warfarin (Rx)

Brand and Other Names:Coumadin, Jantoven
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Dosing & Uses

AdultPediatricGeriatric

Dosage Forms & Strengths

powder for injection

  • 5mg/vial (discontinued)

tablet

  • 1mg
  • 2mg
  • 2.5mg
  • 3mg
  • 4mg
  • 5mg
  • 6mg
  • 7.5mg
  • 10mg

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

Dosage Forms & Strengths

powder for injection

  • 5mg/vial (discontinued)

tablets

  • 1mg
  • 2mg
  • 2.5mg
  • 3mg
  • 4mg
  • 5mg
  • 6mg
  • 7.5mg
  • 10mg

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

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Interactions

Interaction Checker

and warfarin

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            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 (22)

            • 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.

            • 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 (276)

            • 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.

            • 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.

            • 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.

            • 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.

            • fosphenytoin

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

            • 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.

            • 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.

            • 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.

            • 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.

            • 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.

            • 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.

            • 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.

            • 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.

            • 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.

            • 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.

            • 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.

            • 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.

            • 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 (0)

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              Adverse Effects

              Frequency Not Defined

              Cholesterol embolus syndrome

              Intraocular hemorrhage

              Abdominal pain

              Flatulence

              Alopecia

              Rash

              Pruritus

              Taste disturbance

              Tissue necrosis

              Headache

              Lethargy

              Dizziness

              Hematuria

              Anemia

              Hepatitis

              Respiratory tract bleeding

              Hypersensitivity reaction

              Hemorrhage

              Blood dyscrasias

              Fever

              "Purple toe" syndrome

              Increased fracture risk with long-term usage

              Calciphylaxis

              Postmarketing Reports

              Acute kidney injury

              Limb ischemia, necrosis, and gangrene in patients with HIT and HITTS

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              Warnings

              Black Box Warnings

              Warfarin sodium can cause major or fatal bleeding; bleeding is more likely to occur during the starting period and with a higher dose (resulting in a higher INR)

              Risk factors for bleeding include high intensity of anticoagulation (INR greater than 4), age 65 years or older, highly variable INRs, history of gastrointestinal bleeding, hypertension, cerebrovascular disease, serious heart disease, anemia, malignancy, trauma, renal insufficiency, concomitant drugs, and long duration of warfarin therapy

              Regular monitoring of INR should be performed on all treated patients; those at high risk of bleeding may benefit from more frequent INR monitoring, careful dose adjustment to desired INR, and a shorter duration of therapy

              Patients should be instructed about prevention measures to minimize the risk of bleeding and to immediately report any signs or symptoms of bleeding to their physician

              Contraindications

              Pregnancy, except in women with mechanical heart valves

              Hemorrhagic tendencies or blood dyscrasias

              Recent or contemplated CNS or eye surgery or traumatic surgery resulting in large open surfaces

              Bleeding tendencies associated with CNS hemorrhage, cerebral aneurysms, dissecting aorta, pericarditis and pericardial effusions, bacterial endocarditis, and active ulceration or overt bleeding of the GI, GU, or respiratory tract

              Threatened abortion, eclampsia, and preeclampsia

              Unsupervised patients with conditions associated with potential high level of noncompliance (eg, dementia, alcoholism, psychosis)

              Spinal puncture and other diagnostic or therapeutic procedures with potential for uncontrollable bleeding

              Major regional or lumbar block anesthesia

              Known hypersensitivity

              Malignant hypertension

              Cautions

              Lower doses may be warranted in the elderly, debilitated patients, malnutrition, CHF, or liver disease

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

              INR >4.0 appears to provide no additional therapeutic benefit in most patients and is associated with a higher risk of bleeding

              Skin necrosis reported with use; caution in patients at risk for hemorrhage, necrosis, or gangrene

              Heparin-induced thrombocytopenia, DVT (may defer warfarin until thrombin generation is controlled and thrombocytopenia has resolved)

