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

Abstract

When verapamil, hydralazine, diazoxide and nitroprusside were administered to rat i.v. 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 verapamil and nitroprusside, the 2 shortest-acting agents, were compared after 30 min infusions, the potency of nitroprusside was only 4-5 times that of verapamil since nitroprusside, and not verapamil, exhibited tachyphylaxis. The hypotensive responses to i.v. infusions of verapamil were dose-related, well maintained and had a rapid, but somewhat less precipitous onset and offset than did those to nitroprusside. Verapamil was a potent and effective hypotensive agent.