Photodegradation of Buspirone: Ecotoxicological Assessment and Identification of Photoproducts

Buspirone is an anxiolytic drug used for the treatment of generalized anxiety disorder. Even though it was patented 50 years ago, it is still among the top three most commonly prescribed anti-anxiety medications in the US. Its fate in the environment and ecotoxic effects have not yet been assessed. In this study, the direct and indirect (with humic acids) photodegradation of buspirone was assessed using the SunTest CPS+ sunlight simulator in two radiation ranges: 280-800 nm and 290-800 nm. The concentration of buspirone and the formation of photoproducts were assessed using liquid chromatography with a diode array and mass spectrometry detector. Toxicity was assessed using biotests with luminescent bacteria and protozoan Spirostomum ambiguum, as well as in silico analyses on daphnia, fish, and protozoan Tetrahymena pyriformis. Buspirone was degraded by sunlight. Expanding the radiation range from 290 to 280 nm accelerated degradation. Humic acids, however, had no effect in either case. The structures of 24 phototransformation products have been proposed. Neither buspirone nor most of its photodegradation products were toxic. Only two derivatives had a calculated 96h-LC₅₀ value for fish below 1 mg L^-1. The obtained results indicate a low environmental risk of buspirone.