PHARMACOLOGY OF A GROUP OF PHENYLPIPERAZINE TETRAZOLE DERIVATIVES WITH ADRENERGIC BLOCKING ACTIONS

¹ Instituto Miles de Terapéutica Experimental, México, D. F., México

A group of phenylpiperazine tetrazole derivatives of which 4-phenyl-1-[2-(5-tetrazolyl)ethyl] piperazine trihydrochloride (MA1277, phenpiperazole) is a typical member, have been found to be potent alpha antiadrenergic compounds possessing characteristics which make them somewhat different from other substances with this activity. Thus, as compared to most antiadrenergic compounds, MA1277 showed greater potency in vivo than in vitro and evoked proportionately greater blockade of sympathetic nerve stimulation. Moreover, its action was much longer than that of drugs such as azapetine and phentolamine and, unlike that of phenoxybenzamine, was immediate in onset and apparently of the competitive equilibrium type. Furthermore, in contrast to dihydroergotamine and tolazoline, it produced no smooth muscle stimulation. The chronic administration of the drug was followed by sustained lowering of blood pressure in mecamylamine hypertensive dogs.