Recommended in vitro substrates and inhibitors of UGTs

UGTSelective Substrates KmSelective InhibitorRecommended Inhibitor Concentration Range (reported IC50 value)References
1A1UGT1A1: 17β-estradiol (3-glucuronide formation) (11, 170b)Atazanavir0.01–20 (UGT1A1 IC50 = 0.31a)Lepine et al., 2004; Zhang et al., 2005; Itäaho et al., 2008;Walsky et al., 2012; Seo et al., 2014
1A3UGT1A3: 17β-estradiol (3-glucuronide formation) (250) (17-glucuronide formation) (67)Lithocholic acid0.01–20 (UGT1A3 IC50 = 7.9)Lepine et al., 2004; Zhang et al., 2005; Itäaho et al., 2008; Walsky et al., 2012; Seo et al., 2014
1A4Trifluoperazine (42, 67b)Hecogenin0.02–20 (IC50 = 1.5a)Uchaipichat et al., 2006a; Walsky et al., 2012;
1A65-Hydroxytryptophol (420, 330b)Troglitazone0.1–100 (IC50 = 28)Ito et al., 2001; Krishnaswamy et al., 2004; Walsky et al., 2012
1A9Propofol (98, 46b)Digoxin0.1–100 (IC50 = 1.7) bVietri et al., 2002; Lapham et al., 2012
Niflumic acid0.01–100 (IC50 = 0.3a)Bernard and Guillemette, 2004
Transilast0.1–100 (IC50 = 0.7)bCourt, 2005; Mano et al., 2006
2B7Zidovudine (586, 150b, 77c)β-Phenyllongifolol-20.001–1 (IC50 = 0.006)Bichlmaier et al., 2007; Manevski et al., 2011; Lapham et al., 2012; Walsky et al., 2012
  • a The University of Washington Metabolism and Transport Drug Interaction Database ( was queried in the category of “In vitro Parameters” for studies providing Km values for the indicated substrates or Ki or IC50 values for the indicated precipitants. If individual Ki or IC50 values were listed for one study, the average was taken. If a range of values were given, the lowest value was taken. Median value was derived across all reported values. All queries were of data reported in the Database as of Dec 2015.

  • b In the presence of 2% BSA.

  • c In the presence of 1% BSA.