Generic Names:

Brand Names:

Drug Classification:

What is Warfarin?

Warfarin is an Anticoagulation Agent which slows down the coagulation process, in order prevent the formation of new blood clots, and to treat existing clots by preventing them from growing larger in size.

Warfarin slows down the coagulation process by preventing Vitamin K from producing clotting factors II, VII, IX, and X, and the anticoagulant proteins C and S, in the liver. Although Warfarin is commonly called a Blood Thinner, it does not actually affect blood viscosity.

Warfarin is mainly used to:
•   Reduce the risk of risk of heart attacks or death
•   Reduce the risk of strokes and blood clots in people who have Atrial Fibrillation, Valvular Heart Disease or Artificial Heart Valves
•   Prevent the risk of Ischaemic Strokes
•   Prevent and treat blood clots in the legs (Deep Vein Thrombosis)
•   Prevent and treat blood clots in the lungs (Pulmonary Embolism)

Side Effects

Warfarin increases your risk of severe or fatal bleeding and the more common side effects that occur are related to abnormal bleeding. Other possible side effects of Warfarin include:
•   Unusual bruising
•   Nosebleeds
•   Bleeding gums
•   Bleeding from cuts that takes a long time to stop
•   Heavier than normal menstrual or vaginal bleeding
•   Pink or brown urine
•   Red or black stools
•   Vomiting or coughing up blood
•   Death or damage of skin tissue
•   Purple Toes Syndrome
•   Abdominal or stomach pain with cramping
•   Difficulty with breathing or swallowing
•   Dizziness
•   Unexplained swelling
•   Fatigue
•   Warfarin Necrosis

You should contact your doctor, or nearest hospital, immediately if you are experiencing any of these side effects.

Warnings & Interactions

Before taking Warfarin, it is especially important that your healthcare professional is aware of all other medications you are currently taking to avoid potentially dangerous drug interactions.

Avoid excessive alcohol consumption while taking Warfarin, as this can increase the risk of bleeding and other side effects.

Increasing Vitamin K levels in the body can promote clotting and reduce the effectiveness of Warfarin. It is not necessary to avoid food products and multi-vitamins that contain Vitamin K, however you should maintain a consistent level of consumption of these products while taking Warfarin.

You should not take Warfarin if you are: prone to bleeding because of a medical condition; if you have an upcoming surgery; have very high blood pressure; or if you need a Lumbar Puncture or Epidural.

Warfarin should not be given to a victim of a stroke before it has been diagnosed by a medical professional. 80 percent of strokes are caused by a blood clots (Ischemic Stroke), but if the stroke is caused by a ruptured blood vessel in the head (Haemorrhagic Stroke), Warfarin could make the bleeding worse and increase the chance of death.

Pregnancy Warnings

Warfarin use is not recommended during pregnancy. It should only be used during pregnancy when there are no alternatives, and the benefits outweighs the risks.

Australian TGA pregnancy category: D

Breastfeeding Warnings

Warfarin use is generally considered acceptable while breastfeeding. The benefits should outweigh the risks.

Excreted into human milk: Yes

Dosage Forms

Warfarin is available in the following dosage forms:
•   Oral Tablet
•   Solution for Intravenous Injection

Additional Information

In 1933, Professor Karl-Paul Link of University of Wisconsin found that coumarin, a compound he extracted from sweet clover hays, can prevent fibrinogen in blood from forming clots by interfering with vitamin K. This unique property caused cows, which fed on sweet clover, to die from unstoppable bleeding.

In 1945, whilst recovering in a hospital from wet pleurisy, Professor Link got the idea of using a coumarin derivative as a rat poison. It was promoted and sold in 1948 as a rodenticide.

Medical researchers began to experiment with warfarin on stroke and arrhythmia patients because they knew that strokes were frequently caused by clots in the brain and the right dosage of warfarin should be able to decrease the formation of clots thus the frequency of stroke.

Warfarin was approved in 1954 for medical use in the United States, but it did not become a household name until 1955 when President Dwight D. Eisenhower had a heart attack while on vacation at his in-laws’ house in Denver. Eisenhower’s long-term treatment included Warfarin 35 mg per week. Since then, Warfarin had become the most frequently prescribed oral anticoagulant in the world.

The name “Warfarin” stems from the acronym WARF, for Wisconsin Alumni Research Foundation plus the ending -arin indicating its link with coumarin.

The effects of warfarin may be reversed with Vitamin K1, Fresh Frozen Plasma, or Prothrombin Complex Concentrate.

It is assumed that Lavrenty Beria, Nikita Khrushchev and others conspired to use warfarin to poison Soviet leader Joseph Stalin.

Warfarin is on the WHO Model List of Essential Medicines.