Nearly a quarter of people in a large US study had been prescribed a medicine that could interact with their genetic makeup, highlighting the potential of pharmacogenomic testing to improve prescribing decisions.
The analysis, led by researchers at the University of Pittsburgh and published in Science Translational Medicine, examined genetic and health record data from almost 100,000 participants in the US National Institutes of Health's All of Us Research Programme.
The researchers assessed 16 pharmacogenes, a group of genes that influence how people respond to medicines, including how drugs are processed by the body and whether patients may experience reduced effectiveness or an increased risk of side effects.
Every participant carried at least one genetic variant in the genes examined, with a median of nine variants per person. By comparing genetic information with medical records, the team found that 24.4 per cent had been prescribed at least one medicine known to interact with a variant they carried.
The study also identified more than 17,000 previously unreported genetic variants and mapped the frequency of known medication-related variants across different ancestry groups.
The findings are significant because earlier pharmacogenomic research has often included limited representation from different racial and ethnic backgrounds. This can leave gaps in understanding how genetic differences influence medicine responses across populations.
The research used the All of Us programme, which aims to collect health and genetic information from one million people in the US to improve understanding of how genes, lifestyle and environment affect health.
Which commonly prescribed medicines could be affected?
The medicines most frequently identified in the analysis included ondansetron, ibuprofen, omeprazole and pantoprazole; and atorvastatin.
The researchers said more than 300 medicines already include information on their product labels about interactions with genetic variants, where testing may help guide treatment decisions.
One example involves a chemotherapy medicine used to treat colon cancer, which can cause serious toxicity in up to eight per cent of patients carrying certain genetic variants. Patients are tested before treatment to identify those who may need an alternative medicine or a different dosage.
Another example is clopidogrel. Genetic differences can affect how effectively some patients activate the medicine, potentially influencing treatment decisions.
Senior author Philip E Empey, associate professor at the University of Pittsburgh School of Pharmacy and associate director for pharmacogenomics at the university's Institute for Precision Medicine, said genetics could be one of several factors influencing how patients respond to treatment.
"Many people have experience with taking a medication that is not working well for them or that has a side effect," he said.
He added that the findings demonstrated the potential value of precision medicine in prescribing, particularly when genetic information could help clinicians select a more suitable medicine or adjust a dose.
Could genetic testing become part of routine prescribing?
The researchers suggest that pharmacogenomic results could be made available through electronic health records, allowing clinicians to receive alerts when a prescribed medicine may interact with a patient's genetic profile.
Such alerts could prompt prescribers to consider an alternative treatment or adjust the dosage, rather than relying solely on standard prescribing approaches.
Empey said patients who have already undergone pharmacogenomic testing should share their results with pharmacists and prescribers so the information can be incorporated into their medical records.
He also suggested that panel tests, which screen for multiple common genetic variants at once, could be useful for patients taking several medicines or starting treatments known to be affected by genetic differences.
However, the wider adoption of genetic screening will depend on whether its clinical benefits justify the cost, with policymakers and health insurers having a role in assessing the case for broader implementation.
The study also adds to ongoing discussions about the role of pharmacists in personalised prescribing. The Royal College of Pharmacy (as the Royal Pharmaceutical Society) produced guidance to help prescribers apply pharmacogenomic information in clinical practice, while NICE has highlighted the potential role of pharmacies in providing access to CYP2C19 genotype testing to guide clopidogrel treatment following stroke or transient ischaemic attack.
The researchers stressed that the use of genetic information must be implemented responsibly. Carrying a variant does not mean that a patient will necessarily experience an adverse reaction, and prescribing decisions must take account of other clinical factors.
Empey said falling testing costs and growing genetic datasets were making precision medicine increasingly relevant to healthcare.
The findings strengthen the case for integrating genetic information into prescribing systems, but further work will be needed to establish how widespread testing can be delivered affordably and equitably.
