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Ten hospitalized patients performed two exercise tests per day on five consecutive days to determine the efficacy and duration of action of three sublingual long-acting nitrate preparations: isosorbide dinitrate, pentaerythritol trinitrate, and erythrityl tetranitrate. The duration of exercise to the point of ischemia, manifest as typical anginal pain and/or 1.0 mm ST-segment depression, was determined 45 min and 100 min after each long-acting nitrate was administered. These results were compared with the duration of exercise after placebo and two minutes after nitroglycerin administration. The mean durations of exercise in two tests after placebo were 62.5 sec and 58.4 sec (not significant) and the mean durations of exercise after nitroglycerin administration were 90.5 sec and 88.4 sec, both different from placebo ( P < .001). There was no difference from placebo found 55 min after taking nitroglycerin. The mean durations of exercise 45 min after erythrityl tetranitrate, isosorbide dinitrate and pentaerythritol trinitrate were 89.1, 87.5, and 87.5 sec respectively and all were different from placebo ( P < .01). Mean durations of exercise 100 min after erythrityl tetranitrate, isosorbide dinitrate, and pentaerythritol trinitrate were 76.4, 75.5, and 69.7 sec and none were significantly different from placebo. This study indicates that each long-acting nitrate is effective for at least 45 min and suggests that they should not be given on a fixed dosage schedule but rather should be taken prophylactically whenever an angina-provoking situation is anticipated.

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