Effective oral administration of tacrolimus in renal transplant recipients

Tacrolimus is usually administered orally based on mg/kg or the trough concentration (Cmin) in whole blood. However, it is not easy to determine the optimal oral dose because of considerable variation of tacrolimus bioavailability between patients. In this study, pharmacokinetics of tacrolimus in various conditioning kidney transplant recipients was investigated.

1) Thirty-three patients were randomly assigned to participate in two groups. In 17 patients, tacrolimus was administered orally after an overnight fast with breakfast given 1 h later, and in the other 16 patients it was administered orally 1 h after breakfast. 2) In 4 patients, the same dose tacrolimus was given after an overnight fast and 0.5 h after breakfast on two consecutive days. 3) Five patients who underwent continuous ambulatory peritoneal dialysis (CAPD) before transplantation were studied. All patients were investigated in daily profile of tacrolimus blood levels.

There was a strong correlation between area under the curve (AUC) and the trough concentration in both preprandial and postprandial oral administration, with correlation coefficients of 0.838 and 0.860, respectively. Significant increases in the peak concentration (Cmax) and AUC were observed in the preprandial oral administration subjects. Absorption of CAPD patients was obviously insufficient.

Since tacrolimus absorption was better under fasted condition than under the presence of food, it is thought that the highest medicine effect with the least dosage is provided by preprandial oral administration. Furthermore, preprandial oral administration is recommended from a respect of economic burden reduction and side effect reduction.