Renal effects of nicardipine in essential hypertension: differences between acute and chronic therapy

Previous reports have described improvements in renal function with acute administration of nicardipine. The purpose of this study was to determine if these improvements persist with continued treatment. Using single dose radio-isotopic techniques in six subjects with essential hypertension, evaluations of glomerular filtration rate and effective renal plasma flow were made prior to treatment during an intravenous nicardipine infusion of 80 micrograms/kg per h, and following 6 weeks of treatment with 30-40 mg, three times a day. Subjects were stabilized on a diet containing 100 mmol Na+, 80 mmol K+ and 1650 ml water. Blood pressure was similarly reduced with both acute (-45/26 mmHg) and chronic (-42/21 mmHg) therapy. Renal vascular resistance index fell with both acute (-39%) and chronic (-26%) treatment. Significant increases in effective renal plasma flow (+15%), urine volume (+121%), and urinary sodium (+168%) and calcium (+128%) elimination were seen with acute treatment. These parameters had returned to control levels after 6 weeks of treatment. No change was seen in glomerular filtration rate, filtration fraction, plasma renin activity or plasma aldosterone concentration. These data showed that the natriuresis and diuresis as well as the increase in effective renal plasma flow seen with the introduction of nicardipine therapy, did not persist during long-term treatment. There was no evidence of deterioration in any aspect of renal function during long-term therapy despite the significant reduction in renal perfusion pressure.