Orfarin Adverse Reactions

Commonly reported (1-10%) undesirable effects of warfarin treatment are the bleeding complications. The over-all rate for bleeding is about 8% per year for total bleeding, consisting of minor bleeding (6% per year), severe bleedings (1% per year) and fatal (0.255 per year). The most common risk factor for intracranial bleeding is untreated or uncontrolled hypertension. Likelihood of bleeding increases as the INR elevates significantly above the target range. If bleeding occurs when the INR is within the target range, there usually exist another comorbid condition which should be investigated. Other common undesirable effects are nausea, vomiting and diarrhoea.
Coumarin necrosis is a rare complication of warfarin therapy. It manifests initially as swelling and darkening skin lesions usually in the lower extremities or buttocks, but may appear elsewhere as well. Later the lesions become necrotic. 90% of the patients are women. Lesions appear on the 3rd to 10th day after starting warfarin therapy and relative deficiency of antithrombotic proteins C and S is considered as an etiologic factor. Hereditary deficiency of protein C or S may predispose the patient to the complication. For this reason, warfarin therapy must be initiated in these patients concomitantly with heparin and using small doses of warfarin. If these adverse reactions occurs, warfarin therapy must be discontinued and heparin therapy continued until the lesions have healed or become scarred.
Purple toe-syndrome is an even more rare complication of warfarin therapy. Patients, usually male, typically have arteriosclerosis. Warfarin is thought to cause hemorrhages to the atheromatous plaques leading to microembolization. This cause symmetrical purple skin lesions in the toes and soles which is associated with burning pain. Warfarin therapy must be discontinued and thereafter the skin lesions disappear slowly.
Other rare adverse events reported during warfarin treatment are vasculitis, tracheal calcification, reversible hepatic enzyme elevation, cholestatic hepatits, reversible alopecia, rash, priapism and allergic reactions (manifested usually as skin rash).