A proposal of FK506 optimal dosing in living related liver transplantations.

We analyzed the relation between FK506 trough levels (ELISA: patients 1-41, IMx: patients 42-70) and rejection and/or viral infection episodes, retrospectively, in the first 70 consecutive cases of living related liver transplantation. Twenty patients (28.6%) had rejection episodes. Of the 13 patients who had evidence of rejection during the first 3 months, 6 patients without infection and 7 patients with viral infection showed low concentrations of FK506 (< 5 ng/ml). Twelve patients were treated and improved with high dose steroid administration and an increase in the FK506 dosage. One patient died of refractory rejection. Nine patients had evidence of rejection after the first 3 months. In 3 patients, weaning from FK506 initiated the rejection episodes. Five patients repeated rejection and 4 patients required a third immunosuppressant (azathioprine). Viral infection included CMV (11 cases), EBV (13 cases), HZV (3 cases), and HSV (1 case). Excess immunosuppression might have been the cause, but no clear correlation was found. We propose that the optimal dosage of FK506 obtained by monitoring the trough levels using the IMx method should maintain a 10-20 ng/ml level during the first month, and a 5-10 ng/ml level at the second and third months.