warfarin (Rx)

Venous Thrombosis

Prophylaxis and treatment of venous thrombosis and its extension, pulmonary embolism (PE)

Initial dose: 2-5 mg PO/IV qDay for 2 days, OR 10 mg PO for 2 days in healthy individuals

Initiate warfarin on day 1 or 2 of LMWH or unfractionated heparin therapy and overlap until desired INR, THEN discontinue heparin

Check INR after 2 days and adjust dose according to results

Typical maintenance dose ranges between 2 and 10 mg/day

Consider dosage based on genotype (see Genomic Considerations)

DVT and PE treatment

• Initiate warfarin on day 1 or 2 of parenteral anticoagulation therapy (eg, LMWH or unfractionated heparin)
• Overlap warfarin and parenteral anticoagulant for at least 5 days until desired INR (>2.0) maintained for 24 hours, then discontinue parenteral therapy

INR range and treatment duration

• Maintain an INR of 2.0-3.0
• Surgery-provoked DVT or PE: Treatment duration of 3 months
• Transient (reversible) risk factor-induced DVT or PE: Treatment duration of 3 months
• First unprovoked proximal DVT or PE with low or moderate bleeding risk: Extended treatment consideration with periodic (ie, annual) risk-benefit analysis
• First unprovoked proximal DVT or PE with high bleeding risk: Treatment duration of 3 months
• First unprovoked distal DVT regardless of bleeding risk: Treatment duration of 3 months
• Second unprovoked DVT or PE with low or moderate bleeding risk: Extended treatment
• Second unprovoked DVT or PE with high bleeding risk: Treatment duration of 3 months
• DVT/PE and active cancer: Extended treatment, with periodic risk-benefit analysis (ACCP recommends LMWH over vitamin K antagonist therapy)
• Prevention of venous thromboembolism for total knee arthroplasty, total hip arthroplasty, and hip fracture surgery: Minimum treatment duration of 10-14 days, with a recommendation to extend outpatient therapy to 35 days (ACCP recommends LMWH over vitamin K antagonist therapy)

Stroke & Thromboembolism

Prophylaxis and treatment of systemic embolic complications (eg, stroke) associated with atrial fibrillation (AF)

Initial dose: 2-5 mg PO/IV qDay × 2 days, OR 10 mg PO × 2 days in healthy individuals

Check INR after 2 days and adjust dose according to results

Typical maintenance dose ranges between 2-10 mg/day

Consider dosage based on genotype (see Genomic Considerations)

ACCP guidelines recommend dabigatran 150 mg PO BID over adjusted-dose warfarin therapy for AF unless both AF and mitral stenosis are present

INR range and treatment duration

• Nonvalvular AF: Maintain an INR of 2.0-3.0
• AF and stable CAD: Adjusted-dose warfarin therapy (INR 2.0-3.0) without aspirin
• AF with high stroke risk and placement of stent: Triple therapy of dose-adjusted warfarin (INR 2.0-3.0), clopidogrel, and aspirin; for 1 month if bare metal stent; for 3-6 months for drug-eluting stent
• AF with intermediate to high stroke risk without stent placement: 12 months of warfarin therapy (INR 2.0-3.0) with single antiplatelet regimen
• AF for more than 48 hours to undergo cardioversion: Warfarin therapy (INR 2.0-3.0) for 3 weeks prior to and 4 weeks after cardioversion

Indications for indefinite treatment duration

• Persistent or paroxysmal nonvalvular AF in patients with a high risk of stroke: Ie, patients who have risk factors for stroke, such as prior ischemic stroke, transient ischemic attack, or systemic embolism or who have 2 of the following risk factors--age greater than 75 years, moderately or severely impaired left ventricular systolic function and/or heart failure, history of hypertension, or diabetes mellitus
• Persistent or paroxysmal nonvalvular AF in patients with an intermediate risk of ischemic stroke: Ie, patients who have 1 of the following risk factors--age >75 years, moderately or severely impaired left ventricular systolic function and/or heart failure, history of hypertension, or diabetes mellitus
• AF and mitral stenosis
• ≥2 episodes of documented DVT or PE

Cardiac Valve Replacement

Prophylaxis and treatment of thromboembolic complications associated with cardiac valve replacement

Initial dose: 2-5 mg PO/IV qDay × 2 days, OR 10 mg PO × 2 days in healthy individuals

Check INR after 2 days and adjust dose according to results

Typical maintenance dose ranges between 2 and 10 mg/day

Consider dosage based on genotype (see Genomic Considerations)

INR and treatment duration

• Mitral bioprosthetic valve: INR 2.0-3.0 for a 3-month treatment duration; if other risk factors for thromboembolism are present (ie, AF, previous thromboembolism, left ventricular dysfunction), a longer duration may be necessary
• Aortic mechanical valve: INR 2.0-3.0 for indefinite treatment duration
• Mitral mechanical valve, caged ball or caged disk valve, or both aortic and mitral mechanical valves: INR 2.5-3.5 for indefinite treatment duration
• Mechanical valves include bileaflet mechanical valves and Medtronic Hall tilting disk valves

Post-Myocardial Infarction

Reduction in the risk of death, recurrent MI, and thromboembolic events (eg, stroke, systemic embolization) after MI

Initial dose: 2-5 mg PO/IV qDay × 2 days, OR 10 mg PO × 2 days in healthy individuals

Check INR after 2 days and adjust dose according to results

Typical maintenance dose ranges between 2 and 10 mg/day

Consider dosage based on genotype (see Genomic Considerations)

INR and treatment duration

• Maintain INR between 2.0 and 3.0
• In patients who have not had stenting and who have anterior MI and left ventricular (LV) thrombus or high risk of LV thrombus (ie, ejection fraction <40%, anteroapical wall-motion abnormality), treatment involves dual therapy of warfarin (INR 2.0-3.0) and low-dose aspirin 75-100 mg, daily; treatment duration is 3 months, after which warfarin is discontinued
• In patients who have had bare-metal stent placement and who have anterior MI and LV thrombus or high risk of LV thrombus (ejection fraction <40%, anteroapical wall-motion abnormality), treatment involves triple therapy of warfarin (INR 2.0-3.0), low-dose aspirin, and clopidogrel 75 mg, daily for 1 month, followed by warfarin (INR 2.0-3.0) and single antiplatelet therapy for second and third month, after which warfarin is discontinued
• In patients who have had drug-eluting stent placement and who have anterior MI and LV thrombus or high risk of LV thrombus (ejection fraction <40%, anteroapical wall-motion abnormality), treatment involves triple therapy of warfarin (INR 2.0-3.0), low-dose aspirin, and clopidogrel 75 mg, daily for 3-6 months, after which warfarin is discontinued

Rheumatic Valve Disease (Off-label)

Rheumatic valve disease with any of the following: Atrial diameter >55 mm, left atrial thrombus, atrial fibrillation, and previous systemic embolism

Maintain INR 2.0-3.0 indefinitely

Cryptogenic Stroke and Patent Foramen Ovale With DVT (Off-label)

Maintain INR between 2.0 and 3.0 for 3 months

Cardioembolic Stroke or TIA (Off-label)

Maintain INR between 2.0 and 3.0 indefinitely

ACCP guidelines recommend dabigatran 150 mg PO twice daily over dose-adjusted warfarin therapy

Systolic LV Dysfunction (Off-label)

Systolic LV dysfunction without established CAD but with identified acute LV thrombus (eg, Takotsubo cardiomyopathy)

Maintain INR between 2.0 and 3.0 for at least 3 months

Antiphospholipid Antibody Syndrome (Off-label)

Antiphospholipid antibody syndrome with previous arterial or venous thromboembolism

Maintain INR between 2.0 and 3.0 indefinitely

Genomic Considerations

ACCP 2012 guidelines recommend against using pharmacogenetic testing for guiding doses

CYP2C9 and vitamin K epoxide reductase complex, subunit 1 (VKORC1) genotype information can assist in selecting starting dose

If genotype information unavailable, usual starting dose is 2-5 mg/day (modify based on other patient factors)

Range of expected therapeutic doses based on CYP2C9 and VKORC1 genotypes are listed below

VKORC1-GG

• CYP2C9 *1/*1: 5-7 mg
• CYP2C9 *1/*2: 5-7 mg
• CYP2C9 *1/*3: 3-4 mg
• CYP2C9 *2/*2: 3-4 mg
• CYP2C9 *2/*3: 3-4 mg
• CYP2C9 *3/*3: 0.5-2 mg

VKORC1-AG

• CYP2C9 *1/*1: 5-7 mg
• CYP2C9 *1/*2: 3-4 mg
• CYP2C9 *1/*3: 3-4 mg
• CYP2C9 *2/*2: 3-4 mg
• CYP2C9 *2/*3: 0.5-2 mg
• CYP2C9 *3/*3: 0.5-2 mg

VKORC1-AA

• CYP2C9 *1/*1: 3-4 mg
• CYP2C9 *1/*2: 3-4 mg
• CYP2C9 *1/*3: 0.5-2 mg
• CYP2C9 *2/*2: 0.5-2 mg
• CYP2C9 *2/*3: 0.5-2 mg
• CYP2C9 *3/*3: 0.5-2 mg

Dosage Modifications

Hepatic impairment: May potentiate warfarin response because of decreased metabolism and impaired synthesis of clotting factors

Dosing Considerations

Indication determines intensity and duration of therapy

Individualized doses and monitoring of PT/INR are necessary

Monitoring frequency should be daily or once every few days until stabilized; once stable, q4-6 weeks or longer may be appropriate (eg, 12 weeks)

Not all factors causing warfarin dose variability are known, but they include age, race, sex, body weight, concomitant medications, and comorbidities, in addition to genetic factors

Lower starting doses (ie, 2-5 mg/day × 2 days) recommended with the elderly, hepatic impairment, poor nutrition, CHF, high bleeding risk, debilitated patients, heart valve replacement, concomitant medications known to increase warfarin effect, or individuals suspected of having genomic variants

Perioperative management recommendations: Hold warfarin therapy approximately 5 days before surgery; resume warfarin 12-24 hr after surgery; bridge anticoagulation during interruption in patients at high thromboembolism risk

Minor procedures and dental procedures: See ACCP guidelines for specific recommendations

Warfarin has no direct effect on an established thrombus, nor does it reverse ischemic tissue damage

Systemic atheroemboli and cholesterol microemboli; some cases have progressed to necrosis or death; discontinue therapy if such emboli occur

Pregnant women with mechanical heart valves: Therapy may cause fetal harm; however, benefits may outweigh the risks

Thrombosis

Prevention/treatment: If baseline INR is 1.0-1.3, administer loading dose of 0.1-0.2 mg/kg PO qDay × 1 day; check INR on days 2-4 and adjust daily dose to maintain INR between 2.0 and 3.0 (unless valve replacement indicates a higher range)  

Use 0.1 mg/kg to initiate therapy with liver impairment or in patients who have had a Fontan procedure

Typical maintenance dose: 0.09-0.33 mg/kg/day, with infants <12 months old often requiring doses at high end of range

Dosing considerations

• Consistent anticoagulation in children is difficult and requires close supervision and frequent dose adjustments
• Refer to ACCP recommendations or institutional protocol for treatment duration dependent on indication
• Infants and children receiving vitamin K-supplemented nutrition (including infant formulas): May be resistant to warfarin therapy
• Infants with human-milk diet: May be sensitive to warfarin therapy

Dosing Considerations

Hepatic impairment

• Hepatic impairment may potentiate warfarin response because of decreased metabolism and impaired synthesis of clotting factors
• Load: 0.1 mg/kg PO qDay × 2 days
• Typical maintenance dose: 0.1 mg/kg PO qDay; adjust dose to achieve desired INR
• Common maintenance dose range: 0.05-0.34 mg/kg PO qDay

Anticoagulation

Lower doses required to produce therapeutic level of anticoagulation

Initial: ≤5 mg PO qDay

Maintenance: 2-5 mg PO qDay

Dosing Considerations

Elderly show greater than expected PT/INR response to anticoagulant effects of warfarin, possibly because of decreased hepatic function resulting in decreased warfarin metabolism and impaired synthesis of clotting factors

Caution should be used in elderly individuals who have increased risk of hemorrhage

Contraindicated (3)

• defibrotide

  defibrotide, warfarin. Either increases effects of the other by pharmacodynamic synergism. Contraindicated. Defibrotide is contraindicated with systemic anticoagulants. .

