Drug residue accumulation in fish can be predicted with increasing accuracy

A study conducted at the University of Helsinki proposes new initiatives for predicting the environmental effects of pharmaceuticals with the help of molecular interactions in fish.

According to recent global studies, pharmaceutical residues occur in the aquatic environment all over the world. Very little is known about the effects of individual pharmaceutical agents and, above all, their mixtures on aquatic organisms. Carrying out animal testing on all pharmaceutical substances to assess their environmental risks is not sustainable. 

Doctoral Researcher Tea Pihlaja examined the effect of pharmaceuticals on what are known as CYP enzymes in the fish liver. In humans, CYP enzymes plays a very important role in the elimination of foreign substances. The drug–drug interactions brought about by this mechanism are well known, and their role is investigated as part of drug development. According to Pihlaja, her study offers a new path to determining the mechanisms of drug accumulation in fish caused by drug residues in the environment.

In her study, Pihlaja demonstrates that the function of the CYP enzymes of fish, in this case rainbow trout, is broadly inhibited by pharmaceutical agents, and in a different manner from corresponding human enzymes. Compared to drug residue concentrations in waterways, the inhibition of CYP enzyme function requires fairly high concentrations in fish, but the risk of the phenomenon increases if a drug accumulates in the fish body or if fish are exposed to drug mixtures. Interactions between drugs and other chemicals can therefore occur even at low environmental concentrations. 

In addition, Pihlaja developed new in vitro research methods to reduce animal testing and promote sustainability. According to Pihlaja, her results can be utilised, for example, in computational modelling of the environmental effects of pharmaceuticals to eliminate the need for animal testing in assessing related risks and, potentially, to design new pharmaceutical agents.

Tea Pihlaja’s doctoral thesis Bioaccumulation of pharmaceutical residues in fish - In vitro evaluation of the impact of cytochrome P450 interactions was examined on 26 April 2024 at the University of Helsinki’s Faculty of Pharmacy. Her opponent was Professor emeritus Helmut Segner, University of Bern. Serving as custos at the public examination was Tiina Sikanen.