Pharmaceutical Research

, 26:1073 | Cite as

Relative Importance of Intestinal and Hepatic Glucuronidation—Impact on the Prediction of Drug Clearance

  • Helen E. Cubitt
  • J. Brian Houston
  • Aleksandra GaletinEmail author
Research Paper



To assess the extent of intestinal and hepatic glucuronidation in vitro and resulting implications on glucuronidation clearance prediction.


Alamethicin activated human intestinal (HIM) and hepatic (HLM) microsomes were used to obtain intrinsic glucuronidation clearance (CLint,UGT) for nine drugs using substrate depletion. The in vitro extent of glucuronidation (fmUGT) was determined using P450 and UGT cofactors. Utility of hepatic CLint for the prediction of in vivo clearance was assessed.


fmUGT (8–100%) was comparable between HLM and HIM with the exception of troglitazone, where a nine-fold difference was observed (8% and 74%, respectively). Scaled intestinal CLint,UGT (per g tissue) was six- and nine-fold higher than hepatic for raloxifene and troglitazone, respectively, and comparable to hepatic for naloxone. The remaining drugs had a higher hepatic than intestinal CLint,UGT (average five-fold). For all drugs with P450 clearance, hepatic CLint,CYP was higher than intestinal (average 15-fold). Hepatic CLint,UGT predicted on average 22% of observed in vivo CLint; with the exception of raloxifene and troglitazone, where the prediction was only 3%.


Intestinal glucuronidation should be incorporated into clearance prediction, especially for compounds metabolised by intestine specific UGTs. Alamethicin activated microsomes are useful for the assessment of intestinal glucuronidation and fmUGT in vitro.


clearance prediction glucuronidation intestine 



intrinsic clearance


intrinsic clearance corrected for non-specific protein binding


intrinsic clearance by glucuronidation


intrinsic clearance by cytochrome P450 metabolism


fraction metabolised by glucuronidation


fraction unbound from protein in the incubation


fraction unbound in the blood


fraction unbound in the plasma


human intestinal microsomes


human liver microsomes


root mean squared error


blood to plasma concentration ratio


uridine diphosphate glucuronosyltransferase



The Authors would like to thank Sue Murby and Dr David Hallifax (University of Manchester) for valuable assistance with the LC-MS/MS.

The work was funded by a consortium of pharmaceutical companies (GlaxoSmithKline, Lilly, Novartis, Pfizer and Servier) within the Centre for Applied Pharmacokinetic Research at the University of Manchester. Part of this study was presented at the 10th ISSX Meeting, May 18–21, 2008, Vienna, Austria.


