Monitoring and toxicological evaluation of antihistaminic drugs in surface waters

A HPLC method for the simultaneous determination of three widely used antihistaminic drugs, diphenhydramine (DIP), oxatomide (OXA) and promethazine (PRO), in surface waters and a toxicological assay using the bioluminescent bacterium Vibrio fischeri were developed. The analytical procedure was extended to the by-products from PRO photodegradation. The method involved pre-concentration and clean-up by SPE and HPLC analysis with diode array detection. Validation of the method was performed on synthetic mixtures and surface water samples spiked with the drugs, showing mean recoveries ranging from 93 and 107%, with RSD below 5.5%. Limits of detection in surface waters, calculated on 1.0 L of sampled waters, were in the range 0.6 – 0.8 g/L. The Vibrio fischeri test demonstrated toxicity due to PRO at a concentration of just 3.94 g/mL while the other antihistamines showed no significant toxicity until to 50.0 g/mL. However, toxicity of drug mixtures was greater than the sum of the values from single component samples. The presence of the studied drugs was monitored in two rivers in Calabria (Italy), collected along a period of seven months. DIP and OXA were not detected in any samples. On the contrary, PRO was found in two samples taken in July at a concentration of 1.98 and 2.31 g/L, both significantly below the values causing toxicity.