title: Gas chromatographic quantitation of methoxyphenamine and three of its metabolites in plasma.
abstract: Sensitive gas chromatographic procedures for the determination of methoxyphenamine and three of its metabolites in plasma have been developed. The metabolites were measured using an electron-capture detector. This simple procedure is based on the precipitation of protein from a 1-ml plasma sample with 10% trichloroacetic acid, followed by aqueous derivatization with pentafluorobenzoyl chloride at pH 9.2 and a single-step cyclohexane extraction. The lower limit of detection for the N-desmethyl, O-desmethyl and aromatic 5-hydroxy metabolites of methoxyphenamine were 1.6, 3.1 and 2.2 ng ml-1, respectively, with coefficients of variation less than 10%. The poor electron-capture response of fluorinated derivatives of methoxyphenamine necessitated the use of nitrogen-phosphorus detection. Extractive derivatization with pentafluorobenzoyl chloride, without the need for protein precipitation, enabled quantitation of methoxyphenamine down to 3.8 ng ml-1 from a 2-ml aliquot of plasma. In a pilot study involving healthy volunteers who received a single oral dose of methoxyphenamine hydrochloride plasma concentration could be followed in all three subjects for at least 24, 32, 12 and 4 h for methoxyphenamine and the O-desmethyl, 5-hydroxy and N-desmethyl metabolites, respectively.
mesh_terms: D000318:Adrenergic beta-Agonists / Q000097:blood*; D000661:Amphetamine / Q000097:blood; D000662:Amphetamines; D055598:Chemical Phenomena; D002621:Chemistry; D002849:Chromatography, Gas / Q000379:methods; D006801:Humans; D007700:Kinetics; D008297:Male; D008694:Methamphetamine / Q000031:analogs & derivatives* / Q000097:blood; D013696:Temperature
chemical_list: D000318:Adrenergic beta-Agonists; D000662:Amphetamines; C043935:N-desmethylmethoxyphenamine; D008694:Methamphetamine; C043936:O-desmethylmethoxyphenamine; C043934:5-hydroxymethoxyphenamine; D000661:Amphetamine; C005157:methoxyphenamine