AUTHOR=Piletta-Zanin Alexandre , De Mul Aurélie , Rock Nathalie , Lescuyer Pierre , Samer Caroline F. , Rodieux Frédérique 

TITLE=Case Report: Low Hematocrit Leading to Tacrolimus Toxicity

JOURNAL=Frontiers in Pharmacology

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/pharmacology/articles/10.3389/fphar.2021.717148

DOI=10.3389/fphar.2021.717148

ISSN=1663-9812

ABSTRACT=<p>Tacrolimus is a calcineurin inhibitor characterized by a narrow therapeutic index and high intra- and inter-individual pharmacokinetic variability. Therapeutic drug monitoring in whole-blood is the standard monitoring procedure. However, tacrolimus extensively binds to erythrocytes, and tacrolimus whole-blood distribution and whole-blood trough concentrations are strongly affected by hematocrit. High whole-blood tacrolimus concentrations at low hematocrit may result in high unbound plasma concentrations and increased toxicity. We present the case of a 16-year-old girl with kidney and liver transplant in whom low concentrations of tacrolimus in the context of low hematocrit led to significant increase in the dosage of tacrolimus and participate, along with a genetic polymorphism of <italic>ABCB1</italic>, in nephrotoxicity.</p>