The effect of beta-adrenoceptor antagonists on the alpha-adrenoceptor blockade produced by phenoxybenzamine.
The effect of beta-adrenoceptor antagonists on the irreversible alpha-adrenoceptor blockade produced by phenoxybenzamine was studied in dogs. The pressor effects of adrenaline were revived after the inhibition by the alpha-receptor block by (+/-) propranolol, (-) INPEA, (+/-) MJ 1999 and (+/-) butoxamine. The enantiomers (+) propranolol and (+) INPEA were ineffective in this regard. (+/-) Practolol also did not revive the pressor effect of the amines. The alpha-receptor mediated effect of the amines, in the nictitating membrana-receptor blockade. It is concluded that (1) blockade of the peripheral (beta-2) receptors is essential for the revival of the pressor effects, (2) local anesthetic effect of the beta-antagonists is not involved. Further work using a series of doses of agonists and antagonists of alpha-and beta-receptors is indicated to clarify the nature of this drug-interaction.
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002395:Catecholamines / Q000494:pharmacology; D004285:Dogs; D004347:Drug Interactions; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects; D009541:Nictitating Membrane / Q000187:drug effects; D010643:Phenoxybenzamine / Q000494:pharmacology*; D011941:Receptors, Adrenergic / Q000187:drug effects*; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects*; D013154:Spleen / Q000187:drug effects; D013997:Time Factors
D000319:Adrenergic beta-Antagonists; D002395:Catecholamines; D011941:Receptors, Adrenergic; D011942:Receptors, Adrenergic, alpha; D010643:Phenoxybenzamine