The effect of nicardipine on blood pressure, its variability and reflex cardiac control.

Eight untreated patients with essential hypertension (average casual blood pressure 180/110 +/- 27/12 mm Hg) were studied following control, acute (a single oral dose of 30 mg nicardipine hydrochloride), and chronic (2 months nicardipine oral therapy) treatment periods. During the 2 month treatment period, ambulatory mean intra-arterial (IABP), measured when the patients were awake, fell from 165/105 +/- 6/12 (control) to 150/96 +/- 14/12 mm Hg (P less than 0.05), but heart rate remained unchanged (84 +/- 12 control vs 80 +/- 9 beats min-1). There was an absolute reduction in blood pressure in response to tilting, the Valsalva manoeuvre, and exercise handgrip, but the percent increase in pressure following nicardipine was not significantly different from that in the control period. There was no change in baroreflex sensitivity after either acute or chronic treatment, but the set point of the reflex was reset to a lower pressure following chronic therapy. Both single and multiple doses of nicardipine significantly reduced intra-arterial pressure. Chronic therapy was associated with return of the heart rate to control values, which was due to resetting of the baroreflex control mechanism.