Pharmacokinetics of Different Tacrolimus Formulations in the Early Post-Liver Transplant Period: A Scoping Review.

Abstract

<b>Background:</b> Tacrolimus (TAC) is the cornerstone of immunosuppression after liver transplantation (LT). TAC has a narrow therapeutic index and high inter- and intra-individual pharmacokinetic (PK) variability, requiring dose individualization. This variability is more noticeable in the early post-LT period. <b>Objectives:</b> This study aimed to compare the PK of different TAC formulations in the early post-LT period and describe the main PK characteristics and plasma levels obtained with each TAC formulation used. <b>Methods:</b> The search was conducted in MEDLINE (PubMed) and EMBASE in accordance with PRISMA-ScR guidelines. The main inclusion criteria were clinical trials and observational studies focusing on the PK parameters of TAC in LT recipients during the first month post-transplant. <b>Results:</b> A total of 2169 articles were identified, of which 23 met the inclusion criteria. Various PK parameters were analyzed after LT for the different TAC formulations: intravenous (iv) and oral forms, such as immediate-release (IRT), prolonged-release (PRT), and extended-release (LCPT) formulations. PK variability was higher in the initial days after LT, with different TAC exposure between formulations. IV TAC allows the rapid attainment of therapeutic levels, but it has fallen into disuse. Regarding oral formulations, IRT reaches target levels faster than PRT and LCPT. PRT and LCPT exposure seem more stable during the first month post-LT than when using IRT. <b>Conclusions:</b> TAC formulations exhibit relevant differences in their PK profile in the early post-LT period. PK differences might influence the dose regimen and the time to achieve PK targets. Given these variations, therapeutic drug monitoring (TDM) is essential for optimizing treatment.