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Warfarin

Plasorin, Varfarin, Warfmadin, Warsu · ATC code B01AA03

Also known as: Varfarin, Warfarine, Warfarina

Key facts
Active substance
Warfarin
Drug class
Vitamin K antagonist
ATC code
B01AA03
Authorisation
authorised nationally; no central EU authorisation
Information as of
2026-11-03

Boxed warning

  • Warfarin sodium can cause major or fatal bleeding [see Warnings and Precautions (5.1)].
  • Perform regular monitoring of INR in all treated patients [see Dosage and Administration (2.1)].
  • Drugs, dietary changes, and other factors affect INR levels achieved with warfarin sodium therapy [see Drug Interactions (7)].
  • Instruct patients about prevention measures to minimize risk of bleeding and to report signs and symptoms of bleeding [see Patient Counseling Information (17)].

Key facts

Warfarin is an oral vitamin K antagonist anticoagulant. Per the US label it is used to prevent and treat venous thromboembolism and thromboembolic complications of atrial fibrillation, heart valve replacement and myocardial infarction; dosing is guided by the INR.

What it is used for

  • Prophylaxis and treatment of venous thrombosis and pulmonary embolism
  • Prophylaxis and treatment of thromboembolic complications of atrial fibrillation and/or cardiac valve replacement
  • Reduction of the risk of death, recurrent myocardial infarction and thromboembolic events (e.g. stroke) after myocardial infarction

Dosing

  • Dose is individualised to the INR; most indications target INR 2.5 (range 2 to 3); mechanical mitral valves and caged ball/caged disk valves target INR 3 (range 2.5 to 3.5)
  • Genotype unknown: usual initial dose 2 to 5 mg once daily; typical maintenance dose 2 to 10 mg once daily
  • CYP2C9 and VKORC1 genotypes, age and Asian ancestry can lower dose needs; loading doses are not recommended
  • INR daily after the initial dose until stable, then generally every 1 to 4 weeks
  • Overlap with full-dose heparin for 4 to 5 days and until the INR is therapeutic
  • Missed dose: take as soon as possible the same day; do not double the next day
  • No dosage adjustment in renal impairment, but monitor INR more often

Contraindications

  • Pregnancy, except in women with mechanical heart valves at high risk of thromboembolism
  • Haemorrhagic tendencies, blood dyscrasias, active bleeding or ulceration, CNS haemorrhage, cerebral aneurysm, dissecting aorta, bacterial endocarditis
  • Recent or planned CNS or eye surgery; spinal puncture, major regional or lumbar block anaesthesia
  • Threatened abortion, eclampsia, preeclampsia; malignant hypertension
  • Unsupervised patients with likely non-compliance; hypersensitivity to warfarin

Important warnings

  • Boxed warning: can cause major or fatal bleeding; monitor INR regularly; drugs, diet and other factors alter the INR
  • Bleeding risk factors include INR > 4, age 65 or older, variable INRs, prior GI bleeding, hypertension, renal impairment and long therapy
  • Skin and tissue necrosis (<0.1%), calciphylaxis, acute kidney injury, atheroemboli/cholesterol microemboli (“purple toes”)
  • Do not use as initial therapy in HIT/HITTS (limb ischaemia, gangrene)
  • Protein C or S deficiency: heparin overlap for 5 to 7 days at initiation may reduce necrosis

Side effects

  • Main risk: haemorrhage, including fatal bleeding
  • Hypersensitivity reactions, vasculitis, hepatitis and raised liver enzymes
  • Nausea, vomiting, diarrhoea, taste disturbance, abdominal pain, bloating
  • Rash, dermatitis, pruritus, alopecia; tracheal calcification; chills

