Anti-anginal effect of oral verapamil: evidence of dose-dependence of the effect

Abstract

The anti-anginal effect of oral verapamil was assessed in 12 patients with chronic effort-induced angina, using a single-blind, placebo-controlled protocol. The patients were given, in random order, placebo, verapamil 240 mg/day, verapamil 360 mg/day, for 24 hours, followed by a 24-hour washout period. Increase in tolerated work load, compared to a baseline bicycle exercise test, was -25 +/- 55.9 kgm/min on placebo, 137.5 +/- 96 on verapamil 240 mg/day, 212.5 +/- 129.3 on verapamil 360 mg/day (p less than 0.001). While taking verapamil in 9 patients 240 mg/day the test was interrupted with of ECG alterations; at the same work load, only 1 patient had ECG alterations while taking verapamil 360 mg/day (p less than 0.01) and 9 completed the test without ECG alterations. The pressure-rate product at maximum exercise was not significantly affected by treatments. The higher dosage of verapamil prolonged the P-R interval (p less than 0.01) but only 1 patient had first-degree AV block. It is concluded that verapamil is a powerful and safe drug in the treatment of effort-induced angina: there is evidence that the effect depends on the dosage administered.