• mifepristone

  mifepristone increases effects of warfarin by anticoagulation. Contraindicated.

• omacetaxine

  omacetaxine increases effects of warfarin by anticoagulation. Contraindicated.

Serious - Use Alternative (24)

• adagrasib

  adagrasib will increase the level or effect of warfarin by Other (see comment). Avoid or Use Alternate Drug. Avoid coadministration of adagrasib, a CYP3A4 and CYP2C9 inhibitor, with warfarin, a sensitive CYP3A and CYP2C9 substrate, unless otherwise recommended in the prescribing information for warfarin.

• allopurinol

  allopurinol increases effects of warfarin by anticoagulation. Avoid or Use Alternate Drug.

• apixaban

  apixaban increases effects of warfarin by anticoagulation. Avoid or Use Alternate Drug. Avoid combined use once INR is established in the desired therapeutic range.

• argatroban

  argatroban increases effects of warfarin by anticoagulation. Avoid or Use Alternate Drug. Avoid combined use once INR is established in the desired therapeutic range.

• betrixaban

  betrixaban increases effects of warfarin by anticoagulation. Avoid or Use Alternate Drug. Avoid combined use once INR is established in the desired therapeutic range.

• bismuth subsalicylate

  bismuth subsalicylate increases effects of warfarin by anticoagulation. Avoid or Use Alternate Drug.

• bivalirudin

  bivalirudin increases effects of warfarin by anticoagulation. Avoid or Use Alternate Drug. Avoid combined use once INR is established in the desired therapeutic range.

• cholestyramine

  cholestyramine decreases effects of warfarin by inhibition of GI absorption. Applies only to oral form of both agents. Avoid or Use Alternate Drug. Cholestyramine and vitamin K antagonists should be administered 3-4 hr apart and monitor patients closely for reduced vitamin K antagonist effects.

• choline magnesium trisalicylate

  choline magnesium trisalicylate increases effects of warfarin by anticoagulation. Avoid or Use Alternate Drug.

• cimetidine

  cimetidine increases effects of warfarin by unspecified interaction mechanism. Avoid or Use Alternate Drug.

• dabigatran

  dabigatran increases effects of warfarin by anticoagulation. Avoid or Use Alternate Drug. Avoid combined use once INR is established in the desired therapeutic range.

• danazol

  danazol increases effects of warfarin by anticoagulation. Avoid or Use Alternate Drug.

• edoxaban

  edoxaban increases effects of warfarin by anticoagulation. Avoid or Use Alternate Drug. Avoid combined use once INR is established in the desired therapeutic range.

• fluoxymesterone

  fluoxymesterone increases effects of warfarin by anticoagulation. Avoid or Use Alternate Drug.

• fondaparinux

  fondaparinux increases effects of warfarin by anticoagulation. Avoid or Use Alternate Drug. Avoid combined use once INR is established in the desired therapeutic range.

• heparin

  heparin increases effects of warfarin by anticoagulation. Avoid or Use Alternate Drug. Avoid combined use once INR is established in the desired therapeutic range.

• magnesium salicylate

  magnesium salicylate increases effects of warfarin by anticoagulation. Avoid or Use Alternate Drug.

• methyltestosterone

  methyltestosterone increases effects of warfarin by anticoagulation. Avoid or Use Alternate Drug.

• olutasidenib

  olutasidenib will decrease the level or effect of warfarin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of olutasidenib (a CYP3A4 inducer) with sensitive CYP3A substrates unless otherwise instructed in substrates prescribing information. If unavoidable, monitor for loss of therapeutic effect of sensitive CYP3A4 substrates.

• oxandrolone

  oxandrolone increases effects of warfarin by anticoagulation. Avoid or Use Alternate Drug.

• oxymetholone

  oxymetholone increases effects of warfarin by anticoagulation. Avoid or Use Alternate Drug.

• rivaroxaban

  rivaroxaban increases effects of warfarin by anticoagulation. Avoid or Use Alternate Drug. Avoid combined use once INR is established in the desired therapeutic range.

• testosterone

  testosterone increases effects of warfarin by anticoagulation. Avoid or Use Alternate Drug.

• vorapaxar

  vorapaxar increases effects of warfarin by anticoagulation. Avoid or Use Alternate Drug.

Monitor Closely (296)

• abciximab

  abciximab, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• acalabrutinib

  acalabrutinib increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• acetaminophen

  acetaminophen increases effects of warfarin by anticoagulation. Use Caution/Monitor.

• acetaminophen IV

  acetaminophen IV increases effects of warfarin by anticoagulation. Use Caution/Monitor. Likely to occur at doses exceedin 1.3-2 g/day for multiple consecutive days.

• acetaminophen rectal

  acetaminophen rectal increases effects of warfarin by anticoagulation. Use Caution/Monitor. Likely to occur at doses exceedin 1.3-2 g/day for multiple consecutive days.

• acetaminophen/pamabrom

  acetaminophen/pamabrom increases effects of warfarin by anticoagulation. Use Caution/Monitor. Likely to occur at doses exceedin 1.3-2 g/day acetaminophen for multiple consecutive days.

• acetaminophen/phenyltoloxamine

  acetaminophen/phenyltoloxamine increases effects of warfarin by anticoagulation. Use Caution/Monitor. Likely to occur at doses exceedin 1.3-2 g/day acetaminophen for multiple consecutive days.

• alpelisib

  alpelisib will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• aminosalicylic acid

  aminosalicylic acid increases effects of warfarin by anticoagulation. Use Caution/Monitor.

• amiodarone

  amiodarone will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely. Coadministration increases INR by 100% after 3-4 days. Reduce warfarin dose by one-third to one-half and monitor INR.

• amitriptyline

  amitriptyline increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• amobarbital

  amobarbital will decrease the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inducers of these isoenzymes and adjust warfarin dose if needed.

• anagrelide

  anagrelide, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• apalutamide

  apalutamide will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• aprepitant

  aprepitant will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely. In patients on chronic warfarin therapy, monitor INR in the 2-week period, particularly at 7-10 days, following aprepitant or fosaprepitant administration with each chemotherapy cycle

• armodafinil

  armodafinil will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• asciminib

  asciminib will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.

• aspirin

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

• atazanavir

  atazanavir will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• atovaquone

  atovaquone increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• azathioprine

  azathioprine decreases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• azithromycin

  azithromycin increases toxicity of warfarin by anticoagulation. Use Caution/Monitor. Postmarketing reports have suggested that concomitant administration of azithromycin may potentiate effects of oral warfarin but the interaction does not appear to alter prothrombin time.

• balsalazide

  balsalazide increases effects of warfarin by anticoagulation. Use Caution/Monitor.

• belzutifan

  belzutifan will decrease the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inducers of these isoenzymes and adjust warfarin dose if needed.

• benzhydrocodone/acetaminophen

  benzhydrocodone/acetaminophen increases effects of warfarin by anticoagulation. Use Caution/Monitor. Likely to occur at doses exceedin 1.3-2 g/day acetamionphen for multiple consecutive days.

• betamethasone

  betamethasone increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• bexarotene

  bexarotene will decrease the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inducers of these isoenzymes and adjust warfarin dose if needed.

• bicalutamide

  bicalutamide increases effects of warfarin by Other (see comment). Use Caution/Monitor. Comment: May increase free concentrations of vitamin K antagonists.

• bosentan

  bosentan will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• butalbital

  butalbital will decrease the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inducers of these isoenzymes and adjust warfarin dose if needed.

• cangrelor

  cangrelor, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• capecitabine

  capecitabine will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely. Closely monitor INR and PT and adjust dose. Increased INR and PT can occur within a few days of initiating capecitabine.

• carbamazepine

  carbamazepine will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• cefaclor

  cefaclor increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• cefadroxil

  cefadroxil increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• cefazolin

  cefazolin increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• cefdinir

  cefdinir increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• cefditoren

  cefditoren increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• cefepime

  cefepime increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• cefiderocol

  cefiderocol increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• cefixime

  cefixime increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• cefotaxime

  cefotaxime increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• cefotetan

  cefotetan increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• cefoxitin

  cefoxitin increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• cefpodoxime

  cefpodoxime increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• cefprozil

  cefprozil increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• ceftaroline

  ceftaroline increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• ceftazidime

  ceftazidime increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• ceftibuten

  ceftibuten increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• ceftolozane/tazobactam

  ceftolozane/tazobactam increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• ceftriaxone

  ceftriaxone increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• cefuroxime

  cefuroxime increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• celecoxib

  celecoxib increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• cenobamate

  cenobamate will decrease the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inducers of these isoenzymes and adjust warfarin dose if needed.

• cephalexin

  cephalexin increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• ceritinib

  ceritinib will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.

• chenodiol

  chenodiol increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• chloral hydrate

  chloral hydrate increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• chloramphenicol

  chloramphenicol will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• chlorpropamide

  chlorpropamide, warfarin. Either increases effects of the other by receptor binding competition. Use Caution/Monitor. Monitor for decreased vitamin K antagonist effects (eg, decreased INR, thrombosis) when combined with metformin. Additionally, consider increased monitoring for hypoglycemia with this combination. Competitive inhibition of CYP2C9-mediated metabolism may also contribute to mechanism.

• cilostazol

  cilostazol, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• ciprofloxacin

  ciprofloxacin increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• citalopram

  citalopram, warfarin. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Serotonin release by platelets plays an important role in hemostasis. SSRIs and SNRIs may increase anticoagulation effect of warfarin. .