  1. 1.
    J. O. Miners et al. In vitro–in vivo correlation for drugs and other compounds eliminated by glucuronidation in humans: pitfalls and promises. Biochem. Pharmacol. 71(11):1531–1539 (2006). doi: 10.1016/j.bcp.2005.12.019.PubMedCrossRefGoogle Scholar
  2. 2.
    J. A. Williams et al. Drug–drug interactions for UDP-glucuronosyltransferase substrates: a pharmacokinetic explanation for typically observed low exposure (AUCi/AUC) ratios. Drug Metab. Dispos. 32(11):1201–1208 (2004). doi: 10.1124/dmd.104.000794.PubMedCrossRefGoogle Scholar
  3. 3.
    J. B. Houston. Utility of in vitro drug metabolism data in predicting in vivo metabolic clearance. Biochem. Pharmacol. 47(9):1469–1479 (1994). doi: 10.1016/0006-2952(94)90520-7.PubMedCrossRefGoogle Scholar
  4. 4.
    R. J. Riley, D. F. McGinnity, and R. P. Austin. A unified model for predicting human hepatic, metabolic clearance from in vitro intrinsic clearance data in hepatocytes and microsomes. Drug Metab. Dispos. 33(9):1304–1311 (2005). doi: 10.1124/dmd.105.004259.PubMedCrossRefGoogle Scholar
  5. 5.
    H. C. Rawden et al. Microsomal prediction of in vivo clearance and associated interindividual variability of six benzodiazepines in humans. Xenobiotica. 35(6):603–625 (2005). doi: 10.1080/00498250500162870.PubMedCrossRefGoogle Scholar
  6. 6.
    R. S. Obach. Prediction of human clearance of twenty-nine drugs from hepatic microsomal intrinsic clearance data: An examination of in vitro half-life approach and nonspecific binding to microsomes. Drug Metab. Dispos. 27(11):1350–1359 (1999).PubMedGoogle Scholar
  7. 7.
    H. S. Brown, M. Griffin, and J. B. Houston. Evaluation of cryopreserved human hepatocytes as an alternative in vitro system to microsomes for the prediction of metabolic clearance. Drug Metab. Dispos. 35(2):293–301 (2007). doi: 10.1124/dmd.106.011569.PubMedCrossRefGoogle Scholar
  8. 8.
    A. Rostami-Hodjegan, and G. T. Tucker. Simulation and prediction of in vivo drug metabolism in human populations from in vitro data. Nat. Rev. Drug Discov. 6(2):140–148 (2007). doi: 10.1038/nrd2173.PubMedCrossRefGoogle Scholar
  9. 9.
    M. Mistry, and J. B. Houston. Glucuronidation in vitro and in vivo. Comparison of intestinal and hepatic conjugation of morphine, naloxone, and buprenorphine. Drug Metab. Dispos. 15(5):710–717 (1987).PubMedGoogle Scholar
  10. 10.
    M. G. Soars, B. Burchell, and R. J. Riley. In vitro analysis of human drug glucuronidation and prediction of in vivo metabolic clearance. J. Pharmacol. Exp. Ther. 301(1):382–390 (2002). doi: 10.1124/jpet.301.1.382.PubMedCrossRefGoogle Scholar
  11. 11.
    S. Boase, and J. O. Miners. In vitroin vivo correlations for drugs eliminated by glucuronidation: investigations with the model substrate zidovudine. Br. J. Clin. Pharmacol. 54(5):493–503 (2002). doi: 10.1046/j.1365-2125.2002.01669.x.PubMedCrossRefGoogle Scholar
  12. 12.
    J. J. Engtrakul et al. Altered AZT (3′-azido-3′-deoxythymidine) glucuronidation kinetics in liver microsomes as an explanation for underprediction of in vivo clearance: comparison to hepatocytes and effect of incubation environment. Drug Metab. Dispos. 33(11):1621–1627 (2005). doi: 10.1124/dmd.105.005058.PubMedCrossRefGoogle Scholar
  13. 13.
    M. B. Fisher et al. In vitro glucuronidation using human liver microsomes and the pore-forming peptide alamethicin. Drug Metab. Dispos. 28(5):560–566 (2000).PubMedGoogle Scholar
  14. 14.
    M. G. Soars, B. J. Ring, and S. A. Wrighton. The effect of incubation conditions on the enzyme kinetics of udp-glucuronosyltransferases. Drug Metab. Dispos. 31(6):762–767 (2003). doi: 10.1124/dmd.31.6.762.PubMedCrossRefGoogle Scholar
  15. 15.
