PT - JOURNAL ARTICLE AU - Paul Riska AU - Michael Lamson AU - Thomas MacGregor AU - John Sabo AU - Susan Hattox AU - Joseph Pav AU - James Keirns TI - Disposition and Biotransformation of the Antiretroviral Drug Nevirapine in Humans DP - 1999 Aug 01 TA - Drug Metabolism and Disposition PG - 895--901 VI - 27 IP - 8 4099 - http://dmd.aspetjournals.org/content/27/8/895.short 4100 - http://dmd.aspetjournals.org/content/27/8/895.full SO - Drug Metab Dispos1999 Aug 01; 27 AB - The pharmacokinetics and biotransformation of the antiretroviral agent nevirapine (NVP) after autoinduction were characterized in eight healthy male volunteers. Subjects received 200-mg NVP tablets once daily for 2 weeks, followed by 200 mg twice daily for 2 weeks. Then they received a single oral dose (solution) of 50 mg containing 100 μCi of [14C]NVP. Biological fluids were analyzed for total radioactivity, parent compound (HPLC/UV), and metabolites (electrospray liquid chromatography/mass spectroscopy and liquid chromatography/tandem mass spectroscopy). Mean recovery of radioactivity was 91.4%, with 81.3% excreted in urine and 10.1% recovered in the feces over a period of 10 days. Circulating radioactivity was evenly distributed between whole blood and plasma. At maximum plasma concentration, parent compound accounted for ∼75% of the circulating radioactivity. Mean plasma elimination half-lives for total radioactivity and NVP were 21.3 and 20.0 h, respectively. Several metabolites were identified in urine including 2-hydroxynevirapine glucuronide (18.6%), 3-hydroxynevirapine glucuronide (25.7%), 12-hydroxynevirapine glucuronide (23.7%), 8-hydroxynevirapine glucuronide (1.3%), 3-hydroxynevirapine (1.2%), 12-hydroxynevirapine (0.6%), and 4-carboxynevirapine (2.4%). Greater than 80% of the radioactivity in urine was made up of glucuronidated conjugates of hydroxylated metabolites of NVP. Thus, cytochrome P-450 metabolism, glucuronide conjugation, and urinary excretion of glucuronidated metabolites represent the primary route of NVP biotransformation and elimination in humans. Only a small fraction of the dose (2.7%) was excreted in urine as parent compound. The American Society for Pharmacology and Experimental Therapeutics