Warfarin

Key points

• Warfarin dose is guided by the INR result and clinical plan, not by symptoms or product preference.
• Many medicines, supplements, illnesses and major dietary changes can alter its anticoagulant effect.
• Do not stop, restart or change warfarin independently; both bleeding and loss of clot protection can be dangerous.

Listings are for comparison only; suitability and supply depend on the anticoagulation plan, current INR, prescription and pharmacy checks.

What warfarin is used for

Warfarin may be used for atrial fibrillation, deep vein thrombosis and other thromboembolism risks. It is not suitable for every clotting condition or every patient.

How it works

Warfarin reduces production of vitamin K-dependent clotting factors. Its effect develops and wears off gradually, and INR testing shows whether anticoagulation is within the intended range.

Important safety checks

Tell the anticoagulation team about all new or stopped medicines, antibiotics, painkillers, supplements, illness, alcohol changes and planned procedures. Keep vitamin K intake reasonably consistent rather than eliminating it. Pregnancy or pregnancy plans require prompt specialist discussion.

When to seek urgent care

Seek urgent help for vomiting or coughing blood, black stools, uncontrolled bleeding, a sudden severe headache, head injury, marked weakness or fainting, blood in urine, extensive unexplained bruising, or signs of stroke.

Further reading

• Warfarin: MedlinePlus Drug Information
• Warfarin 0.5 mg Tablets - Summary of Product Characteristics (SmPC) - (emc)
• Atrial Fibrillation