Clinical Impact of Tacrolimus Intrapatient Variability on Graft Outcomes in Kidney Transplant Recipients: A Review

Tacrolimus is one of the most commonly used immunosuppressive agents for the prevention of graft rejection following transplantation.Despite its effectiveness, its clinical application is complicated by a narrow therapeutic window and significant pharmacokinetic variability. In recent times, tacrolimus intrapatient variability (IPV)—that is, variability in tacrolimus trough concentration in the same patient—has emerged as a significant predictor of transplant problems. In this review, we have discussed the pharmacological profile of tacrolimus, methods used for calculating tacrolimus IPV, and various factors that affect IPV and its clinical significance in renal transplant donors. Tacrolimus acts by binding to FK-binding protein 12 and thereby inhibiting calcineurin. This leads to inhibition of T-cell activation, which is essential for T-cell proliferation, thereby reducing immune-mediated responses. The cytochrome P450 enzymes CYP3A4 and CYP3A5 are responsible for the metabolism of tacrolimus.Various factors affect tacrolimus exposure, which include differences in ethnicity, drug-drug interactions, gastrointestinal upsets, hepatic impairment, and patient compliance with treatment. IPV is generally calculated by using statistical methods such as measures of variation, standard deviation, and mean absolute deviation of trough attention. Most commonly, it is calculated by using the coefficient of variance. Clinical trials have confirmed that a high IPV is related to situations like acute kidney rejection, confirmation of donor-specific antibodies, routine graft harm, reduced graft survival, and reduced renal function. Non-adherence to the remedy, pharmacogenetic factors like CYP3A5 polymorphism, drug interactions, and so on are critical causes of IPV.