POTENTIAL INTERACTION OF TROGLITAZONE AND CYCLOSPORINE

Background. Troglitazone (Rezulin) is a promising new oral hypoglycemi c agent recently approved by the Federal Drug Administration for use i n type II diabetes mellitus. Although troglitazone is not metabolized by the cytochrome p450 3A isozyme family, it is a potential inducer of this system, Other medications, e.g., rifampin and phenobarbital, whi ch also induce p450 3A activity, have been reported to significantly d ecrease cyclosporine (CsA) concentrations. Methods. We report a case o f a stable renal transplant patient who had a decrease in CsA concentr ation after beginning troglitazone and who subsequently developed an a cute rejection episode. We then reviewed all stable renal patients beg un on troglitazone over the previous 6 months. Results. The seven tran splant patients who had been started on troglitazone therapy experienc ed a statistically and clinically significant decrease in CsA 12-hr tr ough levels immediately after the institution of troglitazone therapy. Conclusion. A potential interaction exists between troglitazone and C sA. Transplant patients on CsA who receive troglitazone therapy should be monitored closely.