Unusual side effects due to warfarin.

Two cases demonstrating unusual side effects of warfarin are described. The first case illustrates the 'purple toes' syndrome, which occurred as a complication following the use of warfarin for the treatment of atrial fibrillation and stroke. The second case is an example of warfarin-induced vasculitis in a patient with a mechanical valve prosthesis. He was unable to tolerate warfarin but was successfully managed with nicoumalone, a related compound. These complications are rare but potentially dangerous effects of a commonly used agent, warfarin.