Intracerebral microdialysis coupled to LC-MS/MS for the determination tramadol and its major pharmacologically active metabolite O-desmethyltramadol in rat brain microdialysates.

Abstract

A rapid and sensitive method involving liquid chromatography electrospray tandem mass spectrometry (LC-ESI-MS/MS) coupled to an intracerebral microdialysis technique was developed for the determination and pharmacokinetic investigation of tramadol and its major active metabolite O-desmethyltramadol (ODT) in rat brain. The microdialysis samples were separated on a C18 column and eluted with a mobile phase of acetonitrile-water-formic acid (50:50:0.1; v/v/v) at a flow rate of 0.3mL/min. The ESI-MS/MS spectra were performed in electrospray positive ion mode, and the analytes were detected by multiple reaction monitoring (MRM) of the transitions m/z [M+H]+ 264.3→58.2 for tramadol, m/z [M+H]+ 250.3→58.3 for ODT, and m/z [M+H]+ 379.4→264.0 for ambroxol (internal standard; IS). The total run time was 4.0min. A lower limit of quantitation (LLOQ) was achieved as 1ng/mL for tramadol and 0.5ng/mL for ODT, with excellent linearity over a concentration range of 1~500ng/mL (r>0.99) for tramadol and 0.5~50ng/mL for ODT (r>0.99), respectively. The proposed method was successfully applied to the pharmacokinetic studies of tramadol and ODT in rat brain. Copyright © 2017 John Wiley & Sons, Ltd.