Comparative evaluation of the effects of felodipine, hydralazine, and naloxone on the survival rate in rats subjected to a "fixed volume" model of hemorrhagic shock.

Felodipine, a dihydropyridine calcium antagonist with potent arteriolar dilator properties, has been shown to enhance renal, mesenteric, coronary, and cerebral blood flows in intact animals as well as in man and to prevent deterioration of renal and mesenteric blood flows in Wiggers' model of hemorrhagic shock in dogs. In the present studies, efficacy of felodipine on 72 hr survival of rats subjected to an acute withdrawal of 40% of the blood volume was investigated. Shed blood was not reinfused in the present studies. Felodipine, whether administered before or after hemorrhage, facilitated dose-dependent increases in the survival rate up to 95%, whereas in the vehicle-treated group, the survival rate was 33%. Hydralazine, also an arteriolar dilator, in equi-hypotensive doses was not as effective as the calcium antagonist. Effects of felodipine are comparable to that of naloxone in enhancing survival. These data suggest that the salutary effects of felodipine can be related to its calcium antagonistic as well as arteriolar dilator properties.