Effect of RMI 81968 a Combined Alpha- and Beta-Adrenergic Receptor Blocking Agent, on Histamine-Induced Bronchoconstriction in the Dog

Abstract

The interaction of propranolol and RMI 81968 on histamine-induced bronchoconstriction was studied in the anesthetized dog using the respiratory overflow technique of Konzett and Rössler. Propranolol, 3 and 10 μmol/kg i.v., enhanced histamine-induced bronchoconstriction. In contrast, RMI 81968, at 10 or 30 μmol/kg i.v., had no effect in this test. It is believed that the α-receptor blocking component of RMI 81968 prevents the bronchoconstriction induced by β-adrenergic receptor blockade. The results of this study suggest that RMI 81968 is less likely than propranolol to produce bronchoconstriction in asthmatic patients.