Duration of cardiac effects of timolol and propranolol

The duration of the cardiac effects of single intravenous doses of the ß‐antagonists, timolol and propranolol, was compared in 6 healthy male subjects. Timolol and propranolol were given in doses of 1 mg and 10 mg, respectively, and at specified times after their administration, ß‐blockade was assessed by the reduction of maximal exercise‐induced tachycardia and by the inhibition of the chronotropic and inotropic effects of isoproterenol. Inotropic effects were measured by changes in the pre‐ejection period of left ventricular systole obtained from systolic time intervals. There was no statistically significant difference in the timolol and propranolol time‐courses of ß‐blockade. The change in exercise‐tachycardia was maximal 5 min after ß‐antagonist infusion but dissipated rapidly so that no statistically significant change was observed 9 hr later. The chronotropic and inotropic effects of isoproterenol were almost completely antagonized for 1 V2 hr after ß‐antagonist infusion, and significant ß‐blockade could be demonstrated 9 hr later. There was no difference in the time‐course of the negative chronotropic and inotropic effects of either ß‐antagonist.

Duration of cardiac effects of timolol and propranolol Journal Articles