The efficacy of a once daily,
sustained release formulation of
verapamil (
Verapamil SR, 360 mg) was evaluated in 19 patients with chronic
angina pectoris using a double-blind placebo-controlled crossover protocol. Evaluation by exercise testing, 24 hour electrocardiographic ambulatory monitoring and blood
drug level assays was performed at the end of each 2 week phase, 21 to 23 hours after the last dose. After the crossover protocol, all patients were given sustained release
verapamil for 4 weeks and the evaluation was repeated. Exercise time (mean +/- SEM) increased from 7.4 +/- 0.6 minutes with placebo to 9.6 +/- 0.8 minutes with
verapamil (p less than 0.001) and to 9.5 +/- 0.7 minutes (p less than 0.001) after 4 weeks of
therapy. The mean time to 1 mm ST depression also increased significantly, from 4.5 +/- 0.4 and 4.8 +/- 0.5 minutes in bipolar leads CM5 and CC5, respectively, with placebo, to 5.5 +/- 0.6 (p less than 0.05) and 6.2 +/- 0.5 minutes (p less than 0.01) with
verapamil. Maximal ST depression and rest and peak heart rates were not altered significantly. The mean rate-pressure product was 208 +/- 9.9 with placebo and decreased to 189 +/- 7.7 (p less than 0.05) with
verapamil but rose to 200.6 +/- 10.4 (p = NS) after 4 weeks of
therapy. The mean hourly heart rates were lower with the
drug than with placebo throughout the 24 hour period but there was no significant
bradycardia,
arrhythmia or
heart block.(ABSTRACT TRUNCATED AT 250 WORDS)