BLOCKADE OF THE BETA ADRENERGIC RECEPTORS

¹ Department of Pharmacology, Medical College of Georgia, Augusta, Georgia

The ability of a drug to convert ethylnorepinephrine (ENE) from a depressor to a pressor agent and to reduce but not reverse the depressor response to isoproterenol has been shown to indicate blockade of the beta adrenergic receptors. ENE "reversal" alone is indicative of beta receptor blockade only if the drug in question is not a vasoconstrictor agent.

Using these two effects as criteria, isoprophenamine has been shown to exert a beta receptor blocking action that differs from DCI only in its duration of action, DCI acting approximately 5 times longer than isoprophenamine. ENE itself, in large doses (500 µg/kg or more), and DCE, the dichloro analog of epinephrine, also exert weak beta receptor blocking actions.