Screening for detection of new antidepressants, neuroleptics, hypnotics, and their metabolites in urine by GC-MS developed using rat liver microsomes

A gas chromatography-mass spectrometry (GC-MS) procedure for the detection of new antidepressants, neuroleptics, hypnotics, and their metabolites in urine is presented. The metabolites were first identified in rat liver microsome preparations by GC-MS after isolation and derivatization. Using these GC-MS data, a GC-MS screening was developed for urine as part of the authors' modified systematic toxicologic analysis procedure. After acid hydrolysis of a 2.5-mL aliquot of urine, a further aliquot was added. The mixture was then liquid-liquid extracted at pH 8-9, acetylated, and GC separated. Using mass chromatography with the ions m/z 58, 100, 120, 182, 195, 235, 261, 276, 284. and 293, the presence of new antidepressants, neuroleptics, hypnotics, and their metabolites could be indicated. Positive peaks could be identified by library search using the reference mass spectra recorded during the microsome studies. The intake of therapeutic doses of the following drugs could be monitored in urine: dosulepin, mirtazapine, moclobemide, nefazodone, trazodone, venlafaxine, and zolpidem. Olanzapine and zotepine were detectable in human urine only under steady-state conditions, and low-dose zopiclone was detectable only in overdose. The detection limit was less than 100 ng/mL (signal-to-noise ratio = 3) for the parent drugs.