Cardiovascular Actions of a New Dihydropyridine Calcium Antagonist, 8363-S

The systemic and coronary hemodynamic actions of a new dihydropyridine, 8363-S, were compared with nifedipine and nicardipine in conscious, instrumented dogs following intravenous and oral administration. All agents produced similar reductions in arterial and ventricular pressures and increases in heart rate, dP/dt, and coronary blood flow velocity, following intravenous infusion. Following oral administration, all agents had qualitatively similar actions; however, there was a marked difference in potency. 8363-S was found to be most potent in that 0.25 mg/kg produced equivalent or larger changes from control than 0.5 mg/kg nifedipine or 1.0 mg/kg nicardipine. Furthermore, 8363-S had a longer duration of action following oral administration. The results suggest that important differences in bioavailability exist amongst dihydropyridines which may have important therapeutic implications.