Skip to main content
Advertisement

Main menu

  • Home
  • Articles
    • Current Issue
    • Fast Forward
    • Latest Articles
    • Special Sections
    • Archive
  • Information
    • Instructions to Authors
    • Submit a Manuscript
    • FAQs
    • For Subscribers
    • Terms & Conditions of Use
    • Permissions
  • Editorial Board
  • Alerts
    • Alerts
    • RSS Feeds
  • Virtual Issues
  • Feedback
  • Submit
  • Other Publications
    • Drug Metabolism and Disposition
    • Journal of Pharmacology and Experimental Therapeutics
    • Molecular Pharmacology
    • Pharmacological Reviews
    • Pharmacology Research & Perspectives
    • ASPET

User menu

  • My alerts
  • Log in
  • Log out
  • My Cart

Search

  • Advanced search
Journal of Pharmacology and Experimental Therapeutics
  • Other Publications
    • Drug Metabolism and Disposition
    • Journal of Pharmacology and Experimental Therapeutics
    • Molecular Pharmacology
    • Pharmacological Reviews
    • Pharmacology Research & Perspectives
    • ASPET
  • My alerts
  • Log in
  • Log out
  • My Cart
Journal of Pharmacology and Experimental Therapeutics

Advanced Search

  • Home
  • Articles
    • Current Issue
    • Fast Forward
    • Latest Articles
    • Special Sections
    • Archive
  • Information
    • Instructions to Authors
    • Submit a Manuscript
    • FAQs
    • For Subscribers
    • Terms & Conditions of Use
    • Permissions
  • Editorial Board
  • Alerts
    • Alerts
    • RSS Feeds
  • Virtual Issues
  • Feedback
  • Submit
  • Visit jpet on Facebook
  • Follow jpet on Twitter
  • Follow jpet on LinkedIn
Research ArticleABSORPTION, DISTRIBUTION, METABOLISM, AND EXCRETION

The Cytochrome P450 2B6 (CYP2B6) Is the Main Catalyst of Efavirenz Primary and Secondary Metabolism: Implication for HIV/AIDS Therapy and Utility of Efavirenz as a Substrate Marker of CYP2B6 Catalytic Activity

Bryan A. Ward, J. Christopher Gorski, David R. Jones, Stephen D. Hall, David A. Flockhart and Zeruesenay Desta
Journal of Pharmacology and Experimental Therapeutics July 2003, 306 (1) 287-300; DOI: https://doi.org/10.1124/jpet.103.049601
Bryan A. Ward
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
J. Christopher Gorski
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
David R. Jones
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
Stephen D. Hall
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
David A. Flockhart
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
Zeruesenay Desta
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
  • Article
  • Figures & Data
  • Info & Metrics
  • eLetters
  • PDF
Loading

Abstract

We used human liver microsomes (HLMs) and recombinant cytochromes P450 (P450s) to identify the routes of efavirenz metabolism and the P450s involved. In HLMs, efavirenz undergoes primary oxidative hydroxylation to 8-hydroxyefavirenz (major) and 7-hydroxyefavirenz (minor) and secondary metabolism to 8,14-dihydroxyefavirenz. The formation of 8-hydroxyefavirenz in two HLMs showed sigmoidal kinetics (average apparent Km, 20.2 μM; Vmax, 140 pmol/min/mg protein; and Hill coefficient, 1.5), whereas that of 7-hydroxyefavirenz formation was characterized by hyperbolic kinetics (Km, 40.1 μM and Vmax, 20.5 pmol/min/mg protein). In a panel of 10 P450s, CYP2B6 formed 8-hydroxyefavirenz and 8,14-dihydroxyefavirenz from efavirenz (10 μM) at the highest rate. The Km value for the formation of 8-hydroxyefavirenz in CYP2B6 derived from hyperbolic Eq. 12.4 μM) was close to that obtained in HLMs (Km, 20.2 μM). None of the P450s tested showed activity toward 7-hydroxylation of efavirenz. When 8-hydroxyefavirenz (2.5 μM) was used as a substrate, 8,14-dihydroxyefavirenz was formed by CYP2B6 at the highest rate, and its kinetics showed substrate inhibition (Ksi, ∼94 μM in HLMs and ∼234 μM in CYP2B6). In a panel of 11 HLMs, 8-hydroxyefavirenz and 8,14-dihydroxyefavirenz formation rates from efavirenz (10 μM) correlated significantly with the activity of CYP2B6 and CYP3A. N,N',N”-Triethylenethiophosphoramide (thioTEPA; 50 μM) inhibited the formation rates of 8-hydroxyefavirenz and 8,14-dihydroxyefavirenz from efavirenz (10 μM) by ≥60% in HLMs) and CYP2B6, with Ki values < 4 μM. In conclusion, CYP2B6 is the principal catalyst of efavirenz sequential hydroxylation. Efavirenz systemic exposure is likely to be subject to interindividual variability in CYP2B6 activity and to drug interactions involving this isoform. Efavirenz may be a valuable phenotyping tool to study the role of CYP2B6 in human drug metabolism.

Footnotes

  • The study was funded by the National Institute of General Medical Sciences Grants R01-GM56898-01 and T32 GM 56898.

  • DOI: 10.1124/jpet.103.049601.

  • ABBREVIATIONS: HIV, human immunodeficiency virus; AIDS, acquired immunodeficiency syndrome; CNS, central nervous system; P450, cytochrome P450; HLM, human liver microsome; HPLC, high-performance liquid chromatography; LC/MS, liquid chromatography/mass spectrometry; MIC, metabolite intermediate complex; Ksi, substrate inhibition constant.

    • Received January 27, 2003.
    • Accepted March 28, 2003.
  • The American Society for Pharmacology and Experimental Therapeutics
View Full Text

JPET articles become freely available 12 months after publication, and remain freely available for 5 years. 

Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page. 

 

  • Click here for information on institutional subscriptions.
  • Click here for information on individual ASPET membership.

 

Log in using your username and password

Forgot your user name or password?

Purchase access

You may purchase access to this article. This will require you to create an account if you don't already have one.
PreviousNext
Back to top

In this issue

Journal of Pharmacology and Experimental Therapeutics: 306 (1)
Journal of Pharmacology and Experimental Therapeutics
Vol. 306, Issue 1
1 Jul 2003
  • Table of Contents
  • About the Cover
  • Index by author
Download PDF
Article Alerts
Sign In to Email Alerts with your Email Address
Email Article

Thank you for sharing this Journal of Pharmacology and Experimental Therapeutics article.

NOTE: We request your email address only to inform the recipient that it was you who recommended this article, and that it is not junk mail. We do not retain these email addresses.

Enter multiple addresses on separate lines or separate them with commas.
The Cytochrome P450 2B6 (CYP2B6) Is the Main Catalyst of Efavirenz Primary and Secondary Metabolism: Implication for HIV/AIDS Therapy and Utility of Efavirenz as a Substrate Marker of CYP2B6 Catalytic Activity
(Your Name) has forwarded a page to you from Journal of Pharmacology and Experimental Therapeutics
(Your Name) thought you would be interested in this article in Journal of Pharmacology and Experimental Therapeutics.
CAPTCHA
This question is for testing whether or not you are a human visitor and to prevent automated spam submissions.
Citation Tools
Research ArticleABSORPTION, DISTRIBUTION, METABOLISM, AND EXCRETION

The Cytochrome P450 2B6 (CYP2B6) Is the Main Catalyst of Efavirenz Primary and Secondary Metabolism: Implication for HIV/AIDS Therapy and Utility of Efavirenz as a Substrate Marker of CYP2B6 Catalytic Activity

Bryan A. Ward, J. Christopher Gorski, David R. Jones, Stephen D. Hall, David A. Flockhart and Zeruesenay Desta
Journal of Pharmacology and Experimental Therapeutics July 1, 2003, 306 (1) 287-300; DOI: https://doi.org/10.1124/jpet.103.049601

Citation Manager Formats

  • BibTeX
  • Bookends
  • EasyBib
  • EndNote (tagged)
  • EndNote 8 (xml)
  • Medlars
  • Mendeley
  • Papers
  • RefWorks Tagged
  • Ref Manager
  • RIS
  • Zotero

Share
Research ArticleABSORPTION, DISTRIBUTION, METABOLISM, AND EXCRETION

The Cytochrome P450 2B6 (CYP2B6) Is the Main Catalyst of Efavirenz Primary and Secondary Metabolism: Implication for HIV/AIDS Therapy and Utility of Efavirenz as a Substrate Marker of CYP2B6 Catalytic Activity

Bryan A. Ward, J. Christopher Gorski, David R. Jones, Stephen D. Hall, David A. Flockhart and Zeruesenay Desta
Journal of Pharmacology and Experimental Therapeutics July 1, 2003, 306 (1) 287-300; DOI: https://doi.org/10.1124/jpet.103.049601
del.icio.us logo Digg logo Reddit logo Twitter logo Facebook logo Google logo Mendeley logo
  • Tweet Widget
  • Facebook Like
  • Google Plus One

Jump to section

  • Article
    • Abstract
    • Materials and Methods
    • Results
    • Discussion
    • Footnotes
    • References
  • Figures & Data
  • Info & Metrics
  • eLetters
  • PDF

Related Articles

Cited By...

More in this TOC Section

  • Transport Is Not Rate-Limiting in Morphine Glucuronidation in the Single-Pass Perfused Rat Liver Preparation
  • Enhanced Hepatic Uptake and Bioactivity of Type α1(I) Collagen Gene Promoter-Specific Triplex-Forming Oligonucleotides after Conjugation with Cholesterol
  • Characterization of P-glycoprotein Inhibition by Major Cannabinoids from Marijuana
Show more ABSORPTION, DISTRIBUTION, METABOLISM, AND EXCRETION

Similar Articles

Advertisement
  • Home
  • Alerts
Facebook   Twitter   LinkedIn   RSS

Navigate

  • Current Issue
  • Fast Forward by date
  • Fast Forward by section
  • Latest Articles
  • Archive
  • Search for Articles
  • Feedback
  • ASPET

More Information

  • About JPET
  • Editorial Board
  • Instructions to Authors
  • Submit a Manuscript
  • Customized Alerts
  • RSS Feeds
  • Subscriptions
  • Permissions
  • Terms & Conditions of Use

ASPET's Other Journals

  • Drug Metabolism and Disposition
  • Molecular Pharmacology
  • Pharmacological Reviews
  • Pharmacology Research & Perspectives
ISSN 1521-0103 (Online)

Copyright © 2022 by the American Society for Pharmacology and Experimental Therapeutics