              Genetic tests may be warranted to determine best dose for individual patients; variations in CYP2C9 and VKORC1 genes may modify response

              Advise patients receiving warfarin to carry a notice stating that they are undergoing anticoagulant therapy, to alert medical/emergency personnel

              Use caution in patients with acute infection or active TB or conditions that may alter normal GI flora; antibiotics and fever may change response to warfarin

              May release atheromatous plaque emboli; may experience symptoms depending on site of embolization common organs like pancreas, liver, kidneys, and spleen, which may lead to necrosis or death

              Use caution in patients with prolonged vitamin K insufficiencies

              Thyroid disease may increase warfarin responsiveness

              May impair synthesis of coagulation factors in patients with reduced liver function, regardless of etiology, which in turn may lead to increased warfarin sensitivity

              Use caution in lactation

              Calciphylaxis or calcium uremic arteriolopathy has been reported in patients with and without end-stage renal disease; discontinue warfarin and treat calciphylaxis as appropriate; consider alternative anticoagulant therapy

              Maintain consistent intake of vitamin K-containing foods; high vitamin K consumption may decrease warfarin effect

              In patients with altered glomerular integrity or with history of kidney disease, acute kidney injury may occur with therapy, possibly in relation to episodes of excessive anticoagulation and hematuria; more frequent monitoring of anticoagulation is advised in patients with compromised renal function

              Hepatic impairment may impair synthesis of clotting factors and decrease metabolism of warfarin; conduct more frequent monitoring for bleeding

              Contraindicated in any unsupervised patient with senility; conduct more frequent monitoring for bleeding in elderly patients receiving therapy in any situation

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              Pregnancy & Lactation

              Pregnancy

              Adverse outcomes in pregnancy occur regardless of the health of the mother or the use of medications; estimated background risk of major birth defects and miscarriage for indicated population is unknown

              Exposure during pregnancy causes a recognized pattern of major congenital malformations (warfarin embryopathy and fetotoxicity), fatal fetal hemorrhage, and an increased risk of spontaneous abortion and fetal mortality

              Verify pregnancy status of females of reproductive potential prior to initiating therapy

              Advise females of reproductive potential to use effective contraception during treatment, and for at least 1 month after final dose of warfarin

              Lactation

              Not excreted in breast milk as reported in limited published study (AAP Committee states compatible with nursing); because of potential for serious adverse reactions, including bleeding in breastfed infant, consider developmental and health benefits of breastfeeding along with mother’s clinical need for therapy; monitor breastfeeding infants for bruising or bleeding

              Pregnancy Categories

              A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.

              B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.

              C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.

              D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.

              X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.

              NA: Information not available.

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              Pharmacology

              Mechanism of Action

              Interferes with hepatic synthesis of vitamin K-dependent clotting factors II, VII, IX, and X, as well as proteins C and S; S-warfarin is 4 times more potent than R-warfarin

              Warfarin depletes functional vitamin K reserves, which in turn reduces synthesis of active clotting factors, by competitively inhibiting subunit 1 of the multi-unit vitamin K epoxide reductase complex 1 (VKOR1)

              Absorption

              Onset: 36-48 hr

              Duration: 2-5 days

              Peak plasma time: 1.5-3 days

              Distribution

              Protein bound: 99% (albumin)

              Vd: 0.14 L/kg

              Metabolism

              R-warfarin: Hepatic P450 enzymes CYP1A2, CYP2C19, CYP3A4

              S-warfarin: CYP2C9

              Elimination

              Half-life: 20-60 hr (patient specific)

              Pharmacogenomics

              Metabolized primarily via oxidation in the liver by CYP2C9; exerts its anticoagulant effect by inhibiting the protein VKORC1

              Dose influenced by genetic factors (CYP2C9, VKORC1 genotypes)

