Chronic Toxicity of Diphenhydramine Hydrochloride and Erythromycin Thiocyanate to Daphnia, Daphnia magna, in a Continuous Exposure Test System

Diphenhydramine hydrochloride (DH; Benadryl (TM), an over-the-counter antihistamine) and erythromycin thiocyanate (ET; a commonly used macrolide antibiotic) are pharmaceutical compounds whose chronic toxicity to Daphnia magna had not been characterized. Continuous exposure to DH concentrations about 5 times greater than the maximum reported environmental concentration of 0.023 mu g/L for 21 days or to ET concentrations about 40 times the maximum reported environmental concentration of 6 mu g/L for 21 days did not significantly impact D. magna survival and production. In this study the no observable effect concentration for DH was 0.12 mu g/L and for ET was 248 mu g/L.