Effects of Practolol, a New Adrenergic Receptor Blocking Agent on Cardiovascular Responses

Abstract

The claim that practolol, 4-(2-hydroxy-3-isopropyl-aminopropoxy)acetanilid, is a cardioselective β-adrenergic receptor blocking agent was investigated by testing this compound in cats and in hyperthyroid rabbits for its ability to block certain cardiovascular responses. Doses of 1, 2, 5, and 10 mg./kg. administered intravenously were ineffective in abolishing completely the pressor response to bilateral carotid occlusion. After the administration of either 2, 5, or 10 mg./kg. of this agent, the pressor response due to injected norepinephrine (3 mcg./kg.) was unaffected. However, these doses produced a moderate to marked depression of the increase in chronotropic response caused by the injection of norepinephrine (3 mcg./kg.) and isoproterenol (0.3 mcg./kg.) and the tachycardia attendant with hyperthyroid states. The blockade of the resting tachycardia in hyperthyroid rabbits was significant at all dose levels of practolol (p ⪕0.01 or 0.02). Only the 10-mg./kg. dose was found to produce a transient hypotension in cats.