title: Sensitive quantitation of reboxetine enantiomers in rat plasma and brain, using an optimised reverse phase chiral LC-MS/MS method.
abstract: A sensitive liquid chromatography-mass spectrometry (LC-MS) method has been developed for stereoselective determination of reboxetine in rat plasma and brain homogenate (LLOQ, 50 pg/ml). The method optimised ionisation efficiency with an electro-ionspray source, by adjusting the composite flow conditions (rate, pH, organic content) from column eluent and post-column organic modifier. LC conditions utilized a chiral AGP column (5 microm) with 12.5 mM ammonium carbonate buffer adjusted with formic acid (pH 6.7) and included a wash step (0.05% acetic acid in water) to maintain assay robustness and chromatographic performance. The total method cycle time was 23 min. Imprecision (R.S.D.) was below 10% and inaccuracy (% error) below 7% for both enantiomers in plasma and brain homogenate, over a 2000-fold dynamic range (0.05-100 ng/ml). An automated liquid-liquid extraction technique was used (borate buffer, pH 10/tert-butyl methyl ether) and the matrix type used produced no difference in the assay performance. The method was successfully applied to determine the pharmacokinetic profiles of S,S- and R,R-reboxetine in rats, following subcutaneous administration of racemate drug.
authors.affiliation: Discovery Bioanalytical Group, Department of Pharmacokinetics, Dynamics and Metabolism, Pfizer Global Research and Development, Sandwich, Kent CT13 9NJ, UK. paul.turnpenny@pfizer.com
authors.forename: Paul
authors.initials: P
authors.lastname: Turnpenny
authors.forename: Daniela
authors.initials: D
authors.lastname: Fraier
mesh_terms: D018759:Adrenergic Uptake Inhibitors / Q000097:blood* / Q000737:chemistry / Q000493:pharmacokinetics; D000818:Animals; D001923:Brain Chemistry; D002853:Chromatography, Liquid / Q000379:methods*; D004355:Drug Stability; D005615:Freezing; D006863:Hydrogen-Ion Concentration; D015394:Molecular Structure; D009025:Morpholines / Q000097:blood* / Q000737:chemistry / Q000493:pharmacokinetics; D011786:Quality Control; D051381:Rats; D000077593:Reboxetine; D012015:Reference Standards; D012680:Sensitivity and Specificity; D021241:Spectrometry, Mass, Electrospray Ionization; D013237:Stereoisomerism; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D018759:Adrenergic Uptake Inhibitors; D009025:Morpholines; D000077593:Reboxetine