A clinical and in vitro study on the possible interaction of intravenous nitrates with heparin anticoagulation

Abstract

It has been reported that intravenous nitrates inhibit the anticoagulant effect of heparin. This possible interactior has potentially serious implications for the management of patients with acute coronary ischemic syndromes. This possible interaction was assessed prospectively in a clinical and in an in vitro study involving 24 patients receiving both drugs for the management of unstable angina pectoris. There was a small in hibitory effect of intravenous glyceryl trinitrate or isosorbide dinitrate on the anticoagulant effect of heparin in 3 of 24 case in vivo, as assessed by activated partial thromboplastin time measurements. Nitrates or propylene glycol had no effect or heparin activity in vitro. It was concluded that there may be an inhibitory effect of nitrates on anticoagulation in a small miority of patients, but close attention to detail in monitoring heparin anticoagulation is far more important. Copyright © 1994 Wiley Periodicals, Inc.