Abstract
Nevirapine (NVP), a non-nucleoside inhibitor of HIV-1 reverse transcriptase, is concomitantly administered to patients with a variety of medications. To assess the potential for its involvement in drug interactions, cytochrome P-450 (CYP) reaction phenotyping of NVP to its four oxidative metabolites, 2-, 3-, 8-, and 12-hydroxyNVP, was performed. The NVP metabolite formation rates by characterized human hepatic microsomes were best correlated with probe activities for either CYP3A4 (2- and 12-hydroxyNVP) or CYP2B6 (3-and 8-hydroxyNVP). In studies with cDNA-expressed human hepatic CYPs, 2- and 3-hydroxyNVP were exclusively formed by CYP3A and CYP2B6, respectively. Multiple cDNA-expressed CYPs produced 8- and 12-hydroxyNVP, although they were produced predominantly by CYP2D6 and CYP3A4, respectively. Antibody to CYP3A4 inhibited the rates of 2-, 8-, and 12-hydroxyNVP formation by human hepatic microsomes, whereas antibody to CYP2B6 inhibited the formation of 3- and 8-hydroxyNVP. Studies using the CYP3A4 inhibitors ketoconazole, troleandomycin, and erythromycin suggested a role for CYP3A4 in the formation of 2-, 8-, and 12-hydroxyNVP. These inhibitors were less effective or ineffective against the biotransformation of NVP to 3-hydroxyNVP. Quinidine very weakly inhibited only 8-hydroxyNVP formation. NVP itself was an inhibitor of only CYP3A4 at concentrations that were well above those of therapeutic relevance (Ki = 270 μM). Collectively, these data indicate that NVP is principally metabolized by CYP3A4 and CYP2B6 and that it has little potential to be involved in inhibitory drug interactions.
Footnotes
-
Send reprint requests to: David A. Erickson, M.Sc., Dept. of Drug Metabolism and Pharmacokinetics, R&D Center, Boehringer Ingelheim Pharmaceuticals, Inc., 175 Briar Ridge Rd., Ridgefield, CT 06877. E-mail: derickso{at}rdg.boehringer-ingelheim.com
-
↵1 Present address: Cedra Corp., 8609 Cross Park Dr., Austin, TX 78754.
- Abbreviations used are::
- NVP
- nevirapine
- CYP
- cytochrome P-450
- EFCOD
- 7-ethoxy-4-trifluoromethylcoumarin deethylase
- MND
- S-mephenytoin N-demethylase
- Received March 17, 1999.
- Accepted September 7, 1999.
- The American Society for Pharmacology and Experimental Therapeutics
DMD 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.
|