Effect of a new calcium antagonist, nitrendipine, on blood pressure and heart rate of conscious, unrestrained dogs.

The acute effects of a single dose of a new calcium-antagonistic vasodilator, 1,4-dihydro-2,6-dimethyl-4-(3-nitrophenyl)-3,5-pyridine carboxylic acid, 3-ethyl-5-methyl ester (nitrendipine, Bay e 50090, on blood pressure and heart rate was examined in conscious dogs by means of a radio-telemetric method. Nitrendipine caused a dose-dependent fall in mean arterial blood pressure of up to 30% in renal hypertensive dogs in a dose range of 0.3-3.15 mg/kg p.o., which was maximal within 2-3 h and was maintained for up to 8 h after a single dose. In normotensive dogs, nitrendipine was somewhat less active. The fall in blood pressure was accompanied by an increase in heart rate, which was less pronounced and less persistent than after administration of hydralazine. Nitrendipine was found about 20 times more potent in its antihypertensive action than hydralazine.