• clarithromycin

  clarithromycin will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• clopidogrel

  clopidogrel, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• cobicistat

  cobicistat will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• coenzyme Q10

  coenzyme Q10, warfarin. unspecified interaction mechanism. Use Caution/Monitor. The data from studies and case reports is conflicting.

• colesevelam

  colesevelam increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• conivaptan

  conivaptan will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• dabrafenib

  dabrafenib will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.
  
  dabrafenib will decrease the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inducers of these isoenzymes and adjust warfarin dose if needed.

• darunavir

  darunavir, warfarin. Other (see comment). Use Caution/Monitor. Comment: Warfarin serum concentrations may be increased or decreased. Darunavir may increase levels the less potent R-enantiomer of warfarin, but is used in combination with ritonavir which may decrease R-warfarin levels. .

• dasatinib

  dasatinib increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• delafloxacin

  delafloxacin increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• delavirdine

  delavirdine will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• demeclocycline

  demeclocycline increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• deoxycholic acid

  deoxycholic acid increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• desogestrel

  desogestrel increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• desvenlafaxine

  desvenlafaxine, warfarin. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Serotonin release by platelets plays an important role in hemostasis. SSRIs and SNRIs may increase anticoagulation effect of warfarin. .

• diclofenac

  diclofenac, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• dienogest/estradiol valerate

  dienogest/estradiol valerate increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• diflunisal

  diflunisal, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• dipyridamole

  dipyridamole, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• doxycycline

  doxycycline increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• dronedarone

  dronedarone increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• drospirenone

  drospirenone increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• duloxetine

  duloxetine, warfarin. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Serotonin release by platelets plays an important role in hemostasis. SSRIs and SNRIs may increase anticoagulation effect of warfarin. .

• econazole topical

  econazole topical will increase the level or effect of warfarin by anticoagulation. Use Caution/Monitor. Most cases reported product application with use under occlusion, genital application, or application to a large body surface area which may increase systemic absorption; monitor International Normalized Ratio (INR) and/or prothrombin time, especially for patients who apply to large body surface areas, in the genital area, or under occlusion

• efavirenz

  efavirenz will decrease the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inducers of these isoenzymes and adjust warfarin dose if needed.

• elagolix

  elagolix will decrease the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inducers of these isoenzymes and adjust warfarin dose if needed.

• elranatamab

  elranatamab will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor. Elranatamab causes cytokine release syndrome (CRS) that may suppress activity of CYP enzymes, resulting in increased exposure of CYP substrates. This is more likely to occur from initiation of elranatamab step-up dosing up to 14 days after the first treatment dose and during and after CRS.

• elvitegravir

  elvitegravir will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• encorafenib

  encorafenib, warfarin. affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Warfarin serum concentrations may be increased or decreased. Encorafenib it both an inhibitor and inducer of CYP3A4. The less potent R-enantiomer of warfarin is a substrate of CYP3A4.

• entacapone

  entacapone increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• enzalutamide

  enzalutamide will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• epcoritamab

  epcoritamab, warfarin. affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor. Epcoritamab causes release of cytokines that may suppress activity of CYP enzymes, resulting in increased exposure of CYP substrates. For certain CYP substrates, minimal changes in their concentration may lead to serious adverse reactions. If needed, modify therapy as recommended in the substrate's prescribing information. .

• epoprostenol

  epoprostenol, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• eptifibatide

  eptifibatide, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• eravacycline

  eravacycline increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• escitalopram

  escitalopram, warfarin. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Serotonin release by platelets plays an important role in hemostasis. SSRIs and SNRIs may increase anticoagulation effect of warfarin. .

• eslicarbazepine acetate

  eslicarbazepine acetate will decrease the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inducers of these isoenzymes and adjust warfarin dose if needed.

• estradiol

  estradiol increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• ethacrynic acid

  ethacrynic acid increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• etodolac

  etodolac, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• etoposide

  etoposide increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• etravirine

  etravirine will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.
  
  etravirine will decrease the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inducers of these isoenzymes and adjust warfarin dose if needed.

• exenatide injectable solution

  exenatide injectable solution increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• exenatide injectable suspension

  exenatide injectable suspension increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• exenatide subdermal implant

  exenatide subdermal implant increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• fenofibrate

  fenofibrate will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely. Mechanism of interaction may be caused by CYP2C9 inhibition and protein-binding displacement.

• fenofibrate micronized

  fenofibrate micronized will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely. Mechanism of interaction may be caused by CYP2C9 inhibition and protein-binding displacement.

• fenofibric acid

  fenofibric acid will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely. Mechanism of interaction may be caused by CYP2C9 inhibition and protein-binding displacement.

• fenoprofen

  fenoprofen, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• fexinidazole

  fexinidazole will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• fluconazole

  fluconazole will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely. If coadministered, consider decreasing warfarin dose by 10-20%.

• fludrocortisone

  fludrocortisone increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• fluorouracil

  fluorouracil will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• fluoxetine

  fluoxetine, warfarin. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Serotonin release by platelets plays an important role in hemostasis. SSRIs and SNRIs may increase anticoagulation effect of warfarin. .

• flurbiprofen

  flurbiprofen will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.
  
  flurbiprofen, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• fluvastatin

  fluvastatin will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.
  
  fluvastatin increases effects of warfarin by anticoagulation. Use Caution/Monitor. Dosage adjustment of anticoagulant based in INR and clinical response may be necessary.

• fluvoxamine

  fluvoxamine, warfarin. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Serotonin release by platelets plays an important role in hemostasis. SSRIs and SNRIs may increase anticoagulation effect of warfarin. .

• fosamprenavir

  fosamprenavir will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• fosaprepitant

  fosaprepitant will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely. In patients on chronic warfarin therapy, monitor INR in the 2-week period, particularly at 7-10 days, following aprepitant or fosaprepitant administration with each chemotherapy cycle

• fosphenytoin

  fosphenytoin will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• fruquintinib

  fruquintinib, warfarin. Other (see comment). Use Caution/Monitor. Comment: Fruquintinib may cause serious hemorrhagic events. Monitor INR in patients receiving anticoagulants.

• gefitinib

  gefitinib increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• gemcitabine

  gemcitabine increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• gemfibrozil

  gemfibrozil will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely. If coadministered, consider decreasing warfarin dose by one-fourth to one-third.

• gemifloxacin

  gemifloxacin increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• givosiran

  givosiran will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• glimepiride

  glimepiride, warfarin. Either increases effects of the other by receptor binding competition. Use Caution/Monitor. Monitor for decreased vitamin K antagonist effects (eg, decreased INR, thrombosis) when combined with metformin. Additionally, consider increased monitoring for hypoglycemia with this combination. Competitive inhibition of CYP2C9-mediated metabolism may also contribute to mechanism.

• glipizide

  glipizide, warfarin. Either increases effects of the other by receptor binding competition. Use Caution/Monitor. Monitor for decreased vitamin K antagonist effects (eg, decreased INR, thrombosis) when combined with metformin. Additionally, consider increased monitoring for hypoglycemia with this combination. Competitive inhibition of CYP2C9-mediated metabolism may also contribute to mechanism.

• glofitamab

  glofitamab, warfarin. affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor. Glofitamab causes release of cytokines that may suppress activity of CYP enzymes, resulting in increased exposure of CYP substrates. For certain CYP substrates, minimal changes in their concentration may lead to serious adverse reactions. If needed, modify therapy as recommended in the substrate's prescribing information. .

• glucagon

  glucagon increases effects of warfarin by Other (see comment). Use Caution/Monitor. Comment: Effect observed only when doses exceed 50 mg administered over a 2 day period.

• glyburide

  glyburide, warfarin. Either increases effects of the other by receptor binding competition. Use Caution/Monitor. Monitor for decreased vitamin K antagonist effects (eg, decreased INR, thrombosis) when combined with metformin. Additionally, consider increased monitoring for hypoglycemia with this combination. Competitive inhibition of CYP2C9-mediated metabolism may also contribute to mechanism.

• griseofulvin

  griseofulvin will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• hydrocortisone

  hydrocortisone increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• ibritumomab tiuxetan

  ibritumomab tiuxetan increases effects of warfarin by anticoagulation. Use Caution/Monitor.

• ibrutinib

  ibrutinib, warfarin. Either increases effects of the other by anticoagulation. Use Caution/Monitor. Ibrutinib may potentiate the effects of anticoagulant agents such as warfarin may increase the risk of bleeding; monitor for signs of bleeding.
  
  warfarin, ibrutinib. Either increases effects of the other by anticoagulation. Use Caution/Monitor. Ibrutinib may potentiate the effects of anticoagulant agents such as warfarin may increase the risk of bleeding; monitor for signs of bleeding.

• ibuprofen

  ibuprofen, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• ibuprofen IV

  ibuprofen IV, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• icosapent

  icosapent increases effects of warfarin by anticoagulation. Use Caution/Monitor.

• idelalisib

  idelalisib will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• iloprost

  iloprost, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• indinavir

  indinavir will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• indomethacin

  indomethacin, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• inotersen

  inotersen increases effects of warfarin by anticoagulation. Use Caution/Monitor.

• interferon alfa 2b

  interferon alfa 2b increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• interferon alfa n3

  interferon alfa n3 increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• isoniazid

  isoniazid will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• itraconazole

  itraconazole will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• ivermectin

  ivermectin increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• ivosidenib

  ivosidenib will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• kanamycin

  kanamycin increases effects of warfarin by anticoagulation. Use Caution/Monitor.

• ketoconazole

  ketoconazole will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• ketoprofen

  ketoprofen, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• ketorolac

  ketorolac, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• lactulose

  lactulose increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• leflunomide

  leflunomide increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• levocarnitine

  levocarnitine increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• levofloxacin

  levofloxacin increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• levomilnacipran

  levomilnacipran, warfarin. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Serotonin release by platelets plays an important role in hemostasis. SSRIs and SNRIs may increase anticoagulation effect of warfarin. .

• levonorgestrel oral/ethinylestradiol/ferrous bisglycinate

  levonorgestrel oral/ethinylestradiol/ferrous bisglycinate increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• levonorgestrel transdermal

  levonorgestrel transdermal increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• levothyroxine

  levothyroxine increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• liothyronine

  liothyronine increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• liotrix

  liotrix increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• lonafarnib

  lonafarnib will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• lonapegsomatropin

  lonapegsomatropin will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor. Limited published data indicate that growth hormone treatment increases cytochrome P450 (CYP450)-mediated antipyrine clearance. Caution with sensitive CYP substrates

• lopinavir

  lopinavir will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• lorlatinib

  lorlatinib will decrease the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inducers of these isoenzymes and adjust warfarin dose if needed.

• losartan

  losartan will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.

• lovastatin

  lovastatin increases effects of warfarin by anticoagulation. Use Caution/Monitor. Dosage adjustment of anticoagulant based in INR and clinical response may be necessary.

