Specific and sensitive analysis of nefopam and its main metabolite desmethyl-nefopam in human plasma by liquid chromatography-ion trap tandem mass spectrometry.

A specific and sensitive liquid chromatography-tandem mass spectrometric (LC-MS-MS) method using an ion trap spectrometer was developed for quantitation of nefopam and desmethyl-nefopam in human plasma. Nefopam, desmethyl-nefopam and the internal standard (ethyl loflazepate) were extracted in a single step with diethyl ether from 1 mL of alkalinized plasma. The mobile phase consisted of acetonitrile with 0.