Analysis of eight OTC drug components in postmortem dried blood spot samples by liquid chromatography-tandem mass spectrometry.

Recently, abuse and fatal overdoses of over-the-counter (OTC) medications have become serious social and health issues worldwide. However, many drug components in OTC medications that are abused have different chemical structures from those assessed by commercially available rapid drug test kits. In this research, we focused on using dried blood spot (DBS) samples to develop a simple and accurate method for forensic toxicological analysis of drugs of interest in deaths by poisoning. We combined the DBS method with liquid chromatography coupled with electrospray ionization-tandem mass spectrometry to quantify eight OTC drug components (apronal, caffeine, chlorpheniramine, dextromethorphan, diphenhydramine, diprophylline, noscapine, and promethazine). The linearities of the calibration curves were good in the concentration range of 0.1-2.0 μg/mL. The method achieved repeatable and accurate quantification of the eight target drugs with intra- and inter-assay coefficients of variation of below 13.0% and 12.6%, respectively. Comparison with our general practice method showed good positive correlations at the quantifiable concentrations of all drugs. Furthermore, when applied to an actual case, it was possible to diagnose death by drug poisoning, confirming the usefulness of this method.