• lumacaftor/ivacaftor

  lumacaftor/ivacaftor will decrease the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inducers of these isoenzymes and adjust warfarin dose if needed.

• meclofenamate

  meclofenamate, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• mefenamic acid

  mefenamic acid, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• mefloquine

  mefloquine increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• megestrol

  megestrol increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• meloxicam

  meloxicam, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• mesalamine

  mesalamine increases effects of warfarin by anticoagulation. Use Caution/Monitor.

• methimazole

  methimazole decreases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• methotrexate

  methotrexate increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• methoxsalen

  methoxsalen will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• methylphenidate

  methylphenidate increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• methylphenidate transdermal

  methylphenidate transdermal will increase the level or effect of warfarin by decreasing metabolism. Modify Therapy/Monitor Closely. Decreasing the dose of these drugs may be required when given coadministered with methylphenidate. Consider monitoring plasma drug concentrations (or INR with coumadin), when initiating or discontinuing methylphenidate.

• methylprednisolone

  methylprednisolone increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• metronidazole

  metronidazole increases levels of warfarin by unspecified interaction mechanism. Use Caution/Monitor. Metronidazole may potentiate the anticoagulant effect of warfarin and other oral coumarin anticoagulants, resulting in a prolongation of prothrombin time. .

• mexiletine

  mexiletine will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• mibefradil

  mibefradil will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• miconazole oral

  miconazole oral will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• milnacipran

  milnacipran, warfarin. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Serotonin release by platelets plays an important role in hemostasis. SSRIs and SNRIs may increase anticoagulation effect of warfarin. .

• minocycline

  minocycline increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• mitapivat

  mitapivat will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• mitotane

  mitotane will decrease the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inducers of these isoenzymes and adjust warfarin dose if needed.

• mobocertinib

  mobocertinib will decrease the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inducers of these isoenzymes and adjust warfarin dose if needed.

• modafinil

  modafinil will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• moxifloxacin

  moxifloxacin increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• nabumetone

  nabumetone, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• nafcillin

  nafcillin will decrease the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inducers of these isoenzymes and adjust warfarin dose if needed.

• naproxen

  naproxen, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• nefazodone

  nefazodone will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• nelfinavir

  nelfinavir will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• neomycin PO

  neomycin PO increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• nifedipine

  nifedipine will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• nintedanib

  nintedanib increases effects of warfarin by anticoagulation. Use Caution/Monitor.

• nirmatrelvir/ritonavir

  nirmatrelvir/ritonavir will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor. INR may increase or decrease. Closely monitor INR if nirmatrelvir/ritonavir is coadministered with warfarin.

• nitisinone

  nitisinone will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.

• norgestimate

  norgestimate increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• obinutuzumab

  obinutuzumab increases effects of warfarin by anticoagulation. Use Caution/Monitor.

• ofloxacin

  ofloxacin increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• olsalazine

  olsalazine increases effects of warfarin by anticoagulation. Use Caution/Monitor.

• omadacycline

  omadacycline increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• omaveloxolone

  omaveloxolone will decrease the level or effect of warfarin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Omaveloxolone may reduce systemic exposure of sensitive CYP3A4 substrates. Check prescribing information of substrate if dosage modification is needed.

• omega 3 fatty acids

  omega 3 fatty acids increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• omeprazole

  omeprazole will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• orlistat

  orlistat increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• oxaprozin

  oxaprozin, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• paroxetine

  paroxetine, warfarin. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Serotonin release by platelets plays an important role in hemostasis. SSRIs and SNRIs may increase anticoagulation effect of warfarin. .

• peginterferon alfa 2a

  peginterferon alfa 2a increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• peginterferon alfa 2b

  peginterferon alfa 2b increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• pentobarbital

  pentobarbital will decrease the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inducers of these isoenzymes and adjust warfarin dose if needed.

• pentosan polysulfate sodium

  pentosan polysulfate sodium increases effects of warfarin by anticoagulation. Use Caution/Monitor.

• pentoxifylline

  pentoxifylline increases effects of warfarin by anticoagulation. Use Caution/Monitor.

• pexidartinib

  pexidartinib will decrease the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inducers of these isoenzymes and adjust warfarin dose if needed.

• phenobarbital

  phenobarbital will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• phenytoin

  phenytoin will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• piperacillin

  piperacillin, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Platelet dysfunction occurs with extended-spectrum penicillins in varying degrees. Monitor INR and adjust warfarin dose if needed.

• piroxicam

  piroxicam, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• pirtobrutinib

  pirtobrutinib will increase the level or effect of warfarin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Pirtobrutinib (a CYP3A4 inhibitor) may increase plasma concentrations of sensitive CYP3A4 substrate which may increase the risk of adverse reactions related to these substrates.

• posaconazole

  posaconazole will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• potassium iodide

  potassium iodide decreases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• prasugrel

  prasugrel, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• pravastatin

  pravastatin increases effects of warfarin by anticoagulation. Use Caution/Monitor. Dosage adjustment of anticoagulant based in INR and clinical response may be necessary.

• prednisolone

  prednisolone increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• prednisone

  prednisone increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• primaquine

  primaquine will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• primidone

  primidone will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• propofol

  propofol will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• propylthiouracil

  propylthiouracil decreases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• quinidine

  quinidine will increase the level or effect of warfarin by decreasing metabolism. Use Caution/Monitor. Cinchona alkaloids, including quinine and quinidine, may increase anticoagulant effect of vitamin K antagonists by inhibiting hepatic synthesis of vitamin K-dependent coagulation proteins.

• quinine

  quinine will increase the level or effect of warfarin by decreasing metabolism. Use Caution/Monitor. Cinchona alkaloids, including quinine and quinidine, may increase anticoagulant effect of vitamin K antagonists by inhibiting hepatic synthesis of vitamin K-dependent coagulation proteins.

• regorafenib

  regorafenib increases effects of warfarin by anticoagulation. Use Caution/Monitor.

• remdesivir

  remdesivir increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• reteplase

  reteplase increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• rifampin

  rifampin will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• rifapentine

  rifapentine will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• ritlecitinib

  ritlecitinib will increase the level or effect of warfarin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Ritlecitinib inhibits CYP3A4 substrates; coadministration increases AUC and peak plasma concentration sensitive substrates, which may increase risk of adverse reactions. Additional monitoring and dosage adjustment may be needed in accordance with product labeling of CYP3A substrates.

• ritonavir

  ritonavir will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• romidepsin

  romidepsin increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• ropeginterferon alfa 2b

  ropeginterferon alfa 2b increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• rosuvastatin

  rosuvastatin increases effects of warfarin by anticoagulation. Use Caution/Monitor.

• rucaparib

  rucaparib will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely. Rucaparib inhibits CYP1A2, CYP3A (the less potent warfarin R-enantiomer is a substrates of these). Also inhibits CYP2C9, of which the more potent warfarin S-enantiomer is a substrate.

• saquinavir

  saquinavir will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• secobarbital

  secobarbital will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• segesterone/ethinyl estradiol

  segesterone/ethinyl estradiol increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• sertraline

  sertraline, warfarin. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Serotonin release by platelets plays an important role in hemostasis. SSRIs and SNRIs may increase anticoagulation effect of warfarin. .

• simvastatin

  simvastatin increases effects of warfarin by anticoagulation. Use Caution/Monitor.

• somapacitan

  somapacitan will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor. Limited published data indicate that growth hormone treatment increases cytochrome P450 (CYP450)-mediated antipyrine clearance. Caution with sensitive CYP substrates

• somatrogon

  somatrogon will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor. Limited published data indicate that growth hormone treatment increases cytochrome P450 (CYP450)-mediated antipyrine clearance. Caution with sensitive CYP substrates

• somatropin

  somatropin will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor. Limited published data indicate that growth hormone treatment increases cytochrome P450 (CYP450)-mediated antipyrine clearance. Caution with sensitive CYP substrates

• sorafenib

  sorafenib will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.

• sotorasib

  sotorasib will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• sparsentan

  sparsentan will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor. Sparsentan (a CYP2C9 inducer) decreases exposure of CYP2C9 substrates and reduces efficacy related to these substrates.

• St John's Wort

  St John's Wort will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• sulfadiazine

  sulfadiazine will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely. Mechanism of interaction may be caused by CYP2C9 inhibition and protein-binding displacement. If coadministered, consider decreasing warfarin dose by 10-20%.

• sulfamethoxazole

  sulfamethoxazole will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely. Mechanism of interaction may be caused by CYP2C9 inhibition and protein-binding displacement. If coadministered, consider decreasing warfarin dose by 10-20%.

• sulfasalazine

  sulfasalazine increases effects of warfarin by anticoagulation. Use Caution/Monitor.

• sulindac

  sulindac, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• talquetamab

  talquetamab will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor. Talquetamab causes cytokine release syndrome (CRS) that may suppress activity of CYP enzymes, resulting in increased exposure of CYP substrates. This is more likely to occur from initiation of talquetamab step-up dosing up to 14 days after the first treatment dose and during and after CRS.

• teclistamab

  teclistamab will increase the level or effect of warfarin by altering metabolism. Use Caution/Monitor. Teclistamab causes release of cytokines that may suppress activity of CYP450 enzymes, resulting in increased exposure of CYP substrates. Monitor for increased concentrations or toxicities of sensitive CYP substrates. Adjust dose of CYP substrate drug as needed.

• telavancin

  telavancin increases effects of warfarin by anticoagulation. Use Caution/Monitor.

• tenecteplase

  tenecteplase increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• tetracycline

  tetracycline increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• thyroid desiccated

  thyroid desiccated increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• ticagrelor

  ticagrelor, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• ticarcillin

  ticarcillin, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Platelet dysfunction occurs with extended-spectrum penicillins in varying degrees. Monitor INR and adjust warfarin dose if needed.

• ticlopidine

  ticlopidine, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.
  
  ticlopidine will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• tipranavir

  tipranavir will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• tirofiban

  tirofiban, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• tolazamide

  tolazamide, warfarin. Either increases effects of the other by receptor binding competition. Use Caution/Monitor. Monitor for decreased vitamin K antagonist effects (eg, decreased INR, thrombosis) when combined with metformin. Additionally, consider increased monitoring for hypoglycemia with this combination. Competitive inhibition of CYP2C9-mediated metabolism may also contribute to mechanism.

• tolbutamide

  tolbutamide, warfarin. Either increases effects of the other by receptor binding competition. Use Caution/Monitor. Monitor for decreased vitamin K antagonist effects (eg, decreased INR, thrombosis) when combined with metformin. Additionally, consider increased monitoring for hypoglycemia with this combination. Competitive inhibition of CYP2C9-mediated metabolism may also contribute to mechanism.

