Efficacy, duration and mechanism of action of nifedipine in stable exercise-induced angina pectoris.

The duration of effect of single oral doses of 10 and 20 mg of nifedipine was studied in 10 patients with angiographically proven coronary artery disease and with stable exercise-induced angina pectoris. In a randomized double-blind manner exercise tests were carried out 1 hour before and 1, 2, 4 and 6 h after the administration of placebo, nifedipine 10 mg(N10) and nifedipine 20 mg(N20). Compared with the placebo both N10 and N20 produced a statistically significant increase in exercise tolerance at 1(P less than 0.05), 2(P less than 0.01), 4(P less than 0.01) and 6(P less than 0.05) hours after N10 and at 1(P less than 0.01), 2(P less than 0.01), 4(P less than 0.01) and 6(P less than 0.05) hours after N20. At peak exercise the product of heart rate X systolic blood pressure (RPP) was significantly increased compared with placebo at 2, 4 and 6 h after N10 and at 2, 4 and 6 h after N20 with maximal ST-segment depression unchanged. At the same duration of exercise at which angina had occurred during control studies the RPP was unaffected by nifedipine while a statistically significant reduction of ST-segment depression was seen at 1, 2 and 4 h after N10 and at 1, 2 and 4 h after N20. Direct measurements of great cardiac vein flow during exercise in two patients showed that nifedipine is effective in preventing the abnormal increase of exercise-induced coronary tone in the area supplied by stenotic vessels.(ABSTRACT TRUNCATED AT 250 WORDS)