Effectiveness of Empirical Tacrolimus Dosing in Renal Graft Immunosuppression

Introduction: Kidney transplantation remains the most effective therapeutic option for patients with end-stage chronic kidney disease, as it significantly improves survival and quality of life. Long-term graft maintenance requires continuous immunosuppressive therapy, with tacrolimus being one of the cornerstone agents due to its potent properties. However, given its narrow therapeutic index and marked pharmacokinetic variability, regular therapeutic drug monitoring is crucial. In this context, this study aimed to assess the effectiveness of the tacrolimus empirical dose in immunosuppressing renal transplant patients during the first year after transplantation. Methods: A retrospective observational cohort study was conducted, including 58 adult patients who underwent kidney transplantation in 2017 at Ana Nery Hospital in Salvador, Bahia, and received tacrolimus as part of their immunosuppressive regimen. Patients were followed for 12 months post-transplantation, with serial assessments of tacrolimus blood concentrations and renal function markers. Results: Throughout the 12-month follow-up, mean tacrolimus trough concentration remained within the recommended therapeutic range, both before and after each sixth month. Nevertheless, two patients exhibited subtherapeutic levels, with biopsy-confirmed acute rejection episodes. Discussion: Subtherapeutic tacrolimus concentrations are a recognized risk factor for acute rejection and, in this cohort, were associated with significant elevations in serum creatinine among patients with biopsy-proven rejection. These findings underscore the importance of individualized tacrolimus dosing and consistent therapeutic monitoring, accounting for interindividual pharmacokinetic variability, rejection risk, and potential nephrotoxicity – even in the absence of early creatinine alterations. Conclusion: Tacrolimus dosing and adjustment by the nephrology team were generally effective in preventing acute rejection during the first post-transplantation year. Ongoing individualized monitoring remains essential to optimize long-term graft outcomes.