Interactions

  • CYP2C9, 1A2 and 3A4 inhibitors (e.g. amiodarone, fluconazole, metronidazole, cotrimoxazole) raise the INR; inducers (e.g. rifampin, carbamazepine) lower it
  • Anticoagulants, antiplatelets, NSAIDs and serotonin reuptake inhibitors increase bleeding risk
  • Antibiotics and antifungals: monitor INR closely when starting or stopping
  • Botanicals (e.g. St. John’s wort, ginkgo, garlic) and dietary vitamin K: keep vitamin K intake consistent

Pregnancy and breastfeeding

  • Contraindicated except with mechanical heart valves at high thromboembolic risk; first-trimester exposure caused malformations (warfarin embryopathy) in about 5% of exposed offspring
  • Effective contraception during treatment and for at least 1 month after the last dose
  • Not detected in human milk in a small study; monitor breastfed infants for bruising or bleeding

Summary of the official product information, written with AI on 2026-11-03. Every number was checked automatically against the original text. Not reviewed by a physician – the full official text is authoritative.

Full official text →

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For patients

Patient information (US)

This product has no separate US patient information.

Authorisation and brand names by country

Medicines with exactly this active-substance composition, as listed in the national registers – alphabetical and without ranking. Whether a product is currently available is not shown here.

Germany

  • Coumadin®Teofarma S.R.L. · 1 register entry

Source: EMA – Article 57 product data (EU/EEA), as of 2026-11-03

Turkey

  • PlasorinPLATİN KİMYA MÜMESSİLLİK VE DIŞ TİC. A.Ş. · 2 register entries
  • VarfarinMÜNİR ŞAHİN İLAÇ SAN. VE TİC A.Ş. · 2 register entries
  • WarfmadinSANOFİ SAĞLIK ÜRÜNLERİ LTD. ŞTİ. · 2 register entries
  • WarsuKAYA BEŞERİ İLAÇ SAN. VE TİC. A.Ş. · 1 register entry

Source: TİTCK – Ruhsatlı Beşeri Tıbbi Ürünler Listesi, as of 2026-11-03

Brand names in 23 more European countries
Belgium
Marevan
Croatia
Martefarin
Cyprus
Aldocumar, Warfant
Czechia
Warfarin Orion
Denmark
Marevan, Warfarin Orion
Estonia
Marevan
Finland
Marevan, Warfarin Orion
France
Coumadine
Hungary
Marfarin, Warfarin Orion
Iceland
Warfarin Teva
Ireland
Warfant, Warfarin Teva
Italy
Coumadin
Latvia
Orfarin, Warfarin Grindeks
Lithuania
Orfarin, Warfarin Grindeks
Luxembourg
Marevan
Malta
Warfarin
Norway
Marevan, Warfarin Orion
Poland
Warfin
Portugal
Enifrav, Varfine
Slovakia
Warfarin Orion
Slovenia
Marevan
Spain
Aldocumar
Sweden
Waran, Warfarin Orion

EMA – Article 57 product data (EU/EEA), 2026-11-03

Medelix receives no money from pharmaceutical companies. Brand names are listed alphabetically and without ranking.

Another question about this substance?

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Sources

  1. U.S. Food and Drug Administration. Warfarin Sodium (Teva Pharmaceuticals USA, Inc.) – Prescribing Information, 2025-06-17. DailyMed (NLM), 2026-11-03. https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=0cbce382-9c88-4f58-ae0f-532a841e8f95
  2. EMA – Article 57 product data (EU/EEA), 2026-11-03. https://www.ema.europa.eu/en/human-regulatory-overview/post-authorisation/data-medicines-iso-idmp-standards-post-authorisation/public-data-article-57-database
  3. TİTCK – Ruhsatlı Beşeri Tıbbi Ürünler Listesi, 2026-11-03. https://www.titck.gov.tr/dinamikmodul/85
  4. Wikidata (CC0): ATC B01AA.

Editorial: Medelix editorial team · last updated 2026-11-03 · How these pages are made · Report an error

Source: U.S. Food and Drug Administration (FDA), prescribing information, via DailyMed (NLM); public domain. Not advertising, not a treatment recommendation. For questions about your own treatment, ask your doctor or pharmacist.