Warfarin

Please note: these are basic guidelines, refer to your doctor for a professional medical opinion.

Popular brand names:

Aspen-Warfarin

Drug group:

Anticoagulant drug

Prescription needed?

Yes

What does it do?

Warfarin is an anticoagulant widely used to prevent blood clots in the:

• Leg and pelvic veins (deep-vein thrombosis or DVT) - these clots can break off and travel to the lungs causing pulmonary embolism
• Heart in people with atrial fibrillation (irregular heart rhythm) or artificial heart valves - these clots can travel to the brain and cause a stroke

How should it be used?

• As warfarin’s full beneficial effects are not felt for 2-3 days, a faster-acting drug such as heparin is often used initially in people with/at high risk of developing a clot
• Avoid cranberry juice and major diet changes (especially of salads and vegetables)
• Discuss with your doctor or pharmacist before using other new medicines as warfarin has interactions with a wide range of drugs

What is the typical dosage?

Your doctor will recommend a dosage tailored to your need, but typically:

• Taken once daily, at the same time each day
• Large variation in starting and maintenance doses - adjusted according to INR levels
• Starting dose usually 10mg for 2 days
• Maintenance dose usually 3–9mg daily

How quickly will it start to work?

Within 24–48 hours; full effect after several days
                                

How long will the effects last?

2–3 days 

When should I stop using it?

Do not stop taking the drug without consulting your doctor   
                                 

Is it safe for prolonged use?

No special problems. You will need to have frequent regular blood tests to monitor your INR (International Normalised Ratio) levels.

What are the possible side effects?

The following have been reported:

• More common: bleeding
• Less common: abdominal pain, diarrhoea, rash, hair loss
• Report to your doctor before taking your next dose if you experience: excessive bruising, prolonged bleeding from a minor wound, blood in your urine/faeces, fever or jaundice

What other considerations are important?

Dosage may be adjusted by your doctor under certain conditions.

• Certain health problems: liver/kidney problems, high blood pressure, history of peptic ulcers, bleeding disorders
• Other medicines: aspirin, other non-steroidal anti-inflammatory drugs (NSAIDs), diuretics, chemotherapy, oral contraceptives, lipid-lowering drugs, amiodarone, barbiturates, cimetidine, steroids, certain laxatives, antidepressants, antibiotics ,herbal medicines
• Pregnancy and breast-feeding: Not prescribed in pregnancy, avoid during breastfeeding
• Children: Reduced dose necessary
• Over 60: No special problems
• Driving and hazardous work: Caution, risk of severe bruising and excessive bleeding
• Alcohol: Avoid major changes in alcohol consumption
• Surgery and general anaesthetics: Warfarin usually needs to be stopped before surgery