Most pharmaceuticals are found at trace concentrations in aquatic systems, but their continuous release and potential accumulation can lead to adverse health effects in exposed organisms. Concentrations can vary temporally, driven by variations in discharges of receiving waters, sorption to sediments, and other biotic and abiotic exchange processes. The principal aim of this research was to better understand the occurrence, trends, and dynamics of pharmaceuticals in a cold-climate, riverine environment. To this end, a suite of seven representative antipsychotic pharmaceuticals was measured upstream and downstream of two wastewater treatment plants (WWTPs) in Saskatchewan, Canada, located in the South Saskatchewan River and Wascana Creek, respectively, across three seasons. Concentrations of analytes were in the ng/L range and generally greater downstream of both WWTPs compared to upstream. Some compounds, including the tricyclic antidepressant amitriptyline, which was the most abundant analyte in water and sediment from both sites and across seasons, reached low μg/L concentrations. Data collected from this research effort indicate contamination with antipsychotic pharmaceuticals, with the potential to adversely impact exposed organisms.

In vitro biotransformation assays with primary trout hepatocytes (RT-HEP) or liver subcellular fractions (RT-S9) have been proposed as valuable tools to help scientists and regulators better understand the toxicokinetics of chemicals. While both assays have been applied successfully to a diversity of neutral organic chemicals, only the RT-S9 assay has been applied to a large number of ionizable organic chemicals. Here, a combination of an in vitro biotransformation assay with RT-HEP with an active transport assay based on the permanent rainbow trout liver cell line RTL-W1 was used to qualitatively predict the potential hepatic clearance of nine psychotropic drugs with various degrees of ionization. Predictions were compared with rates of clearance measured in isolated perfused rainbow trout livers, and the importance of active transport was verified in the presence of the active transport inhibitor cyclosporin A. For the first time, it was demonstrated that a combination of biotransformation and active transport assays is powerful for the prediction of rates of hepatic clearance of ionizable chemicals. Ultimately, it is expected that this approach will allow for use of fewer animals while at the same time improving our confidence in the use of data from in vitro assays in chemical risk assessment.