Pharmacokinetic analysis of cyclosporine in a renal transplant recipient with congenital absence of the portal vein

Here we report therapeutic drug monitoring of cyclosporine in a kidney transplant recipient lacking enterohepatic circulation. The patient developed steroid‐resistant nephrotic syndrome at age 14 years, and was medicated with an oral cyclosporine microemulsion. However, her cyclosporine trough level was unexpectedly elevated, and subsequent investigations showed that she was deficient in drug metabolism as a result of the congenital absence of the portal vein. Her renal function gradually decreased and she became dialysis‐dependent at the age of 21 years, and kidney transplantation was planned. Based on pretransplant therapeutic drug monitoring, we started cyclosporine microemulsion at half of the conventional dosage. After transplantation, the dosage was successfully adjusted to achieve a target trough level. The post‐transplant course was stable with no symptoms of rejection or cyclosporine‐associated nephrotoxicity.