Four million UK patients could benefit annually from genetic testing before being prescribed common medicines such as antidepressants and painkillers, according to new research from the University of East Anglia.

Better selection of medicines based on a patient's genetic information could mean less side-effects and better treatment outcomes.

The research, published in British Journal of Clinical Pharmacologywas carried out in in collaboration with Boots UK and Leiden University, Netherlands. It found that in more than one in five occasions there was the potential for a doctor or pharmacist to take action under international pharmacogenetic guidelines.

Researchers analysed 2019 NHS dispensing data across the UK to see how many patients are started on new prescriptions each year that could be potentially optimised by genetic testing. If this screening was applied to all new prescriptions, an estