Effectiveness of isosorbide dinitrate and nitroglycerin in relieving angina pectoris during uninterrupted exercise

Twenty patients with ischemic heart disease documented by coronary angiograms or ST segment depression in the ECG during treadmill walking, were administered sublingual nitroglycerin 0.3 to 0.6 mg on one occasion and a chewable form of isosorbide dinitrate 5 mg on another occasion during treadmill walking when anginal discomfort was definitely present at a mild degree of intensity. Despite continued walking at a constant speed and grade, angina was relieved in all patients, completely in most patients, partially in a few. The average time from administration of the medication to onset to relief was 74.7 seconds for nitroglycerin and 107.6 seconds for chewable isosorbide dinitrate. Average time to complete relief or maximal incomplete relief was 190.3 seconds for nitroglycerin and 315.1 seconds for chewable isosorbide dinitrate. Ischemic electrocardiographic changes were reverted toward normal by nitroglycerin in 13 subjects and by isosorbide dinitrate in 15. The differences in onset to complete relief were all statistically significant indicating that nitroglycerin is more rapid in its action than is chewable isosorbide dinitrate.