Use of toxicity assays for enantiomeric discrimination of pharmaceutical substances.

Toxicity assays are commonly used as general indicators of environmental water pollution. In the study described here, selected toxicity tests have been used to evaluate the different toxicity levels of enantiomers of different pharmaceutical drugs that can be found as potential contaminants in water environments. Isomers of dopa, fluoxetine, and atenolol were tested with three aquatic organisms corresponding to different trophic levels: Daphnia magna (a crustacean), Pseudokirchneriella subcapitata (a microalga), and Tetrahymena thermophila (a protozoan). Different levels of toxicity were observed for each enantiomer, suggesting that significant enantioselectivity occurs in aquatic toxicity and that such enantiomeric differences must be considered when evaluating the ecological effects of these compounds.