Evaluation of the efficacy and duration of action of isosorbide mononitrate in angina pectoris

The magnitude and duration of the antianginal and anti-ischemic effects of isosorbide mononitrate (IS-5-MN), 20 mg, were determined in 10 patients with chronic stable angina pectoris. An exercise test (treadmill, Bruce protocol) was performed before and at 1, 6, 8 and 10 hours after oral administration of the drug. The patients were randomly assigned to receive IS-5-MN or placebo, and after 1 week of therapy were crossed over to the other formulations. The drug increased the exercise duration from 321 to 455 seconds at 1 hour (p less than 0.001). Time to moderate angina increased from 237 to 324 seconds (p less than 0.05) and time to ST depression greater than or equal to 1 mm increased from 150 to 307 seconds (p less than 0.01) at 1 hour. Placebo had no effect on any of the exercise parameters. Although partially attenuated at 6 hours, the effect of IS-5-MN remained statistically significant even at 8 hours, but not at 10 hours. It is concluded that the duration of action of a single tablet of IS-5-MN, given orally, is 8 hours.