullcap both increase sedation. Use Caution/Monitor.
- secobarbital
secobarbital increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
diphenhydramine 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.
- sevoflurane
sevoflurane and diphenhydramine both increase sedation. Use Caution/Monitor.
- 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. - shepherd's purse
diphenhydramine 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. - solifenacin
diphenhydramine and solifenacin both decrease cholinergic effects/transmission. Use Caution/Monitor.
- solriamfetol
phenylephrine and solriamfetol both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
- stiripentol
stiripentol, diphenhydramine. Either increases effects of the other by sedation. Use Caution/Monitor. Concomitant use stiripentol with other CNS depressants, including alcohol, may increase the risk of sedation and somnolence.
- succinylcholine
succinylcholine increases and diphenhydramine decreases cholinergic effects/transmission. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- sufentanil
sufentanil increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
diphenhydramine and sufentanil both increase sedation. Use Caution/Monitor. - tamoxifen
diphenhydramine decreases effects of tamoxifen by decreasing metabolism. Use Caution/Monitor. Inhibition of CYP2D6 metabolism to tamoxifen's active metabolite, endoxifen.
- tapentadol
tapentadol increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- tamsulosin
diphenhydramine increases levels of tamsulosin by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
- tapentadol
diphenhydramine and tapentadol both increase sedation. Use Caution/Monitor.
- tazemetostat
acetaminophen will increase the level or effect of tazemetostat by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- temazepam
temazepam increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
diphenhydramine and temazepam both increase sedation. 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.
diphenhydramine increases and terbutaline decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - tetracaine
tetracaine, acetaminophen. Other (see comment). Use Caution/Monitor. Comment: Monitor for signs of methemoglobinemia when methemoglobin-inducing drugs are coadministered.
- thioridazine
diphenhydramine decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
diphenhydramine decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
thioridazine increases effects of diphenhydramine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.
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.
diphenhydramine and thioridazine both increase sedation. Use Caution/Monitor. - thiothixene
diphenhydramine and thiothixene both increase sedation. Use Caution/Monitor.
diphenhydramine decreases levels of thiothixene by pharmacodynamic antagonism. Use Caution/Monitor.
thiothixene increases effects of diphenhydramine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.
diphenhydramine decreases levels of thiothixene by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
thiothixene increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - timolol
diphenhydramine will increase the level or effect of timolol by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
timolol increases effects of phenylephrine by pharmacodynamic synergism. Use Caution/Monitor. Risk of acute hypertensive episode (rare). - tinidazole
acetaminophen will increase the level or effect of tinidazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- tiotropium
diphenhydramine and tiotropium both decrease cholinergic effects/transmission. Use Caution/Monitor.
- topiramate
topiramate increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
- tolterodine
diphenhydramine and tolterodine both decrease cholinergic effects/transmission. Use Caution/Monitor.
- topiramate
diphenhydramine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- tramadol
diphenhydramine decreases effects of tramadol by decreasing metabolism. Use Caution/Monitor. Decreased conversion of tramadol to active metabolite.
diphenhydramine decreases effects of tramadol by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Decreased conversion of tramadol to active metabolite.
diphenhydramine 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. - trazodone
diphenhydramine and trazodone both increase sedation. Use Caution/Monitor.
trazodone increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - triazolam
triazolam increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
diphenhydramine and triazolam both increase sedation. Use Caution/Monitor. - triclofos
diphenhydramine 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
diphenhydramine and trifluoperazine both increase sedation. Use Caution/Monitor.
diphenhydramine decreases levels of trifluoperazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
diphenhydramine decreases levels of trifluoperazine by pharmacodynamic antagonism. 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.
trifluoperazine increases effects of diphenhydramine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia. - trihexyphenidyl
diphenhydramine and trihexyphenidyl both decrease cholinergic effects/transmission. Use Caution/Monitor. Potential for additive anticholinergic effects.
- trimipramine
trimipramine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- trimipramine
diphenhydramine and trimipramine both decrease cholinergic effects/transmission. Use Caution/Monitor.
diphenhydramine 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.
diphenhydramine and triprolidine both increase sedation. Use Caution/Monitor. - trospium chloride
diphenhydramine and trospium chloride both decrease cholinergic effects/transmission. Use Caution/Monitor.
- warfarin
acetaminophen increases effects of warfarin by anticoagulation. Use Caution/Monitor.
- 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.
Minor (88)
- acetazolamide
acetazolamide decreases levels of acetaminophen by increasing metabolism. Minor/Significance Unknown. Enhanced metabolism incr levels of hepatotoxic metabolites.
- albiglutide
albiglutide decreases levels of acetaminophen by unspecified interaction mechanism. Minor/Significance Unknown.
