Beta‐2 adrenoceptor blocking activity of penbutolol and propranolol at very low doses

Abstract
The relative potency of penbutolol, a new β adrenergic receptor blocking agent, was compared with propranolol by a four-point assay on healthy male subjects. A dose-response relationship to intravenous doses of propranolol in the microgram range was obtained during a steady state of infusion of epinephrine. Two subjects underwent the entire assay according to the Latin square design and four others each underwent one schedule of design on different days. The potency of penbutolol thus assessed was consistent with reported results. This study emphasizes the importance of intersubject variation and differential receptor sensitivity in individuals. The use of epinephrine as a β receptor adrenergic agonist for evaluation of selective β adrenergic receptor blocking activities is discussed.

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