Metabolomics has achieved great progress over the last 20 years, and it is currently considered a mature research field. As a result, the number of applications in toxicology, biomarker, and drug discovery has also increased. Toxicometabolomics has emerged as a powerful strategy to provide complementary information to study molecular-level toxic effects, which can be combined with a wide range of toxicological assessments and models. The zebrafish model has gained importance in recent decades as a bridging tool between in vitro assays and mammalian in vivo studies in the field of toxicology. Furthermore, as this vertebrate model is a low-cost system and features highly conserved metabolic pathways found in humans and mammalian models, it is a promising tool for toxicometabolomics. This short review aims to introduce zebrafish researchers interested in understanding the effects of chemical exposure using metabolomics to the challenges and possibilities of the field, with a special focus on toxicometabolomics-based mass spectrometry. The overall goal is to provide insights into analytical strategies to generate and identify high-quality metabolomic experiments focusing on quality management systems (QMS) and the importance of data reporting and sharing.

The levels of cocaine (COC) and its metabolites benzoylecgonine (BE) and cocaethylene (COE) in wastewater samples from Brasilia, Brazil, were determined using liquid chromatography coupled to hybrid quadrupole-time-of-flight mass spectrometry. The former metabolite was used to estimate cocaine consumption using a country-tuned correction factor that considers BE excretion rates for different routes of administration as well as the fraction of crack users in Brazil. A day-to-day analysis during a week indicates higher cocaine use in weekends with peaks on Sunday in both southern (7385 ± 121 mg day⁻¹ 1000 inhab⁻¹) and northern (3566 ± 171 mg day⁻¹ 1000 inhab⁻¹) areas of Brasilia. A significant high cocaine use was also observed in the Carnival Day of 2018 (6229 ± 219 mg day⁻¹ 1000 inhab⁻¹). COE/BE ratios were used to assess COC and alcohol co-consumption since COE is produced during the co-consumption of both substances. Higher ratios were also observed during the weekend. However, higher ratios on Saturdays rather than Sundays may be explained by the decrease of BE excretion during the co-consumption with alcohol, which may lead to an underestimation of the cocaine use estimates on Saturdays, as well as by different patterns of co-consumption by powder and crack users, where the latter usually drink lower amounts of alcohol. Our data suggest that only 3% of cocaine was seized by the local Technical Police during the study.