Abstract
Aims: The protective role of calcium channel blockers on renal function has been documented in humans by use of several modalities but renal scintigraphy has however not been used for this purpose. This study was conducted to evaluate the effect of nifedipine a dihydropyridine calcium channel blocker on ^99mTc-DTPA renogram curve.

Methods: A total of 43 subjects, 20 normal and 23 hypertensive under went two ^99mTc-DTPA renal scans under same phvsioloqical conditions, with a three day interval in between, durinq which they took oral nifedipine (dose 10 mg twice daily). All the subjects had normal renal function established by routine laboratory investigations. Renograms from each kidney were generated and were used to calculate differential renal uptake and excretory function parameters of the kidneys. Paired student t-test was applied to check the statistical significance of the difference observed in the various calculated parameters, taking each kidney as an individual study organ.

Results: Quantitative renal function parameters (i.e., GFR, Peak height/mCi and uptake slope) improved significantly after use of nifedipine in both groups. GFR increased by 9.16% in hypertenslve group and 6.14% in normal group (p < 0.05). Peak height/mCi increased by 6.55% in hypertensive group and 5.8% in normal group (p < 0.05). Parenchymal uptake slope increased by 12.6% in hypertensive group and 8.6% in normal group (p < 0.05). T_max reduced by 10.6% in hypertensive group and 11.95% in normal group (p < 0.05). Statistically significant improvement in the renal excretory function parameters was observed only in hypertensive group. T_1/2max decreased by 13.4% (p < 0.05), Parenchyrnal retention index 20/3 and 30/3 improved by 9.6% (p < 0.05) 21.6% (p < 0.05) respectively in hypertensive group. However, no statistically significant change was observed in these parameters in normal group. Target-to-background ratio improved by 10.4 in hypertensive group and 11.5% in normal group (p < 0.05).

Conclusion: Short-term use of nifedipine, even in a small dose, has significant impact on the different quantitative parameters derived from renogram curves. It improved all the quantitative renal uptake and excretory functional parameters in hypertensive subjects. In the normal group, only the parameters related to the uptake function demonstrated a significant improvement.