Warfarinin

Warfarinin, commonly spelled warfarin in medical literature, is an oral anticoagulant of the coumarin class used to prevent and treat thromboembolic disorders. It functions as a vitamin K antagonist by inhibiting vitamin K epoxide reductase (VKORC1), thereby reducing regeneration of reduced vitamin K and lowering production of the vitamin K–dependent coagulation factors II, VII, IX, and X, as well as proteins C and S.

Indications include prevention of stroke in nonvalvular atrial fibrillation, treatment and prevention of deep vein thrombosis and pulmonary embolism, and prevention of thrombosis in patients with mechanical heart valves or other high-risk conditions. Long-term anticoagulation is common in these settings.

Administration and monitoring: warfarin is taken by mouth and dosage is individualized. Anticoagulation is monitored with the international normalized ratio (INR); therapeutic targets vary by indication (commonly INR 2.0–3.0, or 2.5–3.5 for certain mechanical valves).

Drug interactions and diet: many medications interact with warfarin. Antibiotics, antifungals, and certain anticonvulsants can increase or decrease effect. Dietary vitamin K from leafy greens can affect anticoagulation; patients are advised to maintain consistent intake.

Reversal and safety: in cases of excessive anticoagulation or bleeding, vitamin K is administered, sometimes with prothrombin complex concentrate (PCC) or fresh frozen plasma for rapid reversal. Bridging with heparin may be used in selected patients. Adverse effects include bleeding and, rarely, skin necrosis; teratogenic risk exists in pregnancy.

History: warfarin was discovered in the 1920s after cattle were poisoned by spoiled sweet clover. It was named from the Wisconsin Alumni Research Foundation (WARF) and the -arin suffix used for related anticoagulants.