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

The objective of the present study is to clearly evaluate the inhibitory effects of tacrolimus (tacro) on important UGT isoforms in human liver, including determination of inhibition kinetic type and calculation of inhibition kinetic parameters. An in vitro incubation system was used to investigate the inhibitory effect of tacro on UGT isoforms. The recombinant UGT isoforms were used as enzyme source, and a nonspecific substrate 4-methylumbelliferone (4-MU) was utilized as substrate.