Effects of cimetidine and ranitidine on blood coagulation

Abstract

The influence of cimetidine and ranitidine on blood coagulation and plasmatic fibrinolysis were assessed in vitro and in vivo. After an intravenous bolus of 200 mg cimetidine a marked prolongation of plasmatic thrombin time was observed, which however did not occur after 50 mg of ranitidine. In vitro addition of cimetidine (0.12 mg/ml) and ranitidine (0.06 mg/ml) again led to prolongation of plasmatic thrombin time only after cimetidine, reaching double the initial value. This requires application of cimetidine in acute intestinal haemorrhage not as a bolus, but only by drip infusion. Continuous application of 600 mg over 12 hours did not result in changes of coagulation values. In contrast, ranitidine may be administered as a bolus. Bolus injections of 50 to 100 mg did not result in any prolongation of plasmatic thrombin time. The antifibrinolytic effect of both H2-receptor antagonists was investigated in the streptokinase-induced fibrinolysis spindle of the thrombelastogram. Clear-cut antifibrinolytic properties were not demonstrable for either preparation with this method.