Acute cyclosporine A nephrotoxicity in a renal allograft recipient with hypothyroidism.

Cyclosporine A (CsA) is an important immunosuppressant in kidney transplantation. Acute CsA nephrotoxicity secondary to high drug levels is a well-recognized complication in the immediate posttransplant period. Cyclosporine A is metabolized in the body by the hepatic cytochrome P-450 enzyme system. We present a case of a hypothyroid patient who developed toxic blood CsA levels and acute nephrotoxicity with standard doses of CsA. A reduction of CsA levels led to an improvement of allograft function. Correction of the hypothyroid state resulted in the normalization of CsA requirements, but overcorrection led to an increased requirement of CsA. Thyroid dysfunction should be considered as an interacting factor in the metabolism of CsA.