ANTIHYPERTENSIVE EFFECT OF AMLODIPINE AND LACK OF INTERFERENCE WITH CYCLOSPORINE METABOLISM IN RENAL-TRANSPLANT RECIPIENTS

The catabolism of various calcium channel blockers through cytochrome P-450 is heterogeneous and may be modified by concomitant use of cyclosporin A. In an open study we investigated the antihypertensive effect and clinical tolerance of the dihydropyridine amlodipine and its effects on cyclosporine kinetics in stable hypertensive renal transplant recipients not taking corticosteroids. Ten adult hypertensive patients grafted for 21.4+/-8.9 months and well stabilized with normal renal function were included in the study. Renal artery stenosis was ruled out by normal Doppler echography. After 2 weeks of placebo, amlodipine was started at a daily dose of 5 mg. The dose was then adjusted to 10 mg if necessary. Blood and urine chemistries and whole-blood cyclosporine trough levels were measured weekly. Cyclosporine kinetics were determined on a hourly basis before amlodipine administration and after 4 weeks of treatment. Normal blood pressure was obtained with the use of 5 mg/d amlodipine in 7 patients and 10 mg/d in 3, diastolic blood pressure decreasing from 98.7+/-3.8 to 81.3+/-9.1 mm Hg (P=.0007). Heart rate slightly increased by 10% (P<.02). The drug was well tolerated, and only minor ankle edema was found in 3 patients. Cyclosporine doses were not modified and cyclosporine levels remained unchanged throughout the study. Cyclosporine kinetic parameters were not significantly different at the beginning and end of the study. Bioequivalence was demonstrated indicating that cyclosporine biotransformation was not altered by the concomitant administration of amlodipine. We conclude that amlodipine at the dosage of 5 to 10 mg/d is an efficient calcium channel blocker in hypertensive renal transplant recipients treated with cyclosporine without corticosteroids. Moreover, amlodipine does not interfere with cyclosporine diffusion and metabolism.