Limited bioconcentration of water-associated pharmaceutical active compounds through short-term exposure in signal crayfish (Pacifastacus leniusculus)

Pharmaceutical active compounds (PhACs) increasingly appear as complex mixtures in aquatic ecosystems, yet their bioconcentration in non-target organisms is poorly understood. This study examined tissue-specific distribution of five PhACs – bicalutamide, amitriptyline, furosemide, daidzein and sertraline – in signal crayfish (Pacifastacus leniusculus) after 96-hour exposure and an equal depuration period. Crayfish were subjected to environmentally relevant and 10-fold elevated mixture concentrations. Water and tissues (haemolymph, hepatopancreas, muscle) were analysed using ultra-high performance liquid chromatography–tandem mass spectrometry. Despite verified water concentrations and stable conditions, none of the compounds were quantifiable in tissues, except trace sertraline near the detection limit in some controls. The lack of detectable residues indicates minimal bioconcentration, likely due to physicochemical properties (low log K_ow), rapid metabolism and efficient excretion. Results underscore the need for longer exposures and metabolite-focused studies to better assess environmental fate, tissue kinetics and potential risks of PhAC mixtures in freshwater invertebrates.