A multi-analyte LC-MS/MS method for the determination of 57 pharmaceuticals and illicit drugs in plasma, and its application to poisoning cases

The diagnostic methods in an emergency scenario must be simple, fast, and efficient to provide an effectiveness and efficient treatment, thus reducing the consequences of exposure. Considering the sample analysis, the protein precipitation combined with LC-MS/MS has been shown to be a good strategy for the simultaneous determination of compounds of toxicological interest, such as medicines and drugs of abuse. In this study, a rapid and simple multi-analyte method was developed and validated for the quantification of 57 pharmaceuticals and illicit drugs in plasma samples. Sample pre-treatment consists of protein precipitation of 50 µL of the sample with 240 µL of organic solvent mixture (MeOH:ACN, 3:1, v/v), centrifugation, and injection into the LC-MS/MS, with a chromatographic run time of 7 min. The method was validated considering lower limit of quantification (LLOQ), interferences, linearity, precision, accuracy, dilution integrity, carryover, and matrix effect. The LLOQs ranged from 5 to 20 ng/mL and all analytes were linear (r2>0.99) in the tested concentration ranges. The method proved to be precise and accurate, presenting QC concentrations for all analytes within acceptable limits by the guideline used (CV % ≤20 % and bias ± 20 %). The developed method was successfully applied in 470 plasma samples of real cases of poisoning. A total of 80 % of the samples were positive for at least one substance, with acetaminophen (32.1 %), diazepam (25.1 %), and lidocaine (18.9 %) being the most detected. The most prevalent exposure circumstance among the cases was suicide attempt. The most frequent age groups were young adults between 20 and 29 years old and children under 5 years old. The methodology developed proved to be efficient in the simultaneous determination of 57 substances of toxicological interest, contributing to a correct diagnosis and, consequently, to the most appropriate management and treatment of the intoxicated patient. Furthermore, it is possible to observe the most commonly involved toxic agents in the Rio Grande do Sul, southern Brazil, helping to trace a profile of the poisoning patient, important in toxicovigilance actions.