title: Metabolism of the analgesic drug ULTRAM (tramadol hydrochloride) in humans: API-MS and MS/MS characterization of metabolites.
abstract: 1. Metabolism of the analgesic agent tramadol hydrochloride has been investigated after a single oral administration of tramadol to three male volunteers (100 mg/subject), and a urine pool (4-12h) was obtained. 2. Unchanged tramadol and a total of 23 metabolites, consisting of 11 Phase I metabolites (M1-11) and 12 conjugates (seven glucuronides, five sulphates), were profiled, characterized and tentatively identified in urine on the basis of API ionspray-MS and MS/MS data. 3. Of the metabolites, five (M1-5) had been previously identified. 4. The metabolites were formed via the following six metabolic pathways: (1) O-demethylation, (2) N-demethylation, (3) cyclohexyl oxidation, (4) oxidative N-dealkylation, (5) dehydration and (6) conjugation. 5. Pathways 1-3 appear to be major routes, forming seven O-desmethyl/N-desmethyl and hydroxycyclohexyl metabolites. 6. Pathways 1-3 in conjunction with pathway 6 produced seven glucuronides along with five sulphates. 7. In addition, the in vitro metabolism of tramadol was conducted using a human liver microsomal fraction in the presence of an NADPH-generating system. Unchanged tramadol (82% of the sample) plus eight metabolites (M1, M2, M4-6, tramadol-N-oxide (M31), OH-cyclohexyl-M1 (M32) and dehydrated tramadol-N-oxide), were profiled and tentatively identified on the basis of MS and MS/MS data.
authors.affiliation: Division of Preclinical Development, The R. W. Johnson Pharmaceutical Research Institute, Spring House, PA 19477, USA.
authors.forename: W N
authors.initials: WN
authors.lastname: Wu
authors.forename: L A
authors.initials: LA
authors.lastname: McKown
authors.forename: S
authors.initials: S
authors.lastname: Liao
mesh_terms: D000284:Administration, Oral; D000293:Adolescent; D000328:Adult; D000701:Analgesics, Opioid / Q000008:administration & dosage / Q000737:chemistry / Q000378:metabolism*; D020719:Glucuronides / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D013058:Mass Spectrometry; D008862:Microsomes, Liver / Q000378:metabolism; D015394:Molecular Structure; D014147:Tramadol / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism*
chemical_list: D000701:Analgesics, Opioid; D020719:Glucuronides; D014147:Tramadol