- alfuzosin
alfuzosin, phenylephrine. Either decreases effects of the other by Mechanism: pharmacodynamic antagonism. Minor/Significance Unknown.
- antithrombin alfa
acetaminophen increases effects of antithrombin alfa by unknown mechanism. Minor/Significance Unknown.
- antithrombin III
acetaminophen increases effects of antithrombin III by unknown mechanism. Minor/Significance Unknown.
- argatroban
acetaminophen increases effects of argatroban by unknown mechanism. Minor/Significance Unknown.
- aripiprazole
diphenhydramine will increase the level or effect of aripiprazole by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
- asenapine
asenapine, phenylephrine. Either decreases effects of the other by Mechanism: pharmacodynamic antagonism. Minor/Significance Unknown.
- ashwagandha
ashwagandha increases effects of diphenhydramine by pharmacodynamic synergism. Minor/Significance Unknown. May enhance CNS depression.
- bemiparin
acetaminophen increases effects of bemiparin by unknown mechanism. Minor/Significance Unknown.
- bivalirudin
acetaminophen increases effects of bivalirudin by unknown mechanism. Minor/Significance Unknown.
- brimonidine
brimonidine increases effects of diphenhydramine by pharmacodynamic synergism. Minor/Significance Unknown. Increased CNS depression.
- carbamazepine
carbamazepine decreases levels of acetaminophen by increasing metabolism. Minor/Significance Unknown. Enhanced metabolism incr levels of hepatotoxic metabolites.
- chlorpromazine
diphenhydramine will increase the level or effect of chlorpromazine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
- cholestyramine
cholestyramine decreases levels of acetaminophen by inhibition of GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown.
- clonazepam
clonazepam decreases levels of acetaminophen by increasing metabolism. Minor/Significance Unknown. Enhanced metabolism incr levels of hepatotoxic metabolites.
- colestipol
colestipol decreases levels of acetaminophen by inhibition of GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown.
- dalteparin
acetaminophen increases effects of dalteparin by unknown mechanism. Minor/Significance Unknown.
- desipramine
diphenhydramine and desipramine both decrease cholinergic effects/transmission. Minor/Significance Unknown.
desipramine and diphenhydramine both decrease cholinergic effects/transmission. Minor/Significance Unknown. - desmopressin
desmopressin increases effects of phenylephrine by pharmacodynamic synergism. Minor/Significance Unknown.
- dexfenfluramine
diphenhydramine will increase the level or effect of dexfenfluramine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
- dextroamphetamine
diphenhydramine will increase the level or effect of dextroamphetamine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
- dextromethorphan
diphenhydramine will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
- diazepam
diazepam decreases levels of acetaminophen by increasing metabolism. Minor/Significance Unknown. Enhanced metabolism incr levels of hepatotoxic metabolites.
- dimenhydrinate
dimenhydrinate increases toxicity of diphenhydramine by pharmacodynamic synergism. Minor/Significance Unknown. Additive anticholinergic effects.
- disulfiram
disulfiram will increase the level or effect of acetaminophen by affecting hepatic enzyme CYP2E1 metabolism. Minor/Significance Unknown.
- donepezil
diphenhydramine will increase the level or effect of donepezil by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
donepezil decreases effects of diphenhydramine by pharmacodynamic antagonism. Minor/Significance Unknown. - doxazosin
doxazosin, phenylephrine. Either decreases effects of the other by Mechanism: pharmacodynamic antagonism. Minor/Significance Unknown.
- doxepin
diphenhydramine will increase the level or effect of doxepin by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
- encainide
diphenhydramine will increase the level or effect of encainide by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
- enoxaparin
acetaminophen increases effects of enoxaparin by unknown mechanism. Minor/Significance Unknown.
- ethanol
ethanol will decrease the level or effect of acetaminophen by affecting hepatic enzyme CYP2E1 metabolism. Minor/Significance Unknown.
ethanol increases toxicity of acetaminophen by decreasing metabolism. Minor/Significance Unknown. - ethosuximide
ethosuximide decreases levels of acetaminophen by increasing metabolism. Minor/Significance Unknown. Enhanced metabolism incr levels of hepatotoxic metabolites.
- eucalyptus
eucalyptus increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Minor/Significance Unknown.
diphenhydramine and eucalyptus both increase sedation. Minor/Significance Unknown. - felbamate
felbamate decreases levels of acetaminophen by increasing metabolism. Minor/Significance Unknown. Enhanced metabolism incr levels of hepatotoxic metabolites.
- fesoterodine
diphenhydramine will increase the level or effect of fesoterodine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
- fondaparinux
acetaminophen increases effects of fondaparinux by unknown mechanism. Minor/Significance Unknown.