              Carriers of CYP2C9*2 and CYP2C9*3 require ~19-33% dose reduction, respectively, per allele compared with persons who carry the *1 allele

              Carriers of the VKORC1 A allele require ~28% dose reduction per allele in their genotype compared with persons who carry none

              Genetic testing laboratories

              • The following companies provide genetic testing for CYP2C9 and VKORC1 variants
              • AutoGenomics (http://www.autogenomics.com)
              • EntroGen (http://www.entrogen.com)
              • Kimball Genetics (http://www.kimballgenetics.com)
              • Nanosphere (http://www.nanosphere.us)
              • Osmetech (http://www.osmetech.com)
              • Specialty Laboratories (http://www.specialtylabs.com)
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              Administration

              IV Incompatibilities

              Solution: D10W, NS (?), LR (?)

              Syringe: Heparin

              Y-site: Aminophylline, NH4Cl (?), bretylium, ceftazidime, dobutamine, ciprofloxacin, cimetidine, esmolol, labetalol, metronidazole, Ringer's, vancomycin (may be compatible at low conc of warfarin), and promazine

              IV Preparation

              Reconstitute in 2.7 mL SWI to obtain 2 mg/mL injectable solution

              Use reconstituted solution within 4 hr; discard unused portion

              IV Administration

              Inject 2 mg/mL solution slowly (over 1-2 min) into a peripheral vein

              IV Storage

              Store at room temp and protect from light

              Do not refrigerate

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              Images

              BRAND FORM. UNIT PRICE PILL IMAGE
              Jantoven oral
              -
              2.5 mg tablet
              Jantoven oral
              -
              10 mg tablet
              Jantoven oral
              -
              7.5 mg tablet
              Jantoven oral
              -
              6 mg tablet
              Jantoven oral
              -
              10 mg tablet
              Jantoven oral
              -
              5 mg tablet
              Jantoven oral
              -
              4 mg tablet
              Jantoven oral
              -
              3 mg tablet
              Jantoven oral
              -
              2 mg tablet
              Jantoven oral
              -
              1 mg tablet
              warfarin oral
              -
              4 mg tablet
              warfarin oral
              -
              4 mg tablet
              warfarin oral
              -
              2.5 mg tablet
              warfarin oral
              -
              5 mg tablet
              warfarin oral
              -
              2 mg tablet
              warfarin oral
              -
              5 mg tablet
              warfarin oral
              -
              5 mg tablet
              warfarin oral
              -
              2.5 mg tablet
              warfarin oral
              -
              1 mg tablet
              warfarin oral
              -
              10 mg tablet
              warfarin oral
              -
              6 mg tablet
              warfarin oral
              -
              6 mg tablet
              warfarin oral
              -
              3 mg tablet
              warfarin oral
              -
              1 mg tablet
              warfarin oral
              -
              2 mg tablet
              warfarin oral
              -
              6 mg tablet
              warfarin oral
              -
              5 mg tablet
              warfarin oral
              -
              4 mg tablet
              warfarin oral
              -
              10 mg tablet
              warfarin oral
              -
              7.5 mg tablet
              warfarin oral
              -
              4 mg tablet
              warfarin oral
              -
              3 mg tablet
              warfarin oral
              -
              2 mg tablet
              warfarin oral
              -
              1 mg tablet
              warfarin oral
              -
              4 mg tablet
              warfarin oral
              -
              7.5 mg tablet
              warfarin oral
              -
              1 mg tablet
              warfarin oral
              -
              10 mg tablet
              warfarin oral
              -
              3 mg tablet
              warfarin oral
              -
              2.5 mg tablet
              warfarin oral
              -
              2 mg tablet
              warfarin oral
              -
              2.5 mg tablet
              warfarin oral
              -
              7.5 mg tablet
              warfarin oral
              -
              3 mg tablet
              warfarin oral
              -
              6 mg tablet
              warfarin oral
              -
              1 mg tablet
              warfarin oral
              -
              7.5 mg tablet
              warfarin oral
              -
              7.5 mg tablet
              warfarin oral
              -
              10 mg tablet
              warfarin oral
              -
              6 mg tablet
              warfarin oral
              -
              2.5 mg tablet
              warfarin oral
              -
              3 mg tablet
              warfarin oral
              -
              2 mg tablet

              Copyright © 2010 First DataBank, Inc.

