Formulas for estimating the initial dosage of tacrolimus for continuous intravenous infusion immediately after pediatric kidney transplantation

Abstract

Background and Purpose: In our department, tacrolimus is administered by continuous intravenous infusion (FK civ) to achieve a blood concentration of 10 ng/mL following pediatric kidney transplantation until oral administration becomes possible. To stabilize blood concentrations after surgery, we developed a formula to estimate the FK civ dosage. Methods: This study included 36 patients (18 males and 18 females) aged <20 yrs. who underwent kidney transplantation at our hospital between January 2016 and August 2023 and received FK civ with blood concentration monitoring. Multivariate analysis was performed using FK civ dosage to achieve a target blood concentration of 10 ng/mL as the dependent variable. Results: The median FK civ dosage was 0.48 mg/day (interquartile range: 0.35–0.64), with a median blood concentration of 12.5 ng/mL (interquartile range: 10.8–15.0). Blood concentrations were measured in 33 patients the day after surgery. The formula for FK civ dosage (mg/day) targeting blood concentration 10 ng/mL is: 1.358 * body surface area (m²)−0.04809 * age (yrs.)−0.27774, with an R² value of 0.38. Conclusion: In the case of FK civ after pediatric kidney transplantation, the formula for FK civ dosage (mg/day) targeting blood concentration 10 ng/mL is: 1.358 * body surface area (m²)−0.04809 * age (yrs.)−0.27774.