    M. B. Fisher et al. The role of hepatic and extrahepatic UDP-glucuronosyltransferases in human drug metabolism. Drug Metab. Rev. 33(3–4):273–297 (2001). doi: 10.1081/DMR-120000653.PubMedCrossRefGoogle Scholar
  16. 16.
    J. K. Ritter. Intestinal UGTs as potential modifiers of pharmacokinetics and biological responses to drugs and xenobiotics. Expert. Opin. Drug Metab. Toxicol. 3(1):93–107 (2007). doi: 10.1517/17425255.3.1.93.PubMedCrossRefGoogle Scholar
  17. 17.
    M. F. Paine et al. The human intestinal cytochrome P450 “pie”. Drug Metab. Dispos. 34(5):880–886 (2006). doi: 10.1124/dmd.105.008672.PubMedCrossRefGoogle Scholar
  18. 18.
    A. Galetin, and J. B. Houston. Intestinal and hepatic metabolic activity of five cytochrome P450 enzymes—impact on prediction of first-pass metabolism. J. Pharmacol. Exp. Ther. 318(3):1220–1229 (2006). doi: 10.1124/jpet.106.106013.PubMedCrossRefGoogle Scholar
  19. 19.
    R. H. Tukey, and C. P. Strassburg. Genetic multiplicity of the human UDP-glucuronosyltransferases and regulation in the gastrointestinal tract. Mol. Pharmacol. 59(3):405–414 (2001).PubMedGoogle Scholar
  20. 20.
    J. H. Lin, M. Chiba, and T. A. Baillie. Is the role of the small intestine in first-pass metabolism overemphasized? Pharmacol. Rev. 51(2):135–158 (1999).PubMedGoogle Scholar
  21. 21.
    X. Cao et al. Why is it challenging to predict intestinal drug absorption and oral bioavailability in human using rat model. Pharm. Res. 23(8):1675–1686 (2006). doi: 10.1007/s11095-006-9041-2.PubMedCrossRefGoogle Scholar
  22. 22.
    O. Bernard, and C. Guillemette. The main role of UGT1A9 in the hepatic metabolism of mycophenolic acid and the effects of naturally occurring variants. Drug Metab. Dispos. 32(8):775–778 (2004). doi: 10.1124/dmd.32.8.775.PubMedCrossRefGoogle Scholar
  23. 23.
    K. Bowalgaha, and J. O. Miners. The glucuronidation of mycophenolic acid by human liver, kidney and jejunum microsomes. Br. J. Clin. Pharmacol. 52(5):605–609 (2001). doi: 10.1046/j.0306-5251.2001.01487.x.PubMedCrossRefGoogle Scholar
  24. 24.
    E. J. Jeong et al. Species- and disposition model-dependent metabolism of raloxifene in gut and liver: role of UGT1A10. Drug Metab. Dispos. 33(6):785–794 (2005). doi: 10.1124/dmd.104.001883.PubMedCrossRefGoogle Scholar
  25. 25.
    D. C. Kemp, P. W. Fan, and J. C. Stevens. Characterization of raloxifene glucuronidation in vitro: contribution of intestinal metabolism to presystemic clearance. Drug Metab. Dispos. 30(6):694–700 (2002). doi: 10.1124/dmd.30.6.694.PubMedCrossRefGoogle Scholar
  26. 26.
    Y. Watanabe, M. Nakajima, and T. Yokoi. Troglitazone glucuronidation in human liver and intestine microsomes: high catalytic activity of UGT1A8 and UGT1A10. Drug Metab. Dispos. 30(12):1462–1469 (2002). doi: 10.1124/dmd.30.12.1462.PubMedCrossRefGoogle Scholar
  27. 27.
    E. J. Jeong, H. Lin, and M. Hu. Disposition mechanisms of raloxifene in the human intestinal Caco-2 model. J. Pharmacol. Exp. Ther. 310(1):376–385 (2004). doi: 10.1124/jpet.103.063925.PubMedCrossRefGoogle Scholar
  28. 28.
    M. Gertz et al. Drug lipophilicity and microsomal protein concentration as determinants in the prediction of the fraction unbound in microsomal incubations. Drug Metab. Dispos. 36(3):535–542 (2008). doi: 10.1124/dmd.107.018713.PubMedCrossRefGoogle Scholar
  29. 29.
    D. Hallifax, and J. B. Houston. Binding of drugs to hepatic microsomes: comment and assessment of current prediction methodology with recommendation for improvement. Drug Metab. Dispos. 34(4):724–726 (2006). author reply 727, doi: 10.1124/dmd.105.007658.PubMedCrossRefGoogle Scholar
  30. 30.
    M. F. Paine et al. Characterization of interintestinal and intraintestinal variations in human CYP3A-dependent metabolism. J. Pharmacol. Exp. Ther. 283(3):1552–1562 (1997).PubMedGoogle Scholar
