The purpose of this randomized crossover study was to determine whether nitroglycerin interacts with heparin in terms of its anticoagulative properties as determined by activated partial thromboplastin time and thrombin time. Eight healthy adults were given either a 60-minute intravenous infusion of 5 mg of nitroglycerin or a 0.9% sodium chloride solution subsequent to the administration of an intravenous injection of 5000 U of heparin. No nitroglycerin-related drug interference with heparin was observed as measured by the activated partial thromboplastin time and the thrombin time.