title: Automated gas chromatography/tandem mass spectrometry assay for tebufelone and a 13C,(18)O-labeled analog in plasma: applicabilityto absolute bioavailability determination.
abstract: An automated capillary gas chromatography/tandem mass spectrometry (GC/MS/MS) assay for the simultaneous quantitation of tebufelone (TE) and 13C, (18)O-labeled TE (TE-CO) in plasma was developed. This method permits the use of stable isotope coadministration (TE and TE-CO dosed concurrently via peroral and intravenous routes, respectively) for the determination of TE absolute bioavailability. The selectivity of MS/MS conducted on a triple-quadrupole instrument allowed minimal sample preparation and rapid analysis. Electron ionization produced molecular ions (M+) for TE, TE-CO, and the 3-methyl-TE internal standard which were selected in Q1 to undergo collisionally activated dissociation in Q2. Quantitation was achieved through monitoring product ions at m/z 248, 251 and 248, respectively, in Q3. A 2-1000 ng per sample (40 pg to 20 ng injected) quantitation range provided access to an effective 1-5000 p.p.b. plasma concentration range (0.2-2 g samples) for both TE and TE-CO. The assay showed no bias and less than 8% relative standard deviation over the entire range. The method was used to determine plasma levels of TE and TE-CO in four dogs receiving 2.5:2.5 mg/kg TE:TE-CO, intravenously. The pharmacokinetics of both isotopomers proved to be identical, indicating no isotope effect and verifying the chemical stability of the (18)O-carbonyl label under these dosing conditions. In addition, the applicability of this analytical approach to the determination of TE peroral bioavailability was initially tested in dogs.
authors.affiliation: Procter & Gamble Pharmaceuticals, Miami Valley Laboratories, Cincinnati, OH 45239-8707.
authors.forename: R L
authors.initials: RL
authors.lastname: Dobson
authors.forename: G R
authors.initials: GR
authors.lastname: Kelm
authors.forename: D M
authors.initials: DM
authors.lastname: Neal
mesh_terms: D000480:Alkynes / Q000097:blood* / Q000493:pharmacokinetics; D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000097:blood* / Q000493:pharmacokinetics; D001322:Autoanalysis / Q000379:methods; D001682:Biological Availability; D002247:Carbon Isotopes; D004285:Dogs; D005260:Female; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods; D006801:Humans; D010103:Oxygen Isotopes; D010636:Phenols / Q000097:blood* / Q000493:pharmacokinetics
chemical_list: D000480:Alkynes; D000894:Anti-Inflammatory Agents, Non-Steroidal; D002247:Carbon Isotopes; D010103:Oxygen Isotopes; D010636:Phenols; C064268:tebufelone