Indications
Farin is indicated for prophylaxis and/or treatment of thromboembolic complications associated with atrial fibrillation and/or cardiac valve replacement. It is also indicated to reduce the risk of death, recurrent myocardial infarction, and thromboembolic events such as stroke or systemic embolization after myocardial infarction, for prophylaxis and treatment of venous thrombosis and pulmonary embolism, and for transient ischaemic attacks.
⚠️ Always consult a registered physician before taking any medicine.
Pharmacology
Warfarin is a [vitamin K] antagonist which acts to inhibit the production of vitamin K by vitamin K epoxide reductase. The reduced form of vitamin K, vitamin KH2 is a cofactor used in the γ-carboxylation of coagulation factors VII, IX, X, and thrombin. Carboxylation induces a conformational change allowing the factors to bind Ca2+ and to phospholipid surfaces. Uncarboxylated factors VII, IX, X, and thrombin are biologically inactive and therefore serve to interrupt the coagulation cascade. The endogenous anticoagulation proteins C and S also require γ-carboxylation to function. This is particularly true in the case of thrombin which must be activated in order to form a thrombus. vitamin KH2 is converted to vitamin K epoxide as part of the γ-carboxylation reaction catalyzed by γ-glutamyl carboxylase. Vitamin K epoxide is then converted to vitamin K1 by vitamin K epoxide reductase then back to vitamin KH2 by vitamin K reductase. Warfarin binds to vitamin K epoxide reductase complex subunit 1 and irreversibly inhibits the enzyme thereby stopping the recycling of vitamin K by preventing the conversion of vitamin K epoxide to vitamin K1. This process creates a hypercoagulable state for a short time as proteins C and S degrade first with half lives of 8 and 24 hours, with the exception of factor VII which has a half life of 6 hours. Factors IX, X, and finally thrombin degrade later with half lives of 24, 36, and 50 hours resulting in a dominant anticoagulation effect. In order to reverse this anticoagulation vitamin K must be supplied, either exogenously or by removal of the vitamin K epoxide reductase inhibition, and time allowed for new coagulation factors to be synthesized. It takes approximately 2 days for new coagulation factors to be synthesized in the liver. Vitamin K2, functionally identical to vitamin K1, is synthesized by gut bacteria leading to interactions with antibiotics as elimination of these bacteria can reduce vitamin K2
Pregnancy & Breastfeeding
PREGNANCY & BREASTFEEDING
Warfarin must not be used during the first trimester of pregnancy, as it carries a risk of birth defects (teratogenicity). More broadly, it should be avoided in women who are pregnant or who may become pregnant, since the drug crosses the placenta and can cause fatal bleeding in the fetus.
In breastfeeding, warfarin passes into breast milk, but only in an inactive form. Studies of infants breastfed by mothers taking warfarin have shown no change in their prothrombin time. However, its effects on premature infants have not been studied.
⚠️ Talk to your doctor before taking any medicine during pregnancy or while breastfeeding.
Dosage Reference
⚠️ Reference ranges from official sources only. Consult your doctor for personalized dosing.
Side Effects & Interactions
Side Effects
No side-effect data recorded yet.