• tolmetin

  tolmetin, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• toremifene

  toremifene increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• tranylcypromine

  tranylcypromine will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• triamcinolone acetonide extended-release injectable suspension

  triamcinolone acetonide extended-release injectable suspension increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• triamcinolone acetonide injectable suspension

  triamcinolone acetonide injectable suspension increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• trofinetide

  trofinetide will increase the level or effect of warfarin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Monitor CYP3A4 substrates for which a small increase in plasma concentration may lead to serious toxicities if coadministered with trofinetide (a weak CYP3A4 inhibitor).

• venlafaxine

  venlafaxine, warfarin. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Serotonin release by platelets plays an important role in hemostasis. SSRIs and SNRIs may increase anticoagulation effect of warfarin. .

• vilazodone

  vilazodone, warfarin. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Serotonin release by platelets plays an important role in hemostasis. SSRIs and SNRIs may increase anticoagulation effect of warfarin. .

• vitamin A

  vitamin A increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• vitamin E

  vitamin E increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• vitamin K1 (phytonadione)

  vitamin K1 (phytonadione), warfarin. Either decreases effects of the other by anticoagulation. Use Caution/Monitor. Monitor INR with corresponding increases or decreases in vitamin K intake significantly affecting vitamin k blood levels.

• voriconazole

  voriconazole will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• vortioxetine

  vortioxetine, warfarin. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Serotonin release by platelets plays an important role in hemostasis. SSRIs and SNRIs may increase anticoagulation effect of warfarin. .

• zafirlukast

  zafirlukast will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.

• zanubrutinib

  zanubrutinib increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• zileuton

  zileuton will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

Minor (5)

• acetazolamide

  warfarin will decrease the level or effect of acetazolamide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• anastrozole

  warfarin will decrease the level or effect of anastrozole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• ceritinib

  warfarin will decrease the level or effect of ceritinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• cyclophosphamide

  warfarin will decrease the level or effect of cyclophosphamide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• larotrectinib

  warfarin will decrease the level or effect of larotrectinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• abciximab

  Monitor Closely (1)abciximab, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• acalabrutinib

  Monitor Closely (1)acalabrutinib increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• acetaminophen

  Monitor Closely (1)acetaminophen increases effects of warfarin by anticoagulation. Use Caution/Monitor.

• acetaminophen IV

  Monitor Closely (1)acetaminophen IV increases effects of warfarin by anticoagulation. Use Caution/Monitor. Likely to occur at doses exceedin 1.3-2 g/day for multiple consecutive days.

• acetaminophen rectal

  Monitor Closely (1)acetaminophen rectal increases effects of warfarin by anticoagulation. Use Caution/Monitor. Likely to occur at doses exceedin 1.3-2 g/day for multiple consecutive days.

• acetaminophen/pamabrom

  Monitor Closely (1)acetaminophen/pamabrom increases effects of warfarin by anticoagulation. Use Caution/Monitor. Likely to occur at doses exceedin 1.3-2 g/day acetaminophen for multiple consecutive days.

• acetaminophen/phenyltoloxamine

  Monitor Closely (1)acetaminophen/phenyltoloxamine increases effects of warfarin by anticoagulation. Use Caution/Monitor. Likely to occur at doses exceedin 1.3-2 g/day acetaminophen for multiple consecutive days.

• acetazolamide

  Minor (1)warfarin will decrease the level or effect of acetazolamide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• adagrasib

  Serious - Use Alternative (1)adagrasib will increase the level or effect of warfarin by Other (see comment). Avoid or Use Alternate Drug. Avoid coadministration of adagrasib, a CYP3A4 and CYP2C9 inhibitor, with warfarin, a sensitive CYP3A and CYP2C9 substrate, unless otherwise recommended in the prescribing information for warfarin.

• allopurinol

  Serious - Use Alternative (1)allopurinol increases effects of warfarin by anticoagulation. Avoid or Use Alternate Drug.

• alpelisib

  Monitor Closely (1)alpelisib will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• aminosalicylic acid

  Monitor Closely (1)aminosalicylic acid increases effects of warfarin by anticoagulation. Use Caution/Monitor.

• amiodarone

  Monitor Closely (1)amiodarone will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely. Coadministration increases INR by 100% after 3-4 days. Reduce warfarin dose by one-third to one-half and monitor INR.

• amitriptyline

  Monitor Closely (1)amitriptyline increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• amobarbital

  Monitor Closely (1)amobarbital will decrease the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inducers of these isoenzymes and adjust warfarin dose if needed.

• anagrelide

  Monitor Closely (1)anagrelide, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• anastrozole

  Minor (1)warfarin will decrease the level or effect of anastrozole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• apalutamide

  Monitor Closely (1)apalutamide will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• apixaban

  Serious - Use Alternative (1)apixaban increases effects of warfarin by anticoagulation. Avoid or Use Alternate Drug. Avoid combined use once INR is established in the desired therapeutic range.

• aprepitant

  Monitor Closely (1)aprepitant will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely. In patients on chronic warfarin therapy, monitor INR in the 2-week period, particularly at 7-10 days, following aprepitant or fosaprepitant administration with each chemotherapy cycle

• argatroban

  Serious - Use Alternative (1)argatroban increases effects of warfarin by anticoagulation. Avoid or Use Alternate Drug. Avoid combined use once INR is established in the desired therapeutic range.

• armodafinil

  Monitor Closely (1)armodafinil will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• asciminib

  Monitor Closely (1)asciminib will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.

• aspirin

  Monitor Closely (1)aspirin increases effects of warfarin by anticoagulation. Modify Therapy/Monitor Closely. Avoid coadministration of chronic high-dose aspirin. Aspirin's antiplatelet properties may increase anticoagulation effect of warfarin. The need for simultaneous use of low-dose aspirin and warfarin is common for patients with cardiovascular disease. .

• atazanavir

  Monitor Closely (1)atazanavir will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• atovaquone

  Monitor Closely (1)atovaquone increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• azathioprine

  Monitor Closely (1)azathioprine decreases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• azithromycin

  Monitor Closely (1)azithromycin increases toxicity of warfarin by anticoagulation. Use Caution/Monitor. Postmarketing reports have suggested that concomitant administration of azithromycin may potentiate effects of oral warfarin but the interaction does not appear to alter prothrombin time.

• balsalazide

  Monitor Closely (1)balsalazide increases effects of warfarin by anticoagulation. Use Caution/Monitor.

• belzutifan

  Monitor Closely (1)belzutifan will decrease the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inducers of these isoenzymes and adjust warfarin dose if needed.

• benzhydrocodone/acetaminophen

  Monitor Closely (1)benzhydrocodone/acetaminophen increases effects of warfarin by anticoagulation. Use Caution/Monitor. Likely to occur at doses exceedin 1.3-2 g/day acetamionphen for multiple consecutive days.

• betamethasone

  Monitor Closely (1)betamethasone increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• betrixaban

  Serious - Use Alternative (1)betrixaban increases effects of warfarin by anticoagulation. Avoid or Use Alternate Drug. Avoid combined use once INR is established in the desired therapeutic range.

• bexarotene

  Monitor Closely (1)bexarotene will decrease the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inducers of these isoenzymes and adjust warfarin dose if needed.

• bicalutamide

  Monitor Closely (1)bicalutamide increases effects of warfarin by Other (see comment). Use Caution/Monitor. Comment: May increase free concentrations of vitamin K antagonists.

• bismuth subsalicylate

  Serious - Use Alternative (1)bismuth subsalicylate increases effects of warfarin by anticoagulation. Avoid or Use Alternate Drug.

• bivalirudin

  Serious - Use Alternative (1)bivalirudin increases effects of warfarin by anticoagulation. Avoid or Use Alternate Drug. Avoid combined use once INR is established in the desired therapeutic range.

• bosentan

  Monitor Closely (1)bosentan will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• butalbital

  Monitor Closely (1)butalbital will decrease the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inducers of these isoenzymes and adjust warfarin dose if needed.

• cangrelor

  Monitor Closely (1)cangrelor, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• capecitabine

  Monitor Closely (1)capecitabine will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely. Closely monitor INR and PT and adjust dose. Increased INR and PT can occur within a few days of initiating capecitabine.

• carbamazepine

  Monitor Closely (1)carbamazepine will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• cefaclor

  Monitor Closely (1)cefaclor increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• cefadroxil

  Monitor Closely (1)cefadroxil increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• cefazolin

  Monitor Closely (1)cefazolin increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• cefdinir

  Monitor Closely (1)cefdinir increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• cefditoren

  Monitor Closely (1)cefditoren increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• cefepime

  Monitor Closely (1)cefepime increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• cefiderocol

  Monitor Closely (1)cefiderocol increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• cefixime

  Monitor Closely (1)cefixime increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• cefotaxime

  Monitor Closely (1)cefotaxime increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• cefotetan

  Monitor Closely (1)cefotetan increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• cefoxitin

  Monitor Closely (1)cefoxitin increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• cefpodoxime

  Monitor Closely (1)cefpodoxime increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• cefprozil

  Monitor Closely (1)cefprozil increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• ceftaroline

  Monitor Closely (1)ceftaroline increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• ceftazidime

  Monitor Closely (1)ceftazidime increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• ceftibuten

  Monitor Closely (1)ceftibuten increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• ceftolozane/tazobactam

  Monitor Closely (1)ceftolozane/tazobactam increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• ceftriaxone

  Monitor Closely (1)ceftriaxone increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• cefuroxime

  Monitor Closely (1)cefuroxime increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• celecoxib

  Monitor Closely (1)celecoxib increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• cenobamate

  Monitor Closely (1)cenobamate will decrease the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inducers of these isoenzymes and adjust warfarin dose if needed.

• cephalexin

  Monitor Closely (1)cephalexin increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• ceritinib

  Monitor Closely (1)ceritinib will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.Minor (1)warfarin will decrease the level or effect of ceritinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• chenodiol

  Monitor Closely (1)chenodiol increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• chloral hydrate

  Monitor Closely (1)chloral hydrate increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• chloramphenicol

  Monitor Closely (1)chloramphenicol will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• chlorpropamide

  Monitor Closely (1)chlorpropamide, warfarin. Either increases effects of the other by receptor binding competition. Use Caution/Monitor. Monitor for decreased vitamin K antagonist effects (eg, decreased INR, thrombosis) when combined with metformin. Additionally, consider increased monitoring for hypoglycemia with this combination. Competitive inhibition of CYP2C9-mediated metabolism may also contribute to mechanism.

• cholestyramine

  Serious - Use Alternative (1)cholestyramine decreases effects of warfarin by inhibition of GI absorption. Applies only to oral form of both agents. Avoid or Use Alternate Drug. Cholestyramine and vitamin K antagonists should be administered 3-4 hr apart and monitor patients closely for reduced vitamin K antagonist effects.

• choline magnesium trisalicylate

  Serious - Use Alternative (1)choline magnesium trisalicylate increases effects of warfarin by anticoagulation. Avoid or Use Alternate Drug.

