The toxic effect of the antibiotic metronidazole on aquatic organisms.

The acute toxicity of metronidazole was tested on freshwater and marine organisms. The tests showed effect on Chlorella sp. and Selenastrum capricornutum. 72-hr EC10 of 2.03 mg/l and 19.9 mg/l respectively and 72-hr EC50 values of 12.5 mg/l and 40.4 mg/l respectively were among the results obtained. No acute lethal effect was observed on Acartia tonsa or Brachydanio rerio. The study demonstrates the potential ecotoxic effect of metronidazole, suggesting the need for further investigations of the environmental exposure of medicinal substances.