Absence of nitroglycerin-induced heparin resistance in healthy volunteers.

A previously described nitroglycerin-induced heparin resistance could not be verified by in-vitro experiments or in a randomized, double-blind, crossover trial in healthy volunteers. A clinically relevant attenuation of the anticoagulant effect of a heparin bolus (40 U.kg-1) by a concomitant infusion of nitroglycerin (100 micrograms.min-1) was absent. Activated partial thromboplastin time was not significantly different under nitroglycerin infusion as compared to placebo after heparin injection. Concentrations and activities of antithrombin III and heparin cofactor II remained unchanged during nitroglycerin infusion. An interaction of these two frequently combined drugs in patients with active thromboembolic disease or after a prolonged concomitant intravenous administration cannot be ruled out. Since this is of clinical importance, further studies must clarify a possible nitroglycerin-induced heparin resistance.