- fosphenytoin
fosphenytoin decreases levels of acetaminophen by increasing metabolism. Minor/Significance Unknown. Enhanced metabolism incr levels of hepatotoxic metabolites.
- green tea
green tea increases effects of acetaminophen by pharmacodynamic synergism. Minor/Significance Unknown. (Theoretical, due to caffeine content).
- heparin
acetaminophen increases effects of heparin by unknown mechanism. Minor/Significance Unknown.
- isoniazid
isoniazid increases toxicity of acetaminophen by unknown mechanism. Minor/Significance Unknown.
- lacosamide
lacosamide decreases levels of acetaminophen by increasing metabolism. Minor/Significance Unknown. Enhanced metabolism incr levels of hepatotoxic metabolites.
- lamotrigine
lamotrigine decreases levels of acetaminophen by increasing metabolism. Minor/Significance Unknown. Enhanced metabolism incr levels of hepatotoxic metabolites.
- levetiracetam
levetiracetam decreases levels of acetaminophen by increasing metabolism. Minor/Significance Unknown. Enhanced metabolism incr levels of hepatotoxic metabolites.
- liraglutide
liraglutide decreases levels of acetaminophen by unspecified interaction mechanism. Minor/Significance Unknown.
- lorazepam
lorazepam decreases levels of acetaminophen by increasing metabolism. Minor/Significance Unknown. Enhanced metabolism incr levels of hepatotoxic metabolites.
- methsuximide
methsuximide decreases levels of acetaminophen by increasing metabolism. Minor/Significance Unknown. Enhanced metabolism incr levels of hepatotoxic metabolites.
- metoclopramide
metoclopramide increases levels of acetaminophen by enhancing GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown.
- metronidazole
metronidazole will increase the level or effect of acetaminophen by affecting hepatic enzyme CYP2E1 metabolism. Minor/Significance Unknown.
- moxisylyte
moxisylyte, phenylephrine. Either decreases effects of the other by Mechanism: pharmacodynamic antagonism. Minor/Significance Unknown.
- fluoxetine
diphenhydramine will increase the level or effect of fluoxetine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
- fluphenazine
diphenhydramine will increase the level or effect of fluphenazine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
- galantamine
diphenhydramine will increase the level or effect of galantamine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
galantamine decreases effects of diphenhydramine by pharmacodynamic antagonism. Minor/Significance Unknown. - loratadine
diphenhydramine will increase the level or effect of loratadine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
- nettle
nettle increases effects of diphenhydramine by pharmacodynamic synergism. Minor/Significance Unknown. (High dose nettle; theoretical interaction) May enhance CNS depression.
- nitazoxanide
nitazoxanide, diphenhydramine. Either increases levels of the other by Mechanism: plasma protein binding competition. Minor/Significance Unknown.
- oxcarbazepine
oxcarbazepine decreases levels of acetaminophen by increasing metabolism. Minor/Significance Unknown. Enhanced metabolism incr levels of hepatotoxic metabolites.
- oxybutynin
oxybutynin decreases levels of acetaminophen by unspecified interaction mechanism. Minor/Significance Unknown.
- oxybutynin topical
oxybutynin topical decreases levels of acetaminophen by unspecified interaction mechanism. Minor/Significance Unknown.
- oxybutynin transdermal
oxybutynin transdermal decreases levels of acetaminophen by unspecified interaction mechanism. Minor/Significance Unknown.
- oxycodone
diphenhydramine decreases effects of oxycodone by decreasing metabolism. Minor/Significance Unknown. Decreased conversion of oxycodone to active metabolite morphine.
- paroxetine
diphenhydramine will increase the level or effect of paroxetine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
- perhexiline
diphenhydramine will increase the level or effect of perhexiline by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
- perphenazine
diphenhydramine will increase the level or effect of perphenazine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
- phenindione
acetaminophen increases effects of phenindione by unknown mechanism. Minor/Significance Unknown.
- phenobarbital
phenobarbital decreases levels of acetaminophen by increasing metabolism. Minor/Significance Unknown. Enhanced metabolism incr levels of hepatotoxic metabolites.
- 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.
- phenytoin
phenytoin decreases levels of acetaminophen by increasing metabolism. Minor/Significance Unknown. Enhanced metabolism incr levels of hepatotoxic metabolites.
- prazosin
prazosin, phenylephrine. Either decreases effects of the other by Mechanism: pharmacodynamic antagonism. Minor/Significance Unknown.
- primidone
primidone decreases levels of acetaminophen by increasing metabolism. Minor/Significance Unknown. Enhanced metabolism incr levels of hepatotoxic metabolites.
- prochlorperazine
diphenhydramine will increase the level or effect of prochlorperazine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
- promazine
diphenhydramine will increase the level or effect of promazine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
- promethazine
diphenhydramine will increase the level or effect of promethazine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
- protamine
acetaminophen increases effects of protamine by unknown mechanism. Minor/Significance Unknown.
