Blood concentrations and pharmacodynamic effects of betaxolol (SL 75212) a new beta-adrenoceptor antagonist after oral and intravenous administration.

1 In normal subjects, intravenous betaxolol given in doses which inhibited the tachycardia of exercise failed to affect the peak expiratory flow rate. 2 From 2 to 48 h after administration of 150 micrograms/kg in four normal subjects, there was no significant difference between the blood levels, whether given orally or intravenously. 3 At all times, heart rate and blood pressure, at rest and during exercise, were reduced equally after administration by both routes, but the area under the curve of exercise heart rate against time was significantly smaller (P < 0.05) after intravenous drug. 4 The absolute bioavailability of betaxolol was 89 +/- 5%.