Effects of Calcineurin Inhibitors on Sirolimus Pharmacokinetics During Staggered Administration in Renal Transplant Recipients

Study Objective. To compare the effects of different calcineurin inhibitors on sirolimus pharmacokinetics during long-term, staggered administration in kidney transplant recipients. Design. Randomized, open-label, parallel-group trial. Setting. A medical center and one of its teaching hospitals in Taiwan. Patients. Twenty-two de novo kidney transplant recipients. Intervention. Patients received cyclosporine microemulsion or tacrolimus capsules twice/day in combination with once-daily sirolimus solution and corticosteroids. Sirolimus was administered 6 hours after the morning dose of cyclosporine or tacrolimus. After receiving a 6-mg loading dose of sirolimus, participants received sirolimus 2 mg/day for at least 7 days. Neither the cyclosporine nor the tacrolimus dosage was adjusted for at least 3 days before and during blood sampling for pharmacokinetic profiling. Measurements and Main Results. One patient dropped out because of trimethoprim-sulfamethoxazole–related hepatotoxicity. We observed no differences between the two patient groups in terms of their demographic data, renal and liver function, or dosage of sirolimus during the study. During multiple-dose administration, the area under the whole-blood concentration–time curve and the peak and trough concentrations of sirolimus in the cyclosporine group were, respectively, 1.46 (95% confidence interval [CI] 1.21–1.71), 1.42 (95% CI 1.08–1.76), and 1.42 (95% CI 1.09–1.76) times higher than those of the tacrolimus group, even though sirolimus was administered 6 hours after the other agents. Conclusion. Sirolimus pharmacokinetics may change significantly when calcineurin inhibitors are switched, even with staggered administration, which may not completely prevent a drug interaction between cyclosporine and sirolimus solution.