Comparison of antianginal activity of nicorandil, propranolol and diltiazem with reference to the antianginal mechanism.

Nicorandil was compared with placebo, propranolol and low and high doses of diltiazem therapy in 12 patients with chronic stable angina pectoris to elucidate its antianginal mechanism. A computer-assisted treadmill exercise test was performed after administration of either placebo, 30 mg of nicorandil, 40 mg of propranolol, or low-dose 60 and high-dose 120 mg of diltiazem. Exercise duration and time to the onset of ischemia were significantly increased after each drug administration and there was no significant difference in the percent increase in exercise duration between nicorandil (44 +/- 7%), propranolol (47 +/- 11%) and high-dose diltiazem (39 +/- 5%) compared with placebo. Nicorandil increased exercise duration in patients with 1-vessel disease more effectively (7.5 +/- 0.7 minutes, p less than 0.05) than either propranolol or low-dose diltiazem (6.7 +/- 0.7, 6.1 +/- 0.9 minutes, respectively). The decrease in blood pressure obtained with nicorandil was approximately the same as that with diltiazem. Nicorandil increased exercise duration associated with higher peak double product compared with low-dose diltiazem. In contrast, high-dose diltiazem increased exercise duration at the same double product as low-dose diltiazem. Propranolol increased exercise duration at a lower level of peak double product. Because our previous study demonstrated that low-dose diltiazem yielded a plasma concentration high enough to reduce coronary tone, it appears unlikely that nicorandil will reduce coronary tone further and subsequently increased coronary reserve. Therefore, left ventricular preload reduction may be the mechanism responsible for higher values of double product obtained with nicorandil.(ABSTRACT TRUNCATED AT 250 WORDS)