COMPARATIVE BETA-BLOCKING POTENCIES OF ACEBUTOLOL AND PROPRANOLOL RELATIVE TO PLASMA DRUG LEVELS

  • 1 January 1981
    • journal article
    • research article
    • Vol. 19  (11) , 473-478
Abstract
In a double-blind placebo cross-over study, the .beta.-blocking potencies of acebutolol and propranolol were compared in 10 healthy subjects under steady-state conditions of oral drug administration. .beta.-adrenergic blockade, determined by the degree of attenuation of tachycardia induced by standardized multistage treadmill exercise, was correlated with dose as well as with the plasma levels of the 2 .beta.-antagonists. On a weight-for-weight basis, propranolol was about 4 times as potent as acebutolol in inhibiting exercise-induced tachycardia and in reducing the heart rate times systolic blood pressure product due to exercise. A weak correlation was demonstrated between the degree of .beta.-blockade and plasma concentrations of propranolol (r = 0.381, P < 0.01) or acebutolol (r = 0.333, P < 0.001), there being up to 20- to 24-fold interindividual variation in plasma level for a given dose of each compound. Plasma acebutolol levels were associated with at least 2-fold greater levels of its acetyl homolog metabolite. A positive linear correlation was found between percentage .beta.-blockade and the corresponding doses of propranolol (r = 0.503, P < 0.001) and of acebutolol (r = 0.574, P < 0.001). The overall data provide little support for the use of plasma levels of acebutolol and propranolol as a guide to .beta.-blocking therapy with these compounds.