Quantification of fluvoxamine, desmethyl fluvoxamine and fluvoxamine acid by LC-MS/MS in body fluids and solid...

Reports on the quantification of fluvoxamine (FLV) in human tissues have been quite limited, although FLV has been used as an antidepressant since 1986. Fluvoxamine acid (FLA) was shown to be the major metabolite of FLV in human urine in 1983, but its quantification is also limited to only three works using human plasma. The existence of desmethyl fluvoxamine (FLD) in human specimens was recently reported in 2025; therefore, its quantification has not yet been performed. Therefore, the present work deals with the quantifications of FLV, FLD and FLA in the human samples of blood, cerebrospinal fluid, pericardial fluid, bile, urine, liver, kidney and cerebrum obtained from a human cadaver; for the quantification, the standard addition method was employed using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The three top concentrations of FLV, FLD and FLA were observed in bile > liver > cerebrum, bile > liver > kidney and bile > kidney > urine, respectively. The three top relative ratios of FLD/FLA were observed in cerebrum > liver > bile, and the lowest ratio was observed in urine, and this may be one of the reasons why the previous work on FLV metabolites using urine in 1983 could not detect FLD. To our knowledge, this is the first report on the validated quantification of the new metabolite FLD by LC-MS/MS in the authentic human body fluids and solid tissues.