Estellés A., Lapunzina P., Borobia AM., Carcas AJ., Effect of the CYP3A5, CYP3A4, CYP3A7, ABCB1, POR and NR1I2 genes in the pharmacokinetics of tacrolimus in a pediatric cohort with stable serum concentrations after renal transplantation: study protocol. IBJ Clin Pharmacol 2017 1(1):e0005. Funding: The authors have no financial relationships relevant to this article to disclose. Competing Interests: The authors have no financial relationships relevant to this article to disclose BACKGROUND: Therapeutic response to pharmacological therapy in humans shows large intrapatient and interpatient variability both in treatment efficacy and adverse drug reactions (ADR). Part of this variability can be explained by genetic polymorphisms in genes encoding TAC metabolism related proteins. The aim of this study is to evaluate the contribution of genetic variation in the CYP3A4, CYP3A5, CYP3A7, POR, NR1I2 and ABCB1 genes to this variability in order to achieve a better understanding of TAC pharmacokinetics and a more personalized approach for TAC dosing in a cohort of pediatric patients with stable serum concentrations after renal transplantation.