Effectiveness of Sustained-Action Isosorbide Dinitrate on Exercise-Induced Myocardial Ischemia

¹ The Donolo Institute of Physiological Hygiene, Tel Aviv University, Tel Aviv, Israel

Seventeen ambulatory men with ischemic heart disease were exercised before and after administration of one 40-mg sustained-action isosorbide dinitrate tablet. In five of them (group A) testing was done at half an hour, one, two and three hours, and in the other 12 patients (group B) two, four, six and eight hours after medication to see whether the drug provided protection from exercise-induced angina or displacement of the S-T segment of the electrocardiograms. Fourteen patients had angina during exercise before therapy. In group A favorable results were achieved with respect to disappearance of effort-induced angina pectoris and/or reduction or elimination of S-T segment displacement until three hours after medication. In group B, three of nine patients who suffered from effort-induced angina were free from angina throughout the eight-hour testing. Another was protected through six hours. Two patients were free from angina at two, four and six hours, but not at eight hours. In one patient, angina was absent only at two and four hours, and in two patients only at six hours. All patients of group B had S-T segment depression during exercise before therapy. In eight of them S-T segment displacement was reduced or absent at eight hours, in only one at two, four and six hours, in one at two and four hours, and in one at four hours only. There was no effect at all in one patient. Two patients repeated the testing procedure with isosorbide dinitrate therapy several months after the initial testing. Results were nearly identical to those of the initial tests. These patients also repeated the tests with a placebo on the day following the second testing. Two other patients repeated the tests with a placebo approximately two weeks after the initial testing. There was no evidence of effect with administration of a placebo in any of the four patients, all of whom had been protected by sustained-action isosorbide dinitrate. The results of this study suggest a beneficial effect, lasting for eight hours, of sustained-action isosorbide dinitrate on angina pectoris and effort-induced S-T segment displacement. Further studies should be carried out to confirm these preliminary results.