2021년 Vol.38 No.02
Background : Tacrolimus is an immunosuppressive agent and is largely used to prevent graft-versus-host disease in hematopoietic stem cell transplantation patients. Tacrolimus requires therapeutic drug monitoring because of its narrow therapeutic range. The number of cases where the dose of tacrolimus was reduced in obese patients because the blood concentration was higher than the initial effective therapeutic range (10–15 ng/mL)is increasing. Therefore, this study attempted to assess the adequacy of early tacrolimus dosages and establish more suitable weight-based dosing strategies for obese patients.
Methods : This was a retrospective study, conducted on patients 20 years of age or older who received tacrolimus from the day before transplantation from January 2019 to June 2020 in Seoul St. Mary’s Hospital. The blood concentration of tacrolimus in the actual body weight (ABW) group was obtained from the actual blood collection, from which patient-specific pharmacokinetic parameters were obtained. The expected blood concentration of tacrolimus in the ideal body weight (IBW) group was then calculated. To evaluate the adequacy of the tacrolimus dosage, the average blood concentration and the number of patients within the effective therapeutic range were investigated. To evaluate the risk of developing side effects and the reduction in therapeutic effects, the number of patients above and below the effective therapeutic range and their average tacrolimus level were compared based on ABW and IBW, respectively.
Results : The average blood concentration of 74 patients was 18±5.7 ng/mL in the ABW group and 14±4.5 ng/mL in the IBW group (p<0.001). The number of patients within the effective therapeutic range was 22 (29.7%) in the ABW group and 35 (47.3%) in the IBW group (p=0.043). The number and average tacrolimus level of the patients above the effective therapeutic range were 50 (67.6%) and 20.6±5.1 ng/mL, respectively, in the ABW group and 25 (33.8%) and 19.1±3.5 ng/mL, respectively, in the IBW group. The number and the average tacrolimus level of patients below the effective therapeutic range were 2 (2.7%) and 8.8±0.7 ng/mL, respectively, in the ABW group and 14 (18.9%) and 8.7±1.0 ng/mL, respectively, in the IBW group. There was no statistical difference in the average tacrolimus levels of the patients above and below the effective therapeutic range (p=0.190 and p=0.908, respectively).
Conclusion : In obese patients, the administration of tacrolimus based on IBW is more preferred than ABW-based administration. However, additional pharmacokinetic model studies are needed.