Factors associated with optimized tacrolimus dosing in hematopoietic stem cell transplantation

Objective The primary objective was to analyze the initial tacrolimus concentrations achieved in allogeneic hematopoietic stem cell transplantation patients using the institutional dosing strategy of 1 mg IV daily initiated on day +5. The secondary objectives were to ascertain the tacrolimus dose, days of therapy, and dose changes necessary to achieve a therapeutic concentration, and to identify patient-specific factors that influence therapeutic dose. The relationships between the number of pre-therapeutic days and incidence of graft-versus-host disease and graft failure were delineated. Methods A retrospective chart review included adult allogeneic hematopoietic stem cell patients who received tacrolimus for graft-versus-host disease prophylaxis in 2012. Descriptive statistics, linear and logistic regression, and graphical analyses were utilized. Results Ninety-nine patients met the inclusion criteria. The first concentration was subtherapeutic (<10 ng/ml) in 97 patients (98%). The median number of days of tacrolimus needed to achieve a therapeutic trough was 10 with a median of two dose changes. The median therapeutic dose was 1.6 mg IV daily. Approximately 75% of patients became therapeutic on ≤ 2 mg IV tacrolimus daily. No relationship was found between therapeutic dose and any patient-specific factor tested, including weight. No relationship was found between the number of days of therapy required to achieve a therapeutic trough and incidence of graft-versus-host disease or graft failure. Conclusion An initial flat tacrolimus dose of 1 mg IV daily is a suboptimal approach to achieve therapeutic levels at this institution. A dose of 1.6 mg or 2 mg IV daily is a reasonable alternative to the current institutional practice.