Efficacy of once daily penbutolol in chronic stable angina. An objective comparison with long-acting propranolol

The effects of penbutolol (40 mg daily) and long-acting propranolol (160 mg daily) were assessed in 26 patients with chronic stable angina in a placebo-controlled randomised double-blind crossover study with 2-weekly treatment periods. In addition to conventional subjective assessment, serial multistage treadmill exercise was used to obtain objective data on drug efficacy and 24-hr ambulatory electrocardiography performed for diurnal heart rate analysis. The mean exercise time of 6.3 +/- 0.5 (SEM) min on placebo increased to 7.3 +/- 0.6 min on penbutolol (P less than 0.01) and to 7.9 +/- 0.5 min on propranolol (P less than 0.001). The pre-exercise resting heart rate was 73 +/- 2 beats/min on placebo and decreased to 63 +/- 2 beats/min on penbutolol (P less than 0.001) and 58 +/- 2 beats/min on propranolol (P less than 0.001). The maximum exercise heart rate was similarly reduced by both drugs and there was a corresponding reduction in peak exercise double product. The time-corrected maximum ST segment depression was reduced by both drugs and neither produced a delay in ST segment recovery. Both drugs effected significant reductions in ambulatory maximum hourly heart rates throughout 24 hr. The lowest observed heart rate on penbutolol was 40 beats/min and 34 beats/min on propranolol. Penbutolol is an effective antianginal agent with a profile of action similar to that of propranolol.