Hemodynamic effects of acute and prolonged administration of nitrendipine in essential hypertension

In six hospitalized subjects with mild or moderate and untreated essential hypertension, we measured mean blood pressure (MBP, brachial artery catheter), heart rate (HR, electrocardiogram), cardiac output (CO, thermodilution), and total peripheral resistance (TPR, MBP divided by CO) at rest and during a cold pressor test (CPT, 60 s), a handgrip exercise (HG, 40% maximum strength for 90 s), and a cyclette exercise (CE, 50 W for 5 min). The study was performed in a no-drug condition, 1 h after 20 mg oral nitrendipine (aN) and 1 week after daily administration of 20 mg oral nitrendipine (pN). Compared with the no-drug condition, aN reduced resting MBP from 137.3 ± 7.3 (mean ± SEM) to 112.3 ± 9 mm Hg (p <0.05), increased resting HR from 72.3 ± 6.9 to 85.3 ± 8.8 beats/min) (p <0.05), increased resting CO from 6,191 ± 508 to 8,700 ± 1,050 ml/min (p <0.05), and reduced resting TPR from 1,807 ± 119 to 1,140 ± 228 dynes/s/cm⁵ (p <0.05). The reduction in resting MBP and TPR were unchanged by pN, whereas the increase in HR and CO were attenuated by 47 and 42%, respectively (p <0.05). Neither aN nor pN altered the hemodynamic responses to CPT, HG, and CE. As a result, the peak MBP and TPR values that were measured during these maneuvers were always lower (p <0.05) during aN and pN than in the no-drug condition. Thus, nitrendipine exerts marked antihypertensive and vasodilatatory effects that are evident at rest and during conditions elevating BP. These effects do not fade with the prolonged administration of the drug. This administration, however, attenuated the reflex cardiac stimulation initially induced by nitrendipine.