STERIC ASPECTS OF ADRENERGIC DRUGS. V. BETA ADRENERGIC BLOCKING EFFECTS OF OPTICAL ISOMERS OF METHOXAMINE AND ISOPROPYLMETHOXAMINE

¹ College of Pharmacy, The Ohio State University, Columbus, Ohio

Beta adrenergic receptor blocking actions of (-) and (+) isomers of methoxamine and related compounds were investigated in isolated guinea-pig tracheal chain preparations. (-)-Isoproterenol was used as the agonist and tissue was exposed to antagonist for 3 min. All agents except (+)-isopropylmethoxamine produced a concentration-dependent parallel shift of dose-response curves of the agonist to the right. pA₂ values for (-)-isopropylmethoxamine, (-)-methoxamine and (+)-methoxamine were 6.53, 6.25 and 4.37, respectively. (±)-Desoxymethoxamine also was found to produce a significant blockade of beta adrenergic receptors. The pA₂ value for (±)-desoxyisopropylmethoxamine was 4.85 and that for (±)-desoxymethoxamine was 5.09. (±)-Desoxymethoxamine was found to have approximately the same activity as (+)-methoxamine, whereas (±)-desoxyisopropylmethoxamine was much more active than (+)-isopropylmethoxamine.