Comparison of the autonomic effects of procainamide and N- acetylprocainamide in the dog

RD Reynolds and RJ Gorczynski

The autonomic effects of procainamide (PA) and N-acetylprocainamide (NAPA) were studied in anesthetized dogs. High plasma concentrations of PA (31 +/- 1.3--64 +/- 3.4 micrograms/ml) and NAPA (64 +/- 3.4--127 +/- 8.3 micrograms/ml)) reduced base-line mean arterial pressure and heart rate and attenuated the pressor and positive chronotropic responses to bilateral carotid occlusion and the negative chronotropic response to vagal stimulation. Neither drug reduced the pressor or positive chronotropic responses to catecholamines (epinephrine, phenylphrine, isoproterenol), however. In fact, at some doses PA and NAPA accentuated the pressor and positive chronotropic effects of epinephrine. Similarly, the depressor response to acetylcholine was not reduced by these drugs; it was significantly increased at some doses. In the isolated hindlimb (constant flow) PA and NAPA reduced the pressor response to preganglionic (sympathetic chain) stimulation but not to postganglionic (femoral and sciatic nerves) stimulation. We conclude that NAPA, like PA, at high plasma levels is vagolytic and attenuates baroreceptor-mediated reflexes associated with reduced arterial pressure. These effects appear to be due to ganglionic blockade.

Volume 212, Issue 3, pp. 579-583, 03/01/1980
Copyright © 1980 by American Society for Pharmacology and Experimental Therapeutics