Warfarin — Drug Interactions, Alcohol & Pregnancy Guide

Last reviewed: · Source: US FDA drug label database

About Warfarin

Warfarin is an anticoagulant (blood thinner) that prevents blood clots. It requires regular INR blood tests as many foods, drugs, and illness can affect its level. It is being increasingly replaced by NOACs (e.g. apixaban, rivaroxaban) but remains widely prescribed.

Also sold as: Coumadin, Marevan

Drug class Anticoagulant (vitamin K antagonist)
Used for DVT prevention and treatment, Pulmonary embolism, Atrial fibrillation (stroke prevention), Mechanical heart valves
Max adult dose Individualised based on INR target; typically 2-10mg daily
OTC in UK Prescription only

Warfarin and Alcohol

🟡 USE WITH CAUTION

Use caution — even moderate alcohol can unpredictably alter how warfarin works, making your blood either too thin or not thin enough.

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Warfarin in Pregnancy

🔴 AVOID

Warfarin is contraindicated in pregnancy — it causes fetal warfarin syndrome and bleeding. Heparin is the safe anticoagulant in pregnancy.

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Warfarin — Drug Combinations

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Warfarin + Aspirin
Avoid — aspirin significantly increases bleeding risk when taken with warfarin a…
🔴
Warfarin + Ibuprofen
Avoid — ibuprofen increases bleeding risk and can significantly raise warfarin l…
🟡
Warfarin + Paracetamol
Paracetamol is the safest painkiller on warfarin, but regular use (more than a f…

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Not sure if Warfarin is safe with your other medications?

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