Possible interactions of indomethacin and nitrates in angina pectoris

Intravenous indomethacin has been reported to diminish coronary flow in patients with angina. There is also evidence that indomethacin attenuates or abolishes the coronary dilator and venodilator effects of nitroglycerin. In 11 patients with stable angina of effort, prior administration of 100 mg of indomethacin appeared to increase (0.10 greater than p greater than 0.05), rather than reduce, the work load achieved compared with placebo on a double-blind basis. The increase in work load when patients were given nitroglycerin was not significantly changed after they were given indomethacin. Therefore, this study does not support the suggestion either that prostaglandins play a significant role in coronary vasoregulation on effort or that prostacyclin is an important mediator of the therapeutic action of nitroglycerin. From a practical therapeutic viewpoint, there is apparently no danger of aggravating stable, exercise-induced angina or of abolishing the benefit normally expected from nitroglycerin when patients with angina are given indomethacin in doses comparable to those used in this study.