From pharmaceuticals to toxic threats: Unveiling the impact of furosemide and by-products on fish model.

Pharmaceutical pollutants and their transformation products pose emerging challenges to aquatic ecosystems. Among these, furosemide (FUR), a widely used diuretic, has gained attention due to the potential ecological risks of its degradation products, saluamine (SAL) and pyridinium (PYR). This study investigates the sub-lethal effects of SAL and PYR on zebrafish larvae (Danio rerio), focusing on oxidative stress, cardiac function, and behavioral responses at environmentally relevant concentrations. Our results reveal that both SAL and PYR induce significant reactive oxygen species (ROS) production, leading to oxidative stress dysfunction. Cardiovascular analyses show marked alterations in heart rate, while behavioral assays demonstrate impaired locomotion, even at low exposure levels concentrations consistent with those detected in natural water bodies. Importantly, these effects were observed at concentrations where FUR itself showed no significant impact, emphasizing the greater toxicity potential of its degradation products. These findings underscore the need to incorporate pharmaceutical transformation products into environmental risk assessments and regulatory frameworks, as they may exert greater ecological threats than their parent compounds. Future studies are required to better elucidate the long-term and multi-trophic impacts of these pollutants on aquatic ecosystems.