Key result
Single intravenous doses of timolol and propranolol showed no significant difference in the time-course of beta-blockade in healthy male subjects.
Why the study?
Does a single intravenous dose of timolol 1 mg compared to propranolol 10 mg differ in the duration of cardiac beta-blockade effects in healthy male subjects?
Does a single intravenous dose of timolol 1 mg compared to propranolol 10 mg differ in the duration of cardiac beta-blockade effects in healthy male subjects?
Single intravenous doses of timolol and propranolol exhibit similar time-courses of cardiac beta-blockade in healthy subjects.
Answers are grounded in this paper and cite their sources.
Equivalence in healthy volunteers does not inform dosing; leaves open effects in patients or with repeated administration.
The duration of the cardiac effects of single intravenous doses of the beta-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, beta-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 beta-blockade. The change in exercise-tachycardia was maximal 5 min after beta-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 11/2 hr after beta-antagonist infusion, and significant beta-blockade could be demonstrated 9 hr later. There was no difference in the time-course of the negative chronotropic and inotropic effects of either beta-antagonist.
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Achong et al. (1976) studied Healthy (n=6). Timolol vs. Propranolol 10 mg IV was evaluated on Time-course of beta-blockade (reduction of maximal exercise-induced tachycardia and inhibition of isoproterenol effects). Single intravenous doses of timolol and propranolol showed no significant difference in the time-course of beta-blockade in healthy male subjects.
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