Abstract: Objective: To investigate the best application and the ideal blood concentration of FK506 after liver transplantation in infants. Methods: From September 2006 to November 2009,13 infants received liver transplantation in Center of East Organ Transplantation, First Central Hospital of Tianjin, including 8 living donor liver transplantations and 5 split liver transplantations. Corticosteroids were applied intra-operatively, and the FK506-based immunosuppressive therapy was used after the operation. The dosage and blood concentration of FK506 were monitored within 3 months, 3 months to 1 year, 1 year postoperatively, except for the FK506-related complications. Results: All of the patients were followed up 3 to 40 months (median 18 months), 11 cases of them were still alive, 2 cases died. The blood concentrations of FK506 within 3 months, 3 months to 1 year, 1 year after operation were （8.64±3.71）ng?ml-1,（7.90±2.76）ng?ml-1 and（5.38±1.73）ng?ml-1, while the dosages were (0.21 ± 0.12) mg ? kg-1 ? d-1, (0.18 ± 0.08) mg ? kg-1 ? d-1 and (0.11 ± 0.03) mg ? kg-1 ? d-1. The FK506-related complications postoperatively included acute rejection in 2 cases, infections in 12 man-times, FK506-related psychotic symptoms in three cases. Conclusion: The blood concentration of FK506 after liver transplantation in infants should be maintained at the appropriate level, and the dosage adjustments should be based on the concentration of FK506, so as to minimize the side effects of FK506 caused by insufficient or excessive amount.

Key words: Liver Transplantation, Infants, FK506