Pharmacokinetic effect of voriconazole on cyclosporine in the treatment of aspergillosis after renal transplantation.

Azole antifungal agents are essential drugs in the treatment of fungal infections in renal transplant patients. As azoles, these antifungal agents are inhibitors of CYP3A4 and P-glycoprotein (P-gp); and thus therapeutic drug monitoring is important. We evaluated a patient with cutaneous and pulmonary aspergillosis who was successfully treated with voriconazole and a low cyclosporine trough level (3.2 - 27.9 ng/ml) for 3 months. During that period, the patient showed good allograft function with the co-administration of voriconazole and cyclosporine. We measured the patient's genotype of MDR1, CYP3A4, CYP3A5 and CYP2C19 enzymes in addition to the intracellular concentration of cyclosporine in peripheral blood mononuclear cells (PBMCs). The intracellular concentration of cyclosporine in PBMC is 3.2 times higher with no functionally defected alleles in MDR1, CYP3A4, CYP3A5 or CYP2C19 enzymes when cyclosporine is co-administered with voriconazole ex vivo. Although other confounding factors causing immunological modulation may exist, it is plausible that low serum and high intracellular cyclosporine concentrations, due to the inhibition of P-gp activity by voriconazole, also contribute to an immunosuppressive state.