Environmental pharmaceutical and antibiotic mixtures: An exposomics-guided framework for mechanistic toxicology

Pharmaceuticals and antibiotics occur in the environment as complex, time-varying mixtures, but their toxicological interpretation remains limited by targeted chemical lists, parent-compound monitoring, and single-compound testing. This narrative review synthesizes representative peer-reviewed evidence and integrates established exposomics, HRMS, EDA, AEP, and AOP concepts into a framework for mechanistic interpretation of environmental pharmaceutical and antibiotic mixtures. This integration connects target, suspect, and non-target HRMS screening with internal exposure verification, effect-directed analysis, aggregate exposure pathways, and AOP-informed mechanistic prioritization. The synthesis focuses on peer-reviewed studies that illustrate chemical screening, internal and tissue-resolved exposure, bioactivity anchoring, antibiotic transformation products, antimicrobial-resistance-relevant endpoints, and AEP/AOP-based mechanistic interpretation. Internal and tissue-resolved exposure data are emphasized as important for identifying biologically plausible drivers, particularly for neuroactive pharmaceuticals with conserved molecular targets and antibiotics that act through microbial, microbiome, immune, and resistance-selection pathways. Effect-directed analysis and mode-of-action-relevant bioassays provide a bridge between feature-rich exposome datasets and bioactivity-informed mechanistic interpretation. For antibiotics, inclusion of transformation products and antimicrobial resistance-related endpoints is significant because parent-only workflows can underestimate both chemical burden and biological relevance. AOP-network mapping offers a structured method for prioritizing key events, convergence points, and follow-up assays while separating confirmed evidence from tentative HRMS annotations. Finally, we summarize practical reporting and study-design considerations covering exposure verification, annotation confidence, QA/QC, bioactivity anchoring, omics interpretation, and qualitative evidence evaluation. This integrated approach can improve reproducibility, comparability, and decision relevance in the mechanistic toxicology of environmental pharmaceutical and antibiotic mixtures.