• cilostazol

  Monitor Closely (1)cilostazol, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• cimetidine

  Serious - Use Alternative (1)cimetidine increases effects of warfarin by unspecified interaction mechanism. Avoid or Use Alternate Drug.

• ciprofloxacin

  Monitor Closely (1)ciprofloxacin increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• citalopram

  Monitor Closely (1)citalopram, warfarin. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Serotonin release by platelets plays an important role in hemostasis. SSRIs and SNRIs may increase anticoagulation effect of warfarin. .

• clarithromycin

  Monitor Closely (1)clarithromycin will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• clopidogrel

  Monitor Closely (1)clopidogrel, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• cobicistat

  Monitor Closely (1)cobicistat will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• coenzyme Q10

  Monitor Closely (1)coenzyme Q10, warfarin. unspecified interaction mechanism. Use Caution/Monitor. The data from studies and case reports is conflicting.

• colesevelam

  Monitor Closely (1)colesevelam increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• conivaptan

  Monitor Closely (1)conivaptan will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• cyclophosphamide

  Minor (1)warfarin will decrease the level or effect of cyclophosphamide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• dabigatran

  Serious - Use Alternative (1)dabigatran increases effects of warfarin by anticoagulation. Avoid or Use Alternate Drug. Avoid combined use once INR is established in the desired therapeutic range.

• dabrafenib

  Monitor Closely (2)dabrafenib will decrease the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inducers of these isoenzymes and adjust warfarin dose if needed.
  
  dabrafenib will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• danazol

  Serious - Use Alternative (1)danazol increases effects of warfarin by anticoagulation. Avoid or Use Alternate Drug.

• darunavir

  Monitor Closely (1)darunavir, warfarin. Other (see comment). Use Caution/Monitor. Comment: Warfarin serum concentrations may be increased or decreased. Darunavir may increase levels the less potent R-enantiomer of warfarin, but is used in combination with ritonavir which may decrease R-warfarin levels. .

• dasatinib

  Monitor Closely (1)dasatinib increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• defibrotide

  Contraindicated (1)defibrotide, warfarin. Either increases effects of the other by pharmacodynamic synergism. Contraindicated. Defibrotide is contraindicated with systemic anticoagulants. .

• delafloxacin

  Monitor Closely (1)delafloxacin increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• delavirdine

  Monitor Closely (1)delavirdine will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• demeclocycline

  Monitor Closely (1)demeclocycline increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• deoxycholic acid

  Monitor Closely (1)deoxycholic acid increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• desogestrel

  Monitor Closely (1)desogestrel increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• desvenlafaxine

  Monitor Closely (1)desvenlafaxine, warfarin. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Serotonin release by platelets plays an important role in hemostasis. SSRIs and SNRIs may increase anticoagulation effect of warfarin. .

• diclofenac

  Monitor Closely (1)diclofenac, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• dienogest/estradiol valerate

  Monitor Closely (1)dienogest/estradiol valerate increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• diflunisal

  Monitor Closely (1)diflunisal, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• dipyridamole

  Monitor Closely (1)dipyridamole, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• doxycycline

  Monitor Closely (1)doxycycline increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• dronedarone

  Monitor Closely (1)dronedarone increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• drospirenone

  Monitor Closely (1)drospirenone increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• duloxetine

  Monitor Closely (1)duloxetine, warfarin. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Serotonin release by platelets plays an important role in hemostasis. SSRIs and SNRIs may increase anticoagulation effect of warfarin. .

• econazole topical

  Monitor Closely (1)econazole topical will increase the level or effect of warfarin by anticoagulation. Use Caution/Monitor. Most cases reported product application with use under occlusion, genital application, or application to a large body surface area which may increase systemic absorption; monitor International Normalized Ratio (INR) and/or prothrombin time, especially for patients who apply to large body surface areas, in the genital area, or under occlusion

• edoxaban

  Serious - Use Alternative (1)edoxaban increases effects of warfarin by anticoagulation. Avoid or Use Alternate Drug. Avoid combined use once INR is established in the desired therapeutic range.

• efavirenz

  Monitor Closely (1)efavirenz will decrease the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inducers of these isoenzymes and adjust warfarin dose if needed.

• elagolix

  Monitor Closely (1)elagolix will decrease the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inducers of these isoenzymes and adjust warfarin dose if needed.

• elranatamab

  Monitor Closely (1)elranatamab will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor. Elranatamab causes cytokine release syndrome (CRS) that may suppress activity of CYP enzymes, resulting in increased exposure of CYP substrates. This is more likely to occur from initiation of elranatamab step-up dosing up to 14 days after the first treatment dose and during and after CRS.

• elvitegravir

  Monitor Closely (1)elvitegravir will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• encorafenib

  Monitor Closely (1)encorafenib, warfarin. affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Warfarin serum concentrations may be increased or decreased. Encorafenib it both an inhibitor and inducer of CYP3A4. The less potent R-enantiomer of warfarin is a substrate of CYP3A4.

• entacapone

  Monitor Closely (1)entacapone increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• enzalutamide

  Monitor Closely (1)enzalutamide will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• epcoritamab

  Monitor Closely (1)epcoritamab, warfarin. affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor. Epcoritamab causes release of cytokines that may suppress activity of CYP enzymes, resulting in increased exposure of CYP substrates. For certain CYP substrates, minimal changes in their concentration may lead to serious adverse reactions. If needed, modify therapy as recommended in the substrate's prescribing information. .

• epoprostenol

  Monitor Closely (1)epoprostenol, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• eptifibatide

  Monitor Closely (1)eptifibatide, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• eravacycline

  Monitor Closely (1)eravacycline increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• escitalopram

  Monitor Closely (1)escitalopram, warfarin. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Serotonin release by platelets plays an important role in hemostasis. SSRIs and SNRIs may increase anticoagulation effect of warfarin. .

• eslicarbazepine acetate

  Monitor Closely (1)eslicarbazepine acetate will decrease the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inducers of these isoenzymes and adjust warfarin dose if needed.

• estradiol

  Monitor Closely (1)estradiol increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• ethacrynic acid

  Monitor Closely (1)ethacrynic acid increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• etodolac

  Monitor Closely (1)etodolac, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• etoposide

  Monitor Closely (1)etoposide increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• etravirine

  Monitor Closely (2)etravirine will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.
  
  etravirine will decrease the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inducers of these isoenzymes and adjust warfarin dose if needed.

• exenatide injectable solution

  Monitor Closely (1)exenatide injectable solution increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• exenatide injectable suspension

  Monitor Closely (1)exenatide injectable suspension increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• exenatide subdermal implant

  Monitor Closely (1)exenatide subdermal implant increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• fenofibrate

  Monitor Closely (1)fenofibrate will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely. Mechanism of interaction may be caused by CYP2C9 inhibition and protein-binding displacement.

• fenofibrate micronized

  Monitor Closely (1)fenofibrate micronized will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely. Mechanism of interaction may be caused by CYP2C9 inhibition and protein-binding displacement.

• fenofibric acid

  Monitor Closely (1)fenofibric acid will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely. Mechanism of interaction may be caused by CYP2C9 inhibition and protein-binding displacement.

• fenoprofen

  Monitor Closely (1)fenoprofen, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• fexinidazole

  Monitor Closely (1)fexinidazole will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• fluconazole

  Monitor Closely (1)fluconazole will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely. If coadministered, consider decreasing warfarin dose by 10-20%.

• fludrocortisone

  Monitor Closely (1)fludrocortisone increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• fluorouracil

  Monitor Closely (1)fluorouracil will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• fluoxetine

  Monitor Closely (1)fluoxetine, warfarin. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Serotonin release by platelets plays an important role in hemostasis. SSRIs and SNRIs may increase anticoagulation effect of warfarin. .

• fluoxymesterone

  Serious - Use Alternative (1)fluoxymesterone increases effects of warfarin by anticoagulation. Avoid or Use Alternate Drug.

• flurbiprofen

  Monitor Closely (2)flurbiprofen will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.
  
  flurbiprofen, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• fluvastatin

  Monitor Closely (2)fluvastatin will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.
  
  fluvastatin increases effects of warfarin by anticoagulation. Use Caution/Monitor. Dosage adjustment of anticoagulant based in INR and clinical response may be necessary.

• fluvoxamine

  Monitor Closely (1)fluvoxamine, warfarin. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Serotonin release by platelets plays an important role in hemostasis. SSRIs and SNRIs may increase anticoagulation effect of warfarin. .

• fondaparinux

  Serious - Use Alternative (1)fondaparinux increases effects of warfarin by anticoagulation. Avoid or Use Alternate Drug. Avoid combined use once INR is established in the desired therapeutic range.

• fosamprenavir

  Monitor Closely (1)fosamprenavir will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• fosaprepitant

  Monitor Closely (1)fosaprepitant will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely. In patients on chronic warfarin therapy, monitor INR in the 2-week period, particularly at 7-10 days, following aprepitant or fosaprepitant administration with each chemotherapy cycle

• fosphenytoin

  Monitor Closely (1)fosphenytoin will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• fruquintinib

  Monitor Closely (1)fruquintinib, warfarin. Other (see comment). Use Caution/Monitor. Comment: Fruquintinib may cause serious hemorrhagic events. Monitor INR in patients receiving anticoagulants.

• gefitinib

  Monitor Closely (1)gefitinib increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• gemcitabine

  Monitor Closely (1)gemcitabine increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• gemfibrozil

  Monitor Closely (1)gemfibrozil will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely. If coadministered, consider decreasing warfarin dose by one-fourth to one-third.

• gemifloxacin

  Monitor Closely (1)gemifloxacin increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• givosiran

  Monitor Closely (1)givosiran will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• glimepiride

  Monitor Closely (1)glimepiride, warfarin. Either increases effects of the other by receptor binding competition. Use Caution/Monitor. Monitor for decreased vitamin K antagonist effects (eg, decreased INR, thrombosis) when combined with metformin. Additionally, consider increased monitoring for hypoglycemia with this combination. Competitive inhibition of CYP2C9-mediated metabolism may also contribute to mechanism.

• glipizide

  Monitor Closely (1)glipizide, warfarin. Either increases effects of the other by receptor binding competition. Use Caution/Monitor. Monitor for decreased vitamin K antagonist effects (eg, decreased INR, thrombosis) when combined with metformin. Additionally, consider increased monitoring for hypoglycemia with this combination. Competitive inhibition of CYP2C9-mediated metabolism may also contribute to mechanism.

• glofitamab

  Monitor Closely (1)glofitamab, warfarin. affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor. Glofitamab causes release of cytokines that may suppress activity of CYP enzymes, resulting in increased exposure of CYP substrates. For certain CYP substrates, minimal changes in their concentration may lead to serious adverse reactions. If needed, modify therapy as recommended in the substrate's prescribing information. .