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              Patient Handout

              Patient Education
              warfarin oral

              WARFARIN - ORAL

              (WARF-uh-rin)

              COMMON BRAND NAME(S): Coumadin, Jantoven

              WARNING: Warfarin can cause very serious (possibly fatal) bleeding. This is more likely to occur when you first start taking this medication or if you take too much warfarin.To decrease your risk for bleeding, your doctor or other health care provider will monitor you closely and check your lab results (INR test) to make sure you are not taking too much warfarin. Keep all medical and laboratory appointments. Tell your doctor right away if you notice any signs of serious bleeding. See also Side Effects section.

              USES: This medication is used to treat blood clots (such as in deep vein thrombosis-DVT or pulmonary embolus-PE) and/or to prevent new clots from forming in your body. Preventing harmful blood clots helps to reduce the risk of a stroke or heart attack. Conditions that increase your risk of developing blood clots include a certain type of irregular heart rhythm (atrial fibrillation), heart valve replacement, recent heart attack, and certain surgeries (such as hip/knee replacement).Warfarin is commonly called a "blood thinner," but the more correct term is "anticoagulant." It helps to keep blood flowing smoothly in your body by decreasing the amount of certain substances (clotting proteins) in your blood.

              HOW TO USE: Read the Medication Guide provided by your pharmacist before you start taking warfarin and each time you get a refill. If you have any questions, ask your doctor or pharmacist.Take this medication by mouth with or without food as directed by your doctor or other health care professional, usually once a day. It is very important to take it exactly as directed. Do not increase the dose, take it more frequently, or stop using it unless directed by your doctor.Dosage is based on your medical condition, laboratory tests (such as INR), and response to treatment. Your doctor or other health care provider will monitor you closely while you are taking this medication to determine the right dose for you.Use this medication regularly to get the most benefit from it. To help you remember, take it at the same time each day.It is important to eat a balanced, consistent diet while taking warfarin. Some foods can affect how warfarin works in your body and may affect your treatment and dose. Avoid sudden large increases or decreases in your intake of foods high in vitamin K (such as broccoli, cauliflower, cabbage, brussels sprouts, kale, spinach, and other green leafy vegetables, liver, green tea, certain vitamin supplements). If you are trying to lose weight, check with your doctor before you try to go on a diet.Since this drug can be absorbed through the skin and lungs and may harm an unborn baby, women who are pregnant or who may become pregnant should not handle this medication or breathe the dust from the tablets.

              SIDE EFFECTS: Nausea, loss of appetite, or stomach/abdominal pain may occur. If any of these effects last or get worse, tell your doctor or pharmacist promptly.Remember that this medication has been prescribed because your doctor has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.This medication can cause serious bleeding if it affects your blood clotting proteins too much (shown by unusually high INR lab results). Even if your doctor stops your medication, this risk of bleeding can continue for up to a week. Tell your doctor right away if you have any signs of serious bleeding, including: nosebleeds that happen often or don't stop, unusual pain/swelling/discomfort, unusual/easy bruising, prolonged bleeding from cuts or gums, unusually heavy/prolonged menstrual flow, pink/dark urine, coughing up blood, vomit that is bloody or looks like coffee grounds, severe headache, dizziness/fainting, unusual tiredness/weakness, bloody/black/tarry stools, chest pain, shortness of breath, difficulty swallowing.Tell your doctor right away if you have any serious side effects, including: nausea/vomiting that doesn't stop, severe stomach/abdominal pain, yellowing eyes/skin.This drug rarely has caused very serious (possibly fatal) problems if its effects lead to small blood clots (usually at the beginning of treatment). This can lead to severe skin/tissue damage that may require surgery or amputation if left untreated. Patients with certain blood conditions (protein C or S deficiency) may be at greater risk. Get medical help right away if any of these rare but serious side effects occur: painful/red/purplish patches on the skin (such as on the toe, breast, abdomen), signs of kidney problems (such as change in the amount of urine), vision changes, confusion, trouble speaking, weakness on one side of the body.A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.In the US -Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

