Propranolol in angina pectoris: Comparison of therapy given two and four times daily

Abstract

The efficacy of propranolol used twice daily versus that of propranol used four times daily was compared in 25 patients with stable angina pectoris. All had been treated with propranolol for angina for an average of 14 months (range 2 to 36) and all had experienced symptomatic or objective improvement, or both, in exercise tolerance during this period. The total daily dose of propranolol (160 mg in 21 patients and 320 mg in 4 patients) was maintained throughout the trial period. The study was double blind and crossover in design and each dose schedule was prescribed for a 2 month period. No adverse effects occurred when patients altered treatment schedules. The average number of anginal attacks experienced was 6 ± 6 and 7 ±8 per month (mean ± 1 standard deviation [SD]) for months 1 and 2 with therapy twice daily and 6 ± 5 and 6 ± 6 per month for months 1 and 2 with therapy four times daily (difference not significant). The times from beginning of exercise to angina 6 and 8 hours after a previous dose of propranolol during therapy twice daily were, respectively, 356 ± 138 and 358 ± 147 seconds for month 1 and 375 ± 137 and 385 ± 148 seconds for month 2. These values were similar to those obtained 2 and 4 hours after the previous dose during therapy four times daily (350 ± 143 and 351 ± 157 seconds for month 1 and 375 ± 142 and 366 ± 137 seconds, respectively, for month 2). The values for S-T segment depression, heart rate, systolic blood pressure and rate-pressure product at the onset of angina were similar during therapy twice daily and during therapy four times daily. Plasma propranolol concentrations were similar during months 1 and 2 of therapy with the same schedule. After a previous dose, the values during month 2 were 116.3 ± 93.8 at 6 hours and 93.6 ± 88.8 ng/ml at 8 hours with therapy twice daily and 104.5 ± 74.3 at 2 hours and 93.9 ± 70.4 ng/ml at 4 hours during therapy four times daily. The study shows that in the treatment of stable angina pectoris, propranolol given twice daily is as effective as that given four times daily.