• glucagon

  Monitor Closely (1)glucagon increases effects of warfarin by Other (see comment). Use Caution/Monitor. Comment: Effect observed only when doses exceed 50 mg administered over a 2 day period.

• glyburide

  Monitor Closely (1)glyburide, warfarin. Either increases effects of the other by receptor binding competition. Use Caution/Monitor. Monitor for decreased vitamin K antagonist effects (eg, decreased INR, thrombosis) when combined with metformin. Additionally, consider increased monitoring for hypoglycemia with this combination. Competitive inhibition of CYP2C9-mediated metabolism may also contribute to mechanism.

• griseofulvin

  Monitor Closely (1)griseofulvin will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• heparin

  Serious - Use Alternative (1)heparin increases effects of warfarin by anticoagulation. Avoid or Use Alternate Drug. Avoid combined use once INR is established in the desired therapeutic range.

• hydrocortisone

  Monitor Closely (1)hydrocortisone increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• ibritumomab tiuxetan

  Monitor Closely (1)ibritumomab tiuxetan increases effects of warfarin by anticoagulation. Use Caution/Monitor.

• ibrutinib

  Monitor Closely (2)ibrutinib, warfarin. Either increases effects of the other by anticoagulation. Use Caution/Monitor. Ibrutinib may potentiate the effects of anticoagulant agents such as warfarin may increase the risk of bleeding; monitor for signs of bleeding.
  
  warfarin, ibrutinib. Either increases effects of the other by anticoagulation. Use Caution/Monitor. Ibrutinib may potentiate the effects of anticoagulant agents such as warfarin may increase the risk of bleeding; monitor for signs of bleeding.

• ibuprofen

  Monitor Closely (1)ibuprofen, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• ibuprofen IV

  Monitor Closely (1)ibuprofen IV, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• icosapent

  Monitor Closely (1)icosapent increases effects of warfarin by anticoagulation. Use Caution/Monitor.

• idelalisib

  Monitor Closely (1)idelalisib will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• iloprost

  Monitor Closely (1)iloprost, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• indinavir

  Monitor Closely (1)indinavir will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• indomethacin

  Monitor Closely (1)indomethacin, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• inotersen

  Monitor Closely (1)inotersen increases effects of warfarin by anticoagulation. Use Caution/Monitor.

• interferon alfa 2b

  Monitor Closely (1)interferon alfa 2b increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• interferon alfa n3

  Monitor Closely (1)interferon alfa n3 increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• isoniazid

  Monitor Closely (1)isoniazid will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• itraconazole

  Monitor Closely (1)itraconazole will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• ivermectin

  Monitor Closely (1)ivermectin increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• ivosidenib

  Monitor Closely (1)ivosidenib will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• kanamycin

  Monitor Closely (1)kanamycin increases effects of warfarin by anticoagulation. Use Caution/Monitor.

• ketoconazole

  Monitor Closely (1)ketoconazole will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• ketoprofen

  Monitor Closely (1)ketoprofen, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• ketorolac

  Monitor Closely (1)ketorolac, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• lactulose

  Monitor Closely (1)lactulose increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• larotrectinib

  Minor (1)warfarin will decrease the level or effect of larotrectinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• leflunomide

  Monitor Closely (1)leflunomide increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• levocarnitine

  Monitor Closely (1)levocarnitine increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• levofloxacin

  Monitor Closely (1)levofloxacin increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• levomilnacipran

  Monitor Closely (1)levomilnacipran, warfarin. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Serotonin release by platelets plays an important role in hemostasis. SSRIs and SNRIs may increase anticoagulation effect of warfarin. .

• levonorgestrel oral/ethinylestradiol/ferrous bisglycinate

  Monitor Closely (1)levonorgestrel oral/ethinylestradiol/ferrous bisglycinate increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• levonorgestrel transdermal

  Monitor Closely (1)levonorgestrel transdermal increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• levothyroxine

  Monitor Closely (1)levothyroxine increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• liothyronine

  Monitor Closely (1)liothyronine increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• liotrix

  Monitor Closely (1)liotrix increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• lonafarnib

  Monitor Closely (1)lonafarnib will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• lonapegsomatropin

  Monitor Closely (1)lonapegsomatropin will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor. Limited published data indicate that growth hormone treatment increases cytochrome P450 (CYP450)-mediated antipyrine clearance. Caution with sensitive CYP substrates

• lopinavir

  Monitor Closely (1)lopinavir will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• lorlatinib

  Monitor Closely (1)lorlatinib will decrease the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inducers of these isoenzymes and adjust warfarin dose if needed.

• losartan

  Monitor Closely (1)losartan will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.

• lovastatin

  Monitor Closely (1)lovastatin increases effects of warfarin by anticoagulation. Use Caution/Monitor. Dosage adjustment of anticoagulant based in INR and clinical response may be necessary.

• lumacaftor/ivacaftor

  Monitor Closely (1)lumacaftor/ivacaftor will decrease the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inducers of these isoenzymes and adjust warfarin dose if needed.

• magnesium salicylate

  Serious - Use Alternative (1)magnesium salicylate increases effects of warfarin by anticoagulation. Avoid or Use Alternate Drug.

• meclofenamate

  Monitor Closely (1)meclofenamate, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• mefenamic acid

  Monitor Closely (1)mefenamic acid, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• mefloquine

  Monitor Closely (1)mefloquine increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• megestrol

  Monitor Closely (1)megestrol increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• meloxicam

  Monitor Closely (1)meloxicam, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• mesalamine

  Monitor Closely (1)mesalamine increases effects of warfarin by anticoagulation. Use Caution/Monitor.

• methimazole

  Monitor Closely (1)methimazole decreases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• methotrexate

  Monitor Closely (1)methotrexate increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• methoxsalen

  Monitor Closely (1)methoxsalen will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• methylphenidate

  Monitor Closely (1)methylphenidate increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• methylphenidate transdermal

  Monitor Closely (1)methylphenidate transdermal will increase the level or effect of warfarin by decreasing metabolism. Modify Therapy/Monitor Closely. Decreasing the dose of these drugs may be required when given coadministered with methylphenidate. Consider monitoring plasma drug concentrations (or INR with coumadin), when initiating or discontinuing methylphenidate.

• methylprednisolone

  Monitor Closely (1)methylprednisolone increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• methyltestosterone

  Serious - Use Alternative (1)methyltestosterone increases effects of warfarin by anticoagulation. Avoid or Use Alternate Drug.

• metronidazole

  Monitor Closely (1)metronidazole increases levels of warfarin by unspecified interaction mechanism. Use Caution/Monitor. Metronidazole may potentiate the anticoagulant effect of warfarin and other oral coumarin anticoagulants, resulting in a prolongation of prothrombin time. .

• mexiletine

  Monitor Closely (1)mexiletine will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• mibefradil

  Monitor Closely (1)mibefradil will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• miconazole oral

  Monitor Closely (1)miconazole oral will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• mifepristone

  Contraindicated (1)mifepristone increases effects of warfarin by anticoagulation. Contraindicated.

• milnacipran

  Monitor Closely (1)milnacipran, warfarin. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Serotonin release by platelets plays an important role in hemostasis. SSRIs and SNRIs may increase anticoagulation effect of warfarin. .

• minocycline

  Monitor Closely (1)minocycline increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• mitapivat

  Monitor Closely (1)mitapivat will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• mitotane

  Monitor Closely (1)mitotane will decrease the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inducers of these isoenzymes and adjust warfarin dose if needed.

• mobocertinib

  Monitor Closely (1)mobocertinib will decrease the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inducers of these isoenzymes and adjust warfarin dose if needed.

• modafinil

  Monitor Closely (1)modafinil will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• moxifloxacin

  Monitor Closely (1)moxifloxacin increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• nabumetone

  Monitor Closely (1)nabumetone, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• nafcillin

  Monitor Closely (1)nafcillin will decrease the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inducers of these isoenzymes and adjust warfarin dose if needed.

• naproxen

  Monitor Closely (1)naproxen, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• nefazodone

  Monitor Closely (1)nefazodone will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• nelfinavir

  Monitor Closely (1)nelfinavir will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• neomycin PO

  Monitor Closely (1)neomycin PO increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• nifedipine

  Monitor Closely (1)nifedipine will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• nintedanib

  Monitor Closely (1)nintedanib increases effects of warfarin by anticoagulation. Use Caution/Monitor.

• nirmatrelvir/ritonavir

  Monitor Closely (1)nirmatrelvir/ritonavir will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor. INR may increase or decrease. Closely monitor INR if nirmatrelvir/ritonavir is coadministered with warfarin.

• nitisinone

  Monitor Closely (1)nitisinone will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.

• norgestimate

  Monitor Closely (1)norgestimate increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• obinutuzumab

  Monitor Closely (1)obinutuzumab increases effects of warfarin by anticoagulation. Use Caution/Monitor.

• ofloxacin

  Monitor Closely (1)ofloxacin increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• olsalazine

  Monitor Closely (1)olsalazine increases effects of warfarin by anticoagulation. Use Caution/Monitor.

• olutasidenib

  Serious - Use Alternative (1)olutasidenib will decrease the level or effect of warfarin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of olutasidenib (a CYP3A4 inducer) with sensitive CYP3A substrates unless otherwise instructed in substrates prescribing information. If unavoidable, monitor for loss of therapeutic effect of sensitive CYP3A4 substrates.

• omacetaxine

  Contraindicated (1)omacetaxine increases effects of warfarin by anticoagulation. Contraindicated.

• omadacycline

  Monitor Closely (1)omadacycline increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• omaveloxolone

  Monitor Closely (1)omaveloxolone will decrease the level or effect of warfarin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Omaveloxolone may reduce systemic exposure of sensitive CYP3A4 substrates. Check prescribing information of substrate if dosage modification is needed.

• omega 3 fatty acids

  Monitor Closely (1)omega 3 fatty acids increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• omeprazole

  Monitor Closely (1)omeprazole will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• orlistat

  Monitor Closely (1)orlistat increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• oxandrolone

  Serious - Use Alternative (1)oxandrolone increases effects of warfarin by anticoagulation. Avoid or Use Alternate Drug.

• oxaprozin

  Monitor Closely (1)oxaprozin, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• oxymetholone

  Serious - Use Alternative (1)oxymetholone increases effects of warfarin by anticoagulation. Avoid or Use Alternate Drug.

• paroxetine

  Monitor Closely (1)paroxetine, warfarin. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Serotonin release by platelets plays an important role in hemostasis. SSRIs and SNRIs may increase anticoagulation effect of warfarin. .

• peginterferon alfa 2a

  Monitor Closely (1)peginterferon alfa 2a increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• peginterferon alfa 2b

  Monitor Closely (1)peginterferon alfa 2b increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• pentobarbital

  Monitor Closely (1)pentobarbital will decrease the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inducers of these isoenzymes and adjust warfarin dose if needed.

• pentosan polysulfate sodium

  Monitor Closely (1)pentosan polysulfate sodium increases effects of warfarin by anticoagulation. Use Caution/Monitor.

