One Health Prescribing – New Analytical Methods to Inform Formulary Changes to Chiral Pharmaceuticals for Environmentally Friendlier Medicine

   Hydro Nation Scholars Programme

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  Dr Bruce Petrie, Dr Sharon Pfleger, Dr G Barron  No more applications being accepted  Competition Funded PhD Project (Students Worldwide)

About the Project

There is a need to reduce pollutants at source instead of relying on water treatment for their removal. The One Health Breakthrough Partnership ( is working to reduce pharmaceutical pollution entering the environment. This includes prescribing medicines that have less environmental impact based on environmental risk assessment (ERA). However, there is scope to improve this approach for chiral pharmaceuticals. Approximately 50% of all pharmaceuticals are chiral and exist as two or more forms known as enantiomers. Enantiomers of the same pharmaceutical differ in their 3-dimensional shape meaning they interact differently with biological systems. Different effects are observed on the human body and on non-target organisms in the environment (as well differences in their metabolism and biodegradation). Yet, the formulation of these medicines only considers the effects in the human body, and not the environment.

Commonly, chiral pharmaceuticals are formulated as the racemate which is an equal dose of both enantiomers. Pharmaceuticals can be formulated as individual enantiomers but is only done where there is a human need or benefit. For example, the common anti-inflammatory drug naproxen is produced as one enantiomer (S-naproxen) because the other enantiomer (R-naproxen) causes hepatic toxicity in humans. A One Health approach to pharmaceutical formulation whereby the human, animal and environmental effects of enantiomers is required. Enantiomers can have different toxicities in the environment but similar therapeutic effects in the human body. Therefore, prescribing the pharmaceutical as a single enantiomer formulation can reduce the environmental impact whilst having the same human therapeutic effect. Another issue with formulating pharmaceuticals as the racemate is that often only one enantiomer has the desired therapeutic effect in the human body. The other enantiomer is not needed but may still have a negative impact on non-target organisms in the environment.

Numerous pharmaceuticals which appear on Watch Lists or identified as a concern nationally are chiral. To identify where changes can be made to medicine formulations for a safer environment, there is a need to undertake ERA on pharmaceutical enantiomers. To date, ERA has focused on racemates and does not consider enantiomers individually. The therapeutic effect and excretion of pharmaceutical enantiomers in humans is well studied. However, only a few pharmaceuticals have any environmental toxicity and persistence data for enantiomers. This is due to a lack of analytical detection methods for environmental analysis of enantiomers. Existing (conventional) analytical methods do not enable the measurement of enantiomers as they have identical physical and chemical properties. The project will involve developing novel analytical methods which can separate, and measure enantiomers independently using enantioselective ultra-high performance liquid chromatography-tandem mass spectrometry. These methods will then be applied to establish a body of evidence on the fate and effects of enantiomers in the environment such that changes to medicine formulations for a safer environment can be implemented. 

Biological Sciences (4) Chemistry (6) Environmental Sciences (13)

Funding Notes

The Hydro Nation Scholars Programme is an open competition for PhD Scholars to undertake approved projects, hosted within Scottish Universities and Research Institutes. This project will be hosted by Robert Gordon University. Full funding is available from the Scottish Government (to host institutions via the Scottish Funding Council). The funding available will be in line with the UKRI doctoral stipend levels and indicative fees. Applicants should have a first-class honours degree in a relevant subject or a 2.1 honours degree plus Masters (or equivalent). Shortlisted candidates will be interviewed on 26th or 27th January 2023