SCINTIGRAPHIC EVALUATION OF THE SHORT-TERM AND LONG-TERM RENAL EFFECTS OF ORAL FELODIPINE USING TECHNETIUM-99M-MERCAPTOACETYL TRIGLYCINE

The short- and long-term effect of felodipine on renal perfusion and t ubular function was investigated using a new renal tubular imaging age nt, Tc-99m-mercaptoacetyl triglycine (Tc-99m-MAG3). Twelve patients wi th essential hypertension (mean age = 49 +/- 8 years) were studied. Re nal scintigraphies with 180 MBq Tc-99m-MAG3 were performed at baseline , at the 2nd hour following oral administration of 5 mg felodipine and 4 weeks later on 5-10 mg daily felodipine therapy. The time-activity curves of each kidney were obtained following background subtraction. The Tc-99m-MAG3 clearance value was measured for each kidney. In addit ion, perfusion index (PI), reno index, time to maximum, half-maximum a nd two thirds of maximum activity values of each kidney were calculate d. Systolic and diastolic blood pressures were significantly lowered w ith long-term administration of felodipine (from 159 +/- 12/105 +/- 5 to 141 +/- 11/87 +/- 7 mm Hg, p = 0.01 and p = 0.002, respectively). H eart rate did not change significantly. Initially, a decrease in PI in dicating an increase in renal blood flow (from 246 +/- 96 to 194 +/- 5 4, p = 0.01) was observed, whereas no change was noted during the chro nic administration (to 230 +/- 69, p = NS). Total clearance of Tc-99m- MAG3 was decreased nonsignificantly following the initial dose of felo dipine (from 361 +/- 93 to 351 +/- 91 ml/min, p = NS). During long-ter m therapy, felodipine did not alter the perfusion and tubular function of the kidneys. Our results indicated that felodipine causes a signif icant increase in renal blood flow initially, even with a nonsignifica nt change in systemic blood pressure.