Uptake and metabolism of pharmaceuticals in aquatic invertebrates

This thesis explored the uptake into the freshwater shrimp (Gammarus pulex) and the water boatman (Notonecta glauca) of key pharmaceuticals drawn from different therapeutic classes and covering a range of physico-chemical properties. For one compound, uptake was also assessed using the freshwater snail Planobarius corneus. In G. pulex, bioconcentration factors (BCFs) ranged from 4.6 – 185900 and increased in the order moclobemide < 5-fluoruracil < carbamazepine < diazepam < carvedilol < fluoxetine. In N. glauca BCFs ranged from 0.1 – 1.6 and increased in the order 5-fluorouracil < carbamazepine < moclobemide < diazepam < fluoxetine < carvedilol. For P. corneus, the BCF for carvedilol was 57.3.
The metabolism of the study pharmaceuticals in the shrimp was investigated. Diazepam was found to be metabolized by G. pulex and a metabolite was detected and tentatively identified as nordiazepam. For the other five study compounds no metabolites were observed and it was inferred that metabolism in G. pulex may not influence the BCF.
The influence of dietary uptake was explored in the test organisms with carvedilol and fluoxetine. It was found that uptake from water was the predominant route of exposure for G. pulex but the data for N. glauca was contrasting and the exposure from the food was predominant. In both organisms a combination of food and water exposure resulted in a higher uptake of the compounds. The differences in degree of uptake from water across the organisms may be due to differences in mode of respiration, behaviour and the pH of the test system. The differences in degree of uptake from food across the organisms may be due to differences in feeding strategies. The degree of uptake of pharmaceuticals within an organism was related to the hydrophobicity of the pharmaceuticals.