Tacrolimus strongly inhibits multiple human UDP-glucuronosyltransferase (UGT) isoforms

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Quantification of the Immunosuppressant Tacrolimus on Dried Blood Spots Using LC-MS/MS
08:38

Quantification of the Immunosuppressant Tacrolimus on Dried Blood Spots Using LC-MS/MS

Published on: November 8, 2015

Xiao-You Liu1, Zhong-Ze Fang, Pei-Pei Dong

  • 1Department of Organ Transplantation, Zhujiang Hospital, Nanfang Medical University, Dalian, China.

Die Pharmazie
|September 29, 2012
PubMed

Insights

Tacrolimus (tacro) strongly inhibits key human liver UDP-glucuronosyltransferase (UGT) enzymes, including UGT1A1, UGT1A3, UGT2B7, and UGT2B15. This inhibition may explain frequent drug-drug interactions observed with tacrolimus.

Area of Science:

  • Pharmacology
  • Drug Metabolism
  • Enzyme Kinetics

Background:

  • Tacrolimus (tacro) is an immunosuppressant with a narrow therapeutic index.
  • Drug-drug interactions (DDIs) involving tacrolimus are clinically significant.
  • UDP-glucuronosyltransferases (UGTs) are crucial enzymes in drug metabolism.

Purpose of the Study:

  • To evaluate the inhibitory effects of tacrolimus on major human liver UGT isoforms.
  • To determine the inhibition kinetics and parameters for tacrolimus-induced UGT inhibition.

Main Methods:

  • In vitro incubation system using recombinant UGT isoforms.
  • 4-methylumbelliferone (4-MU) as a nonspecific substrate.
  • Dixon and Lineweaver-Burk plots for kinetic analysis.

Main Results:

  • Tacrolimus exhibited concentration-dependent inhibition of UGT1A1, UGT1A3, UGT2B7, and UGT2B15.
  • Competitive inhibition was observed for UGT1A1, UGT1A3, and UGT2B7.
  • Noncompetitive inhibition was observed for UGT2B15.
  • Inhibition kinetic parameters (Ki) were determined for each UGT isoform.

Conclusions:

  • Tacrolimus significantly inhibits critical human liver UGT isoforms.
  • The observed inhibition patterns provide mechanistic insight into tacrolimus-related DDIs.
  • Understanding these interactions is vital for optimizing tacrolimus therapy and patient safety.

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