Effects of Age and Sex on the Pharmacokinetics of Tacrolimus during Pediatric Kidney Transplantation: A Single Center Study

ABSTRACT

PURPOSE: The pharmacokinetics of tacrolimus, one of the most widely used immunosuppressive drugs, are known to vary by sex, age, and ethnicity during pediatric transplantation. This study assessed the pharmacokinetic characteristics and associated factors of tacrolimus in Korean children receiving a kidney transplant. METHODS: We retrospectively reviewed the pharmacokinetic data (therapeutic dose, trough level, clearance, and half-life) of 9 children who were given tacrolimus as one of their initial immunosuppressive drugs after kidney transplantation. In addition, we compared the findings to data from 10 adult kidney transplant recipients. RESULTS: The mean age of our pediatric patients was 13.9 years, and the male-to-female ratio was 45. The mean dose of tacrolimus was 0.19+/-0.14 mg/kg/day. The mean dose of tacrolimus for males was 0.23+/-0.12 mg/kg/day, which was significantly higher than the dose for females (0.16+/-0.14 mg/kg/day). The trough level was not significantly different between both groups. The clearance rate of tacrolimus for males was also significantly higher than females. Although the dosage of tacrolimus for patients over the age of 12 years was lower (0.18+/-0.13 vs. 0.21+/-0.16 mg/kg/day) and the trough level was higher (8.2+/-4.5 vs. 7.2+/-4.2 mg/mL) than that for patients under the age of 12 years, there was no significant difference between them. However, there were significant differences between children and adults in dose, clearance, and half-life of tacrolimus. CONCLUSION: Out study suggests that the pharmacokinetics of tacrolimus tends to vary with sex and age. Therefore, large-scale prospective studies are required to verify the proper therapeutic dosage of tacrolimus in Korean children.