Activity and duration of action of pindolol and alprenolol compared in healthy volunteers.

An improvement in the prognosis of myocardial infarction has been reported after long term treatment with alprenolol 200 mg twice daily. Therefore, an experiment was carried out to find the dose of pindolol given once daily which would show cardiac beta-adrenoceptor blockade at least equipotent to that obtained during treatment with alprenolol 200 mg twice daily. Cardiac beta-adrenoceptor blocking activity and its time course during treatment with pindolol (15 mg and 20 mg given once daily) and alprenolol (200 mg given 12-hourly) for three days were compared in 6 healthy volunteers. The reduction in exercise-induced tachycardia as a measure of cariac beta-adrenoceptor blockade was significantly greater after pindolol 15 mg and 20 mg than after alprenolol 200 mg. On the morning of the fourth day, i.e. 24 h after the last dose of pindolol and only 12 h after the last dose of alprenolol, the effects of pindolol at both dose levels were slightly greater than those of alprenolol. This difference was not statistically significant. It can be concluded that pindolol 15 mg once daily produces a cardiac beta-adrenoceptor blockade at least equipotent to that of alprenolol 200 mg given 12-hourly.