• pentoxifylline

  Monitor Closely (1)pentoxifylline increases effects of warfarin by anticoagulation. Use Caution/Monitor.

• pexidartinib

  Monitor Closely (1)pexidartinib will decrease the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inducers of these isoenzymes and adjust warfarin dose if needed.

• phenobarbital

  Monitor Closely (1)phenobarbital will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• phenytoin

  Monitor Closely (1)phenytoin will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• piperacillin

  Monitor Closely (1)piperacillin, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Platelet dysfunction occurs with extended-spectrum penicillins in varying degrees. Monitor INR and adjust warfarin dose if needed.

• piroxicam

  Monitor Closely (1)piroxicam, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• pirtobrutinib

  Monitor Closely (1)pirtobrutinib will increase the level or effect of warfarin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Pirtobrutinib (a CYP3A4 inhibitor) may increase plasma concentrations of sensitive CYP3A4 substrate which may increase the risk of adverse reactions related to these substrates.

• posaconazole

  Monitor Closely (1)posaconazole will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• potassium iodide

  Monitor Closely (1)potassium iodide decreases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• prasugrel

  Monitor Closely (1)prasugrel, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• pravastatin

  Monitor Closely (1)pravastatin increases effects of warfarin by anticoagulation. Use Caution/Monitor. Dosage adjustment of anticoagulant based in INR and clinical response may be necessary.

• prednisolone

  Monitor Closely (1)prednisolone increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• prednisone

  Monitor Closely (1)prednisone increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• primaquine

  Monitor Closely (1)primaquine will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• primidone

  Monitor Closely (1)primidone will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• propofol

  Monitor Closely (1)propofol will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• propylthiouracil

  Monitor Closely (1)propylthiouracil decreases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• quinidine

  Monitor Closely (1)quinidine will increase the level or effect of warfarin by decreasing metabolism. Use Caution/Monitor. Cinchona alkaloids, including quinine and quinidine, may increase anticoagulant effect of vitamin K antagonists by inhibiting hepatic synthesis of vitamin K-dependent coagulation proteins.

• quinine

  Monitor Closely (1)quinine will increase the level or effect of warfarin by decreasing metabolism. Use Caution/Monitor. Cinchona alkaloids, including quinine and quinidine, may increase anticoagulant effect of vitamin K antagonists by inhibiting hepatic synthesis of vitamin K-dependent coagulation proteins.

• regorafenib

  Monitor Closely (1)regorafenib increases effects of warfarin by anticoagulation. Use Caution/Monitor.

• remdesivir

  Monitor Closely (1)remdesivir increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• reteplase

  Monitor Closely (1)reteplase increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• rifampin

  Monitor Closely (1)rifampin will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• rifapentine

  Monitor Closely (1)rifapentine will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• ritlecitinib

  Monitor Closely (1)ritlecitinib will increase the level or effect of warfarin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Ritlecitinib inhibits CYP3A4 substrates; coadministration increases AUC and peak plasma concentration sensitive substrates, which may increase risk of adverse reactions. Additional monitoring and dosage adjustment may be needed in accordance with product labeling of CYP3A substrates.

• ritonavir

  Monitor Closely (1)ritonavir will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• rivaroxaban

  Serious - Use Alternative (1)rivaroxaban increases effects of warfarin by anticoagulation. Avoid or Use Alternate Drug. Avoid combined use once INR is established in the desired therapeutic range.

• romidepsin

  Monitor Closely (1)romidepsin increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• ropeginterferon alfa 2b

  Monitor Closely (1)ropeginterferon alfa 2b increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• rosuvastatin

  Monitor Closely (1)rosuvastatin increases effects of warfarin by anticoagulation. Use Caution/Monitor.

• rucaparib

  Monitor Closely (1)rucaparib will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely. Rucaparib inhibits CYP1A2, CYP3A (the less potent warfarin R-enantiomer is a substrates of these). Also inhibits CYP2C9, of which the more potent warfarin S-enantiomer is a substrate.

• saquinavir

  Monitor Closely (1)saquinavir will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• secobarbital

  Monitor Closely (1)secobarbital will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• segesterone/ethinyl estradiol

  Monitor Closely (1)segesterone/ethinyl estradiol increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• sertraline

  Monitor Closely (1)sertraline, warfarin. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Serotonin release by platelets plays an important role in hemostasis. SSRIs and SNRIs may increase anticoagulation effect of warfarin. .

• simvastatin

  Monitor Closely (1)simvastatin increases effects of warfarin by anticoagulation. Use Caution/Monitor.

• somapacitan

  Monitor Closely (1)somapacitan will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor. Limited published data indicate that growth hormone treatment increases cytochrome P450 (CYP450)-mediated antipyrine clearance. Caution with sensitive CYP substrates

• somatrogon

  Monitor Closely (1)somatrogon will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor. Limited published data indicate that growth hormone treatment increases cytochrome P450 (CYP450)-mediated antipyrine clearance. Caution with sensitive CYP substrates

• somatropin

  Monitor Closely (1)somatropin will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor. Limited published data indicate that growth hormone treatment increases cytochrome P450 (CYP450)-mediated antipyrine clearance. Caution with sensitive CYP substrates

• sorafenib

  Monitor Closely (1)sorafenib will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.

• sotorasib

  Monitor Closely (1)sotorasib will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• sparsentan

  Monitor Closely (1)sparsentan will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor. Sparsentan (a CYP2C9 inducer) decreases exposure of CYP2C9 substrates and reduces efficacy related to these substrates.

• St John's Wort

  Monitor Closely (1)St John's Wort will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• sulfadiazine

  Monitor Closely (1)sulfadiazine will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely. Mechanism of interaction may be caused by CYP2C9 inhibition and protein-binding displacement. If coadministered, consider decreasing warfarin dose by 10-20%.

• sulfamethoxazole

  Monitor Closely (1)sulfamethoxazole will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely. Mechanism of interaction may be caused by CYP2C9 inhibition and protein-binding displacement. If coadministered, consider decreasing warfarin dose by 10-20%.

• sulfasalazine

  Monitor Closely (1)sulfasalazine increases effects of warfarin by anticoagulation. Use Caution/Monitor.

• sulindac

  Monitor Closely (1)sulindac, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• talquetamab

  Monitor Closely (1)talquetamab will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor. Talquetamab causes cytokine release syndrome (CRS) that may suppress activity of CYP enzymes, resulting in increased exposure of CYP substrates. This is more likely to occur from initiation of talquetamab step-up dosing up to 14 days after the first treatment dose and during and after CRS.

• teclistamab

  Monitor Closely (1)teclistamab will increase the level or effect of warfarin by altering metabolism. Use Caution/Monitor. Teclistamab causes release of cytokines that may suppress activity of CYP450 enzymes, resulting in increased exposure of CYP substrates. Monitor for increased concentrations or toxicities of sensitive CYP substrates. Adjust dose of CYP substrate drug as needed.

• telavancin

  Monitor Closely (1)telavancin increases effects of warfarin by anticoagulation. Use Caution/Monitor.

• tenecteplase

  Monitor Closely (1)tenecteplase increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• testosterone

  Serious - Use Alternative (1)testosterone increases effects of warfarin by anticoagulation. Avoid or Use Alternate Drug.

• tetracycline

  Monitor Closely (1)tetracycline increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• thyroid desiccated

  Monitor Closely (1)thyroid desiccated increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• ticagrelor

  Monitor Closely (1)ticagrelor, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• ticarcillin

  Monitor Closely (1)ticarcillin, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Platelet dysfunction occurs with extended-spectrum penicillins in varying degrees. Monitor INR and adjust warfarin dose if needed.

• ticlopidine

  Monitor Closely (2)ticlopidine will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.
  
  ticlopidine, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• tipranavir

  Monitor Closely (1)tipranavir will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• tirofiban

  Monitor Closely (1)tirofiban, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• tolazamide

  Monitor Closely (1)tolazamide, warfarin. Either increases effects of the other by receptor binding competition. Use Caution/Monitor. Monitor for decreased vitamin K antagonist effects (eg, decreased INR, thrombosis) when combined with metformin. Additionally, consider increased monitoring for hypoglycemia with this combination. Competitive inhibition of CYP2C9-mediated metabolism may also contribute to mechanism.

• tolbutamide

  Monitor Closely (1)tolbutamide, warfarin. Either increases effects of the other by receptor binding competition. Use Caution/Monitor. Monitor for decreased vitamin K antagonist effects (eg, decreased INR, thrombosis) when combined with metformin. Additionally, consider increased monitoring for hypoglycemia with this combination. Competitive inhibition of CYP2C9-mediated metabolism may also contribute to mechanism.

• tolmetin

  Monitor Closely (1)tolmetin, warfarin. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Drugs with antiplatelet properties may increase anticoagulation effect of warfarin.

• toremifene

  Monitor Closely (1)toremifene increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• tranylcypromine

  Monitor Closely (1)tranylcypromine will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• triamcinolone acetonide extended-release injectable suspension

  Monitor Closely (1)triamcinolone acetonide extended-release injectable suspension increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• triamcinolone acetonide injectable suspension

  Monitor Closely (1)triamcinolone acetonide injectable suspension increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• trofinetide

  Monitor Closely (1)trofinetide will increase the level or effect of warfarin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Monitor CYP3A4 substrates for which a small increase in plasma concentration may lead to serious toxicities if coadministered with trofinetide (a weak CYP3A4 inhibitor).

• venlafaxine

  Monitor Closely (1)venlafaxine, warfarin. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Serotonin release by platelets plays an important role in hemostasis. SSRIs and SNRIs may increase anticoagulation effect of warfarin. .

• vilazodone

  Monitor Closely (1)vilazodone, warfarin. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Serotonin release by platelets plays an important role in hemostasis. SSRIs and SNRIs may increase anticoagulation effect of warfarin. .

• vitamin A

  Monitor Closely (1)vitamin A increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• vitamin E

  Monitor Closely (1)vitamin E increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• vitamin K1 (phytonadione)

  Monitor Closely (1)vitamin K1 (phytonadione), warfarin. Either decreases effects of the other by anticoagulation. Use Caution/Monitor. Monitor INR with corresponding increases or decreases in vitamin K intake significantly affecting vitamin k blood levels.

• vorapaxar

  Serious - Use Alternative (1)vorapaxar increases effects of warfarin by anticoagulation. Avoid or Use Alternate Drug.

• voriconazole

  Monitor Closely (1)voriconazole will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• vortioxetine

  Monitor Closely (1)vortioxetine, warfarin. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Serotonin release by platelets plays an important role in hemostasis. SSRIs and SNRIs may increase anticoagulation effect of warfarin. .

• zafirlukast

  Monitor Closely (1)zafirlukast will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.

• zanubrutinib

  Monitor Closely (1)zanubrutinib increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.

• zileuton

  Monitor Closely (1)zileuton will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.