Beta-blocking effect of single oral doses of carteolol

Carteolol is a nonselective beta-adrenergic blocking agent with intrinsic sympathomimetic activity. The duration of beta blockade after single oral doses of carteolol was studied in normal men for 72 hr by determining the heart rate response to an external stimulus, bolus intravenous isoproterenol, and an internal stimulus (graded treadmill exercise designed to achieve 85% of the subjects' maximal heart rate in 12 min). Each subject first received 5 mg of carteolol and then, at 3-wk intervals, 2.5, 15, and 60 mg carteolol and placebo in a randomized, double-blind fashion. Beta blockade was maximal 1 to 2 hr after dosing and the heart rate response to isoproterenol and exercise remained less (P less than 0.05) than placebo responses for the 72 hr after each dose of carteolol. The double product (maximal exercise heart rate x systolic blood pressure during the twelfth minute of exercise) was below (P less than 0.05) baseline values for 24 hr after all doses, for 48 hr after 15 mg, and for 72 hr after 60 mg of carteolol.