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.