  31. 31.
    Z. E. Barter et al. Scaling factors for the extrapolation of in vivo metabolic drug clearance from in vitro data: reaching a consensus on values of human microsomal protein and hepatocellularity per gram of liver. Curr. Drug Metab. 8(1):33–45 (2007). doi: 10.2174/138920007779315053.PubMedCrossRefGoogle Scholar
  32. 32.
    K. Ito, and J. B. Houston. Prediction of human drug clearance from in vitro and preclinical data using physiologically based and empirical approaches. Pharm. Res. 22(1):103–112 (2005). doi: 10.1007/s11095-004-9015-1.PubMedCrossRefGoogle Scholar
  33. 33.
    K. R. Yeo, A. Rostami-Hodjegan, and G. T. Tucker. Abundance of cytochrome P450 in human liver: a meta-analysis. Br. J. Clin. Pharmacol. 57:687–688 (2004).Google Scholar
  34. 34.
    H. S. Brown et al. Prediction of in vivo drug–drug interactions from in vitro data: impact of incorporating parallel pathways of drug elimination and inhibitor absorption rate constant. Br. J. Clin. Pharmacol. 60(5):508–518 (2005). doi: 10.1111/j.1365-2125.2005.02483.x.PubMedCrossRefGoogle Scholar
  35. 35.
    A. G. Staines, M. W. Coughtrie, and B. Burchell. N-glucuronidation of carbamazepine in human tissues is mediated by UGT2B7. J. Pharmacol. Exp. Ther. 311(3):1131–1137 (2004). doi: 10.1124/jpet.104.073114.PubMedCrossRefGoogle Scholar
  36. 36.
    P. J. Kilford et al. Prediction of drug clearance by glucuronidation from in vitro data: Use of combined P450 and UGT cofactors in alamethicin activated human liver microsomes. Drug Metab. Dispos. 37(1):82–89 (2009).PubMedCrossRefGoogle Scholar
  37. 37.
    A. Rowland et al. Binding of inhibitory fatty acids is responsible for the enhancement of UDP-glucuronosyltransferase 2B7 activity by albumin: implications for in vitro–in vivo extrapolation. J. Pharmacol. Exp. Ther. 321(1):137–147 (2007). doi: 10.1124/jpet.106.118216.PubMedCrossRefGoogle Scholar
  38. 38.
    A. Rowland et al. The “albumin effect” and drug glucuronidation: bovine serum albumin and fatty acid-free human serum albumin enhance the glucuronidation of UDP-glucuronosyltransferase (UGT) 1A9 substrates but not UGT1A1 and UGT1A6 activities. Drug Metab. Dispos. 36(6):1056–1062 (2008). doi: 10.1124/dmd.108.021105.PubMedCrossRefGoogle Scholar
  39. 39.
    B. C. Sallustio, B. A. Fairchild, and P. R. Pannall. Interaction of human serum albumin with the electrophilic metabolite 1-O-gemfibrozil-beta-D-glucuronide. Drug Metab. Dispos. 25(1):55–60 (1997).PubMedGoogle Scholar
  40. 40.
    H. Spahn-Langguth, and L. Z. Benet. Acyl glucuronides revisited: is the glucuronidation process a toxification as well as a detoxification mechanism? Drug Metab. Rev. 24(1):5–47 (1992). doi: 10.3109/03602539208996289.PubMedCrossRefGoogle Scholar
  41. 41.
    K. A. Youdim. Application of CYP3A4 in vitro data to predict clinical drug–drug interactions; predictions of compounds as objects of interaction. Br. J. Clin. Pharmacol. 65(5):680–692 (2008).PubMedCrossRefGoogle Scholar
  42. 42.
    H. M. Jones, and J. B. Houston. Substrate depletion approach for determining in vitro metabolic clearance: time dependencies in hepatocyte and microsomal incubations. Drug Metab. Dispos. 32(9):973–982 (2004). doi: 10.1124/dmd.104.000125.PubMedCrossRefGoogle Scholar
  43. 43.
    Y. Mano, T. Usui, and H. Kamimura. The UDP-glucuronosyltransferase 2B7 isozyme is responsible for gemfibrozil glucuronidation in the human liver. Drug Metab. Dispos. 35(11):2040–2044 (2007). doi: 10.1124/dmd.107.017269.PubMedCrossRefGoogle Scholar
  44. 44.
    T. K. Kiang, M. H. Ensom, and T. K. Chang. UDP-glucuronosyltransferases and clinical drug–drug interactions. Pharmacol. Ther. 106(1):97–132 (2005). doi: 10.1016/j.pharmthera.2004.10.013.PubMedCrossRefGoogle Scholar
