title: Intravenous kinetics and metabolism of [15,16-3H]naltrexonium methiodide in the rat.
abstract: After a 4 mg kg-1 bolus intravenous dose of [15,16-3H]naltrexonium methiodide to the rat, brain to plasma concentration ratios of the compound were 0.031 to 0.228 between 0.25 to 6 h after injection and the t 1/2 beta in plasma and brain were 2.92 and 7.61 h, respectively. Ethyl acetate-extracted radioactivity due to metabolites in plasma decayed with t 1/2 beta 1.83 h and the ratios of plasma concentration of metabolites to quaternary compound between 0.25 and 6 h were 0.014-0.026. Only unconjugated 7,8-dihydro-14-hydroxynormorphine, naltrexone and traces of 7,8-dihydro-14-hydroxynormorphinone were the metabolites in plasma. Naltrexone (but not normetabolites) was present only in traces in brain up to 0.5 h after injection and not at later times.
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism; D006207:Half-Life; D007700:Kinetics; D008297:Male; D009271:Naltrexone / Q000031:analogs & derivatives* / Q000097:blood*; D000644:Quaternary Ammonium Compounds; D051381:Rats; D011919:Rats, Inbred Strains; D013237:Stereoisomerism
chemical_list: D000644:Quaternary Ammonium Compounds; C032257:methylnaltrexone; D009271:Naltrexone