- rifabutin
rifabutin decreases levels of acetaminophen by increasing metabolism. Minor/Significance Unknown. Enhanced metabolism incr levels of hepatotoxic metabolites.
- rifampin
rifampin decreases levels of acetaminophen by increasing metabolism. Minor/Significance Unknown. Enhanced metabolism incr levels of hepatotoxic metabolites.
- risperidone
diphenhydramine will increase the level or effect of risperidone by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
- rufinamide
rufinamide decreases levels of acetaminophen by increasing metabolism. Minor/Significance Unknown. Enhanced metabolism incr levels of hepatotoxic metabolites.
- ruxolitinib
acetaminophen will increase the level or effect of ruxolitinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- ruxolitinib topical
acetaminophen will increase the level or effect of ruxolitinib topical by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- sage
sage increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Minor/Significance Unknown.
diphenhydramine and sage both increase sedation. Minor/Significance Unknown. - Siberian ginseng
Siberian ginseng increases effects of diphenhydramine 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.
- terazosin
terazosin, phenylephrine. Either decreases effects of the other by Mechanism: pharmacodynamic antagonism. Minor/Significance Unknown.
- tiagabine
tiagabine decreases levels of acetaminophen by increasing metabolism. Minor/Significance Unknown. Enhanced metabolism incr levels of hepatotoxic metabolites.
- tolterodine
diphenhydramine will increase the level or effect of tolterodine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
- topiramate
topiramate decreases levels of acetaminophen by increasing metabolism. Minor/Significance Unknown. Enhanced metabolism incr levels of hepatotoxic metabolites.
Adverse Effects
Frequency Not Defined
Hypertension
Hypotension
Reflex tachycardia
Severe peripheral and visceral vasoconstriction
Tachycardia
Dizziness
Excitability
Headache
Restlessness
Sedation
Sleepiness
Tremor
Dermatologic rash
Increased appetite
Xerostomia
Anemia blood dyscrasias (neutropenia, pancytopenia, leukopenia)
Bilirubin and alkaline phosphatase may increase
Urinary retention
Warnings
Contraindications
Hypersensitivity
Use within 14 days of MAO inhibitor therapy
To sedate child
Children <12 years
Concomitant administration with other products containing acetaminophen or diphenhydramine
Cautions
Ask healthcare professional if history of asthma or COPD, cough with mucus, or couch caused by smoking, emphysema, or chronic bronchitis, high blood pressure, heart disease, enlarged prostate, urination problems, thyroid disorder, diabetes, glaucoma, or diagnosed with condition requiring warfarin therapy
Medication is to be used exactly as directed; an overdose of acetaminophen can damage the liver or cause death; taking too much diphenhydramine can lead to serious heart problems, seizures, coma, or death
Not for use to make a child sleepy; some brands are not approved for use in anyone younger than 12 years old
Dangerous drug interaction can occur with MAO inhibitors, including isocarboxazid, linezolid, phenelzine, rasagiline, selegiline, and tranylcypromine
Cardiovascular disease (bradycardia, partial heart block or severe arteriosclerosis when administering phenylephrine)
Acetaminophen hepatotoxicity possible in chronic alcoholics following various dose levels; before taking this medication, ask healthcare professional if experienced previous liver disease, or if taking more than 3 alcoholic beverages per day
Acetaminophen: Risk for rare, but serious skin reactions that can be fatal; these reactions include Stevens-Johnson Syndrome (SJS), toxic epidermal necrolysis (TEN), and acute generalized exanthematous pustulosis (AGEP); symptoms may include skin redness, blisters and rash
Severe or recurrent pain or high or continued fever may indicate a serious illness
Acetaminophen contained in many OTC products and combined use with these products may result in toxicity due to cumulative doses exceeding recommended maximum dose
Diphenhydramine may cause significant confusional symptoms
Diphenhydramine not for administration to premature or full-term neonates
Pregnancy & Lactation
Pregnancy
Ask a healthcare professional
Lactation
Ask a healthcare professional
Pregnancy Categories
A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.
B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk. C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done. D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk. X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist. NA: Information not available.Pharmacology
Mechanism of Action
Acetaminophen: Blocks pain impulse generation peripherally & may inhibit the prostaglandin generation in CNS; reduces fever by inhibiting hypothalamic heat-regulating center
Phenylephrine: Vasoconstrictor & decongestant that relieves symptoms resulting from irritation of upper respiratory tract tissue; shrinks swollen mucous membranes, reduces nasal congestion & tissue hyperemia
Diphenhydramine: Competitively blocks histamine from binding to H1 receptors; significant antimuscarinic activity & penetrates CNS, which causes pronounced tendency to induce sedation