Acute renal effects of oral felodipine in normal man.

The acute renal effects of a single oral dose of felodipine 0.15 mg/kg were studied in 8 healthy males. Thirty minutes after administration the mean plasma concentration was 25.7 nmol/l. There was a significant reduction in diastolic blood pressure (24%) and a concomitant rise in heart rate (38%), leaving the systolic pressure unchanged. Glomerular filtration rate (GFR) and renal plasma flow (RPF) were measured by the constant infusion technique using the clearance of 125I-iothalamate and 131I-hippuran respectively. GFR was unchanged and the filtration fraction (FF) was reduced, whilst there was a decrease in renal vascular resistance (RVR). The glomerular filter characteristics were unchanged, as estimated by the unchanged excretion rate of albumin. There was a significant rise in the clearance of sodium (176%) but only a small and insignificant increase in urine volume. Clearance of potassium was decreased. An increase in the clearance of uric acid and a rise in the beta-2-microglobulin excretion rate were found, both suggesting a proximal tubular effect of felodipine. The excretion rate of calcium was increased.