Tacrolimus is an immunosuppressant that exerts its activity via suppression of cellular immunity by binding to FKBP-12 to form a complex with calcineurin-dependent proteins to inhibit calcineurin phosphatase activity and subsequently T lymphocyte activation. Approved by the Federal Drug Administration (FDA) under the brand name Prograf ® in 1994, immediate-release tacrolimus (IR-TAC) is now considered the backbone of maintenance immunosuppressive regimens in solid organ transplantation (SOT). In the United States (US), it is reported that more than 70% of SOT recipients are initiated on a TAC-based regimen (SRTR 2018 Annual Report). The extensive use of tacrolimus is likely attributable to its superiority in prevention of allograft rejection, particularly in the