A comparison of sustained release verapamil versus atenolol for 24 h protection from exercise-induced angina pectoris

We have compared the efficacy of a once daily 360 mg sustained release preparation of verapamil (SRV) with that of once daily 100 mg atenolol in exercise-induced angina. The study was randomized, double-blind and cross-over in design involving 30 patients with chronic stable angina. A 2-week run-in placebo phase was followed by two 4-week periods of active treatment. Patients underwent exercise stress tests at 6 and 24 h post-dose at the end of each treatment phase. After the placebo phase, patients had significantly increased times to both 1 mm ST depression and angina at 6 h (afternoon stress test) compared to 24 h post-dose (morning test). The two treatments were found to be equivalent in terms of several indices of anti-anginal efficacy. The only significant differences between treatments were in relation to indices of heart rate, which were consistently lower with atenolol than with SRV. We conclude that once daily sustained release verapamil 360 mg has equivalent anti-anginal efficacy to once daily atenolol 100 mg. A lower angina threshold seems to occur in the morning in patients with ischaemic heart disease suggesting a diurnal variation.