Tacrolimus is an immunosuppressive agent administered to transplant recipients to prevent and treat allograft rejection. Clinical use of tacrolimus is complicated by its high inter-patient variability in pharmacokinetics and a narrow therapeutic index. As a result, management of tacrolimus usually includes therapeutic drug monitoring (TDM). Concentrations of tacrolimus are strongly influenced by CYP3A5 genotype - individuals with the CYP3A5 *1/*1 or CYP3A5 *1/*3 genotype (also known as extensive and intermediate metabolizers, respectively) have significantly lower concentrations of tacrolimus as compared to those with the *3/*3 genotype (poor metabolizers). In addition to standard TDM, adjusting the starting dose of tacrolimus based on CYP3A5 genotype may allow for a more rapid achievement of therapeutic drug concentrations.
For details, see the CPIC guideline on PharmGKB.
For other CPIC guidelines see the list of CPIC publications and guidelines in progress.