Microsoft Word - NEF658BF

Dr. Y. Pirson, Cliniques Universitaires St. Luc, Department of Nephrology, Avenue Hippocrate 10, B-1200 Brussels (Belgium) Dear Sir, Calcium channel blockers are increasingly used in kidney graft recipients not only to lower blood pressure but also to prevent or attenuate ischemia or ciclosporin (CS)-induced graft dysfunction [1–3]. Their usefulness however is limited by a potentially deleterious interaction with CS metabolism. Indeed increased CS trough levels with an attendant nephrotoxi-city have been reported in transplant recipients given calcium channel blockers, probably as the result of an altered CS hepatic metabolism. This effect is observed only with selected calcium channel blockers such as diltiazem [4, 5], verapamil [6] and nicardipine [7, 8] but not with others such as nifedipine [9] and nitrendipine [10]. Detailed information should thus be available for each new calcium channel blocker introduced in the treatment of patients receiving CS. In this presentation we examine the potential interaction between CS and isradipine, a secondgeneration calcium channel blocker of the 1,4-dihydropyridine group [11] for which no such information is yet available. After informed consent, 7 hypertensive transplant recipients with a stable graft function and a constant CS dosage were given isradipine 5 mg daily (in 2 doses) for at least 2 weeks. In 4, isradipine replaced nifedipine; in the other 3 no calcium channel blocker had been given. During the study, all other drugs remained unchanged. Serum creatinine, urea and CS trough levels were recorded before and 2 weeks after the initiation of isradipine treatment. CS was given daily in a single morning dose. Serum trough levels were measured by fluorescence-polarization immunoassay (nonspecific poly-clonal antibody, Abbott) after 2 h equilibration of the blood sample at room temperature. As shown in table 1, Table 1. CS dose, renal function and CS level before and after 2-week isradipine treatment (means ± SD) CS dose Serum Serum Serum CS mg/kg creatinine urea trough level mg/dl mg/dl ng/ml Before 4.6 ± 1 1.26 ± 0.3 39 ± 13 34.5 ± 21