Drugs affecting blood coagulation and fibrinolysis

Abstract

This chapter discusses several drugs that affect blood coagulation and fibrinolysis. The most common adverse effect of the coumarin congeners is bleeding. Coumarin congeners are now well established in the primary prevention of thromboembolic events in patients with atrial fibrillation. Warfarin-induced skin necrosis is a rare but potentially devastating effect. It occurs during the first days of administration and is caused by a transient hypercoagulable state, because of the rapid fall in concentrations of protein C, a vitamin K-dependent anticoagulant factor. Heparin-induced thrombocytopenia with thrombosis remains a major concern. This adverse effect is of immune origin and results from an interaction of antibodies with heparin-platelet factor 4 complexes on the platelet surface. The immune character explains the delayed onset of this adverse effect, after six or more days of heparin administration, unless the patient has previously been sensitized to heparin, in which case it can occur earlier. The immune reaction induces platelet activation and aggregation; the platelet-rich nature is reflected by the whitish appearance of the thrombus in vivo.