Crosssubstances

Crosssubstances is a term used in pharmacology and toxicology to describe substances that exhibit cross-target activity or cross-reactivity across multiple biological systems or detection methods. The concept encompasses two related ideas: cross-target activity, where a single chemical interacts with more than one biological target (such as receptors, enzymes, or transporters), and cross-reactivity in analytical assays, where a compound interferes with the detection of another substance due to structural similarity or shared assay components.

Mechanisms include structural mimicry that enables binding to multiple targets, metabolic pathways that generate several active metabolites, and interactions with transporters or immunoassay components that produce misleading results. These mechanisms underlie both therapeutic polypharmacology and analytical interference in laboratory and clinical settings.

Applications and implications: in drug discovery, cross-substance profiling helps map polypharmacology and potential side effects; in toxicology and pharmacovigilance, they inform risk assessment for multimodal exposures; in forensic science, immunoassay cross-reactivity can yield false positives. Research methods include receptor binding and functional assays, pharmacokinetic modeling, and cheminformatics to predict cross-target activity. See also polypharmacology, drug-drug interaction, cross-reactivity, and immunoassay interference.