Targeted blood levels of cyclosporin for cardiac transplantation.

Forty-nine patients have undergone cardiac transplantation since July, 1982, and have been treated with maintenance cyclosporin and low-dose prednisone, 15 to 20 mg. Cyclosporin dose has been targeted to a whole-blood level of 1,000 ng/ml as measured by radioimmune assay. The actuarial survival rate in this group of patients has been 79% at 12 months and 71% at 21 months. Histologic rejection has occurred at all blood levels of cyclosporin, as has significant nephrotoxicity. The hepatic toxicity encountered has been more a clinical nuisance than significant problem. The administered dose of cyclosporin required to reach a target of 1,000 ng/ml has varied between 2 and 30 mg/kg/day. The average perioperative and late serum creatinine levels were 1.2 and 1.49 mg/dl and occurred with cyclosporin levels of 1,078 and 1,068 ng/ml, respectively. Late cyclosporin toxicity has persisted despite reduction in the dose of cyclosporin below the targeted 1,000 ng/ml. Some method of blood level monitoring is necessary in patients receiving cyclosporin immune suppression to assure adequacy of the administered dose. The 1,000 ng/ml target has provided adequate immune suppression. Significant nephrotoxicity has not correlated with the blood level measured.