Verapamil as A Hypotensive Agent: A Comparison, in the Anesthetized Rat, with Hydralazine, Diazoxide and Nitroprusside

Abstract

A comparison was made, in anesthetized rats, of the hypotensive actions of verapamil, hydralazine, diazoxide and nitroprusside. When these agents were administered intravenously, as single bolus injections, the hypotensive potency of verapamil was 4 times that of hydralazine, 30 times that of diazoxide, and 1/50 that of sodium nitroprusside. When, however, verapamil and nitroprusside, the two shortest-acting agents, were compared after 30 minute infusions, the potency of nitroprusside was only 4–5 times that of verapamil, since nitroprusside, and not verapamil, exhibited tachyphylaxis. The hypotensive responses to intravenous infusions of verapamil were dose-related, well maintained, and had a rapid, but somewhat less precipitous onset and offset than did those to nitroprusside. Under the present experimental conditions, verapamil proved to be a potent and effective hypotensive agent.