title: High-performance liquid chromatographic assay for the simultaneous determination of tramadol and its metabolites in microsomal fractions of human liver.
abstract: A high-performance liquid chromatographic assay for the quantitative determination of the opioid analgesic tramadol and its metabolites is described. A homologue of tramadol [1-(m-hydroxyphenyl)-2-(N-ethyl-N-methylaminomethyl)cycloheptane-1 -ol hydrochloride] is used as internal standard. The assay allows the determination of tramadol O- and N-demethylation activity in vitro in microsomal fractions of human liver. Tramadol and its in vitro generated Phase I metabolites are extracted by a one-step extraction procedure from microsomal incubation mixtures using methylene chloride. Extraction efficiencies of tramadol, O-demethyltramadol and mono-N-demethyltramadol were 70, 91 and 94% respectively. The isocratic high-performance liquid chromatographic system employs a C18 reversed-phase column. The mobile phase is a mixture of methanol, ammonium hydrogencarbonate solution and ammonium hydroxide solution. Sensitivity of the assay was 0.5, 0.2 and 0.2 microgram/ml for tramadol, O-demethyltramadol and mono-N-demethyltramadol, respectively. Within-run precision of the overall assay was 13, 3.1 and 7.6% for tramadol, O-demethyltramadol and mono-N-demethyltramadol, respectively. Accuracy of the assay was determined as mean differences of concentrations added and found in microsomal fractions. It was -2.4% for tramadol, -0.85% for O-demethyltramadol and 0.32% for mono-N-demethyltramadol.
authors.affiliation: Department of General Internal Medicine, University of Bonn, Germany.
authors.forename: W D
authors.initials: WD
authors.lastname: Paar
authors.forename: P
authors.initials: P
authors.lastname: Frankus
authors.forename: H J
authors.initials: HJ
authors.lastname: Dengler
mesh_terms: D000701:Analgesics, Opioid / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D006801:Humans; D008862:Microsomes, Liver / Q000378:metabolism*; D012015:Reference Standards; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013050:Spectrometry, Fluorescence; D014147:Tramadol / Q000378:metabolism*
chemical_list: D000701:Analgesics, Opioid; D014147:Tramadol