  45. 45.
    Y. K. Chen et al. Quantitative regioselectivity of glucuronidation of quercetin by recombinant UDP-glucuronosyltransferases 1A9 and 1A3 using enzymatic kinetic parameters. Xenobiotica. 35(10–11):943–954 (2005). doi: 10.1080/00498250500372172.PubMedCrossRefGoogle Scholar
  46. 46.
    R. S. Obach, F. Lombardo, and N. J. Waters. Trend analysis of a database of intravenous pharmacokinetic parameters in humans for 670 drug compounds. Drug Metab. Dispos. 36(7):1385–1405 (2008).PubMedCrossRefGoogle Scholar
  47. 47.
    R. J. Bertz, and G. R. Granneman. Use of in vitro and in vivo data to estimate the likelihood of metabolic pharmacokinetic interactions. Clin. Pharmacokinet. 32(3):210–258 (1997).PubMedCrossRefGoogle Scholar
  48. 48.
    J. V. Willis et al. The pharmacokinetics of diclofenac sodium following intravenous and oral administration. Eur. J. Clin. Pharmacol. 16(6):405–410 (1979). doi: 10.1007/BF00568201.PubMedCrossRefGoogle Scholar
  49. 49.
    K. E. Thummel, D. D. Shen, N. Isoherranen, and H. E. Smith. Goodman & Gilman’s the pharmacological basis of therapeutics. 11th Edition. In L.L. Brunton (ed.), Section XV—Toxicology. Appendix II. Design and Optimization of Dosage Regimens: Pharmacokinetic Data. 11th ed. McGraw-Hill Medical Division, New York, 2006.Google Scholar
  50. 50.
    M. B. Rouini, M. Baluchestani, and L. Hakemi. Study of dose-linearity of gemfibrozil pharmacokinetics in human. Int. J. Pharmacol. 2(1):75–78 (2006).CrossRefGoogle Scholar
  51. 51.
    R. Bullingham et al. Pharmacokinetics and bioavailability of mycophenolate mofetil in healthy subjects after single-dose oral and intravenous administration. J. Clin. Pharmacol. 36(4):315–324 (1996).PubMedGoogle Scholar
  52. 52.
    K. K. Miles et al. An investigation of human and rat liver microsomal mycophenolic acid glucuronidation: evidence for a principal role of UGT1A enzymes and species differences in UGT1A specificity. Drug Metab. Dispos. 33(10):1513–1520 (2005). doi: 10.1124/dmd.105.004663.PubMedCrossRefGoogle Scholar
  53. 53.
    Y. J. Moon et al. Quercetin pharmacokinetics in humans. Biopharm. Drug Dispos. 29(4):205–217 (2008). doi: 10.1002/bdd.605.PubMedCrossRefGoogle Scholar
  54. 54.
    D. Hochner-Celnikier. Pharmacokinetics of raloxifene and its clinical application. Eur. J. Obstet. Gynecol. 85:23–29 (1999). doi: 10.1016/S0301-2115(98)00278-4.CrossRefGoogle Scholar
  55. 55.
    E. Rey et al. Pharmacokinetics of intravenous salbutamol in renal insufficiency and its biological effects. Eur. J. Clin. Pharmacol. 37(4):387–389 (1989). doi: 10.1007/BF00558505.PubMedCrossRefGoogle Scholar
  56. 56.
    D. A. Goldstein, Y. K. Tan, and S. J. Soldin. Pharmacokinetics and absolute bioavailability of salbutamol in healthy adult volunteers. Eur. J. Clin. Pharmacol. 32(6):631–634 (1987). doi: 10.1007/BF02456001.PubMedCrossRefGoogle Scholar
  57. 57.
    D. J. Morgan et al. Pharmacokinetics of intravenous and oral salbutamol and its sulphate conjugate. Br. J. Clin. Pharmacol. 22(5):587–593 (1986).PubMedGoogle Scholar
  58. 58.
    Y. Naritomi et al. Utility of hepatocytes in predicting drug metabolism: comparison of hepatic intrinsic clearance in rats and humans in vivo and in vitro. Drug Metab. Dispos. 31(5):580–588 (2003). doi: 10.1124/dmd.31.5.580.PubMedCrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media, LLC 2009

Authors and Affiliations

  • Helen E. Cubitt
    • 1
  • J. Brian Houston
    • 1
  • Aleksandra Galetin
    • 1
    Email author
  1. 1.School of Pharmacy and Pharmaceutical SciencesUniversity of ManchesterManchesterUK

Personalised recommendations