Limited efficacy of three times daily isordil dinitrate

Mean duration of exercise time to angina at different hours during days on which eight men with stable angina were given isosorbide dinitrate (ISDN) or placebo at 8 AM, 1 PM, and 6 PM (arrows). A signficant increase in exercise duration occurred after each dose of ISDN; however, the total duration of benefit was only about six hours.