              PRECAUTIONS: Before taking warfarin, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.Before using this medication, tell your doctor or pharmacist your medical history, especially of: blood disorders (such as anemia, hemophilia), bleeding problems (such as bleeding of the stomach/intestines, bleeding in the brain), blood vessel disorders (such as aneurysms), recent major injury/surgery, kidney disease, liver disease, alcohol use, mental/mood disorders (including memory problems), frequent falls/injuries.It is important that all your doctors and dentists know that you take warfarin. Before having surgery or any medical/dental procedures, tell your doctor or dentist that you are taking this medication and about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).Avoid getting injections into the muscles. If you must have an injection into a muscle (for example, a flu shot), it should be given in the arm. This way, it will be easier to check for bleeding and/or apply pressure bandages.This medication may cause stomach bleeding. Daily use of alcohol while using this medicine will increase your risk for stomach bleeding and may also affect how this medication works. Limit alcoholic beverages. Ask your doctor or pharmacist about how much alcohol you may safely drink.If you have not been eating well, if you have an illness or infection that causes fever, vomiting, or diarrhea for more than 2 days, or if you start using any antibiotic medications, contact your doctor or pharmacist right away because these conditions can affect how warfarin works.This medication can cause heavy bleeding. To lower the chance of getting cut, bruised, or injured, use great caution with sharp objects like safety razors and nail cutters. Use an electric razor when shaving and a soft toothbrush when brushing your teeth. Avoid activities such as contact sports. If you fall or injure yourself, especially if you hit your head, call your doctor right away. Your doctor may need to check you.The FDA has stated that generic warfarin products are interchangeable. However, consult your doctor or pharmacist before switching warfarin products. Be careful not to take more than one medication that contains warfarin unless specifically directed by the doctor or health care provider who is monitoring your warfarin treatment.Older adults may be at greater risk for bleeding while using this drug.This medication is not recommended for use during pregnancy because of serious (possibly fatal) harm to an unborn baby. Discuss with your doctor the use of reliable forms of birth control while taking this medication and for 1 month after stopping the medication. If you become pregnant or think you may be pregnant, tell your doctor right away. If you are planning pregnancy, discuss a plan for managing your condition with your doctor before you become pregnant. Your doctor may switch the type of medication you use during pregnancy.Since this drug can be absorbed through the skin and lungs and may harm an unborn baby, women who are pregnant or who may become pregnant should not handle this medication or breathe the dust from the tablets.Very small amounts of this medication may pass into breast milk but is unlikely to harm a nursing infant. Consult your doctor before breast-feeding.

              DRUG INTERACTIONS: See also How to Use section.Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.Warfarin interacts with many prescription, nonprescription, vitamin, and herbal products. This includes medications that are applied to the skin or inside the vagina or rectum. The following interactions listed do not contain all possible drug interactions. The interactions with warfarin usually result in an increase or decrease in the "blood-thinning" (anticoagulant) effect. Your doctor or other health care professional should closely monitor you to prevent serious bleeding or clotting problems. While you are taking warfarin, it is very important to tell your doctor or pharmacist of any changes in medications, vitamins, or herbal products that you are taking.Some products that may interact with this drug include: imatinib, marijuana (cannabis), dronabinol, mifepristone.Aspirin, aspirin-like drugs (salicylates), and nonsteroidal anti-inflammatory drugs (NSAIDs such as ibuprofen, naproxen, celecoxib) may have effects similar to warfarin. These drugs may increase the risk of bleeding problems if taken during treatment with warfarin. Carefully check all prescription/nonprescription product labels (including drugs applied to the skin such as pain-relieving creams) since the products may contain NSAIDs or salicylates. Talk to your doctor about using a different medication (such as acetaminophen) to treat pain/fever. Low-dose aspirin and related drugs (such as clopidogrel, ticlopidine) should be continued if prescribed by your doctor for specific medical reasons such as heart attack or stroke prevention. Consult your doctor or pharmacist for more details.This medication may interfere with a certain laboratory test to measure theophylline levels, possibly causing false test results. Make sure laboratory personnel and all your doctors know you use this drug.

              OVERDOSE: If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call their local poison control center at 1-800-222-1222. Canada residents can call a provincial poison control center. Symptoms of overdose may include: bloody/black/tarry stools, pink/dark urine, unusual/prolonged bleeding.

              NOTES: Do not share this medication with others.Laboratory and/or medical tests (such as INR, complete blood count) must be performed periodically to monitor your progress or check for side effects. Consult your doctor for more details.

              MISSED DOSE: For the best possible benefit, do not miss any doses. If you do miss a dose and remember on the same day, take it as soon as you remember. If you remember on the next day, skip the missed dose. Take your next dose at the regular time. Do not double the dose to catch up because this could increase your risk for bleeding. Keep a record of missed doses to give to your doctor or pharmacist. Contact your doctor or pharmacist if you miss 2 or more doses in a row.

              STORAGE: Store at room temperature away from light and moisture. Do not store in the bathroom. Keep all medications away from children and pets.Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company for more details about how to safely discard your product.

              MEDICAL ALERT: Your condition can cause complications in a medical emergency. For information about enrolling in MedicAlert, call 1-888-633-4298 (US) or 1-800-668-1507 (Canada).

              Information last revised May 2022. Copyright(c) 2022 First Databank, Inc.

              IMPORTANT: HOW TO USE THIS INFORMATION: This is a summary and does NOT have all possible information about this product. This information does not assure that this product is safe, effective, or appropriate for you. This information is not individual medical advice and does not substitute for the advice of your health care professional. Always ask your health care professional for complete information about this product and your specific health needs.

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              Formulary

              FormularyPatient Discounts

              Adding plans allows you to compare formulary status to other drugs in the same class.

              To view formulary information first create a list of plans. Your list will be saved and can be edited at any time.

              Adding plans allows you to:

              • View the formulary and any restrictions for each plan.
              • Manage and view all your plans together – even plans in different states.
              • Compare formulary status to other drugs in the same class.
              • Access your plan list on any device – mobile or desktop.

              The above information is provided for general informational and educational purposes only. Individual plans may vary and formulary information changes. Contact the applicable plan provider for the most current information.

              Tier Description
              1 This drug is available at the lowest co-pay. Most commonly, these are generic drugs.
              2 This drug is available at a middle level co-pay. Most commonly, these are "preferred" (on formulary) brand drugs.
              3 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs.
              4 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
              5 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
              6 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
              NC NOT COVERED – Drugs that are not covered by the plan.
              Code Definition
              PA Prior Authorization
              Drugs that require prior authorization. This restriction requires that specific clinical criteria be met prior to the approval of the prescription.
              QL Quantity Limits
              Drugs that have quantity limits associated with each prescription. This restriction typically limits the quantity of the drug that will be covered.
              ST Step Therapy
              Drugs that have step therapy associated with each prescription. This restriction typically requires that certain criteria be met prior to approval for the prescription.
              OR Other Restrictions
              Drugs that have restrictions other than prior authorization, quantity limits, and step therapy associated with each prescription.
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              Medscape prescription drug monographs are based on FDA-approved labeling information, unless otherwise noted, combined with additional data derived from primary medical literature.