Trofe-Clark J, et al. - Researchers performed this study to advance understanding of the differences in tacrolimus exposure between African American CYP3A5 expressers and CYP3A5 nonexpressers using steady-state 24-hour pharmacokinetic profiling and to explore the hypothesis that pharmacogenetic differences between CYP3A5 expressers and nonexpressers would be attenuated by delayed tacrolimus absorption with LifeCycle Pharma Tac [LCPT] compared to immediate absorption with immediate-release tacrolimus (IR-Tac). In most African Americans, achieving therapeutic tacrolimus trough concentrations with IR-Tac resulted in marked higher peak concentrations, potentially magnifying the risk for toxicity and adverse outcomes. Delayed tacrolimus absorption with LCPT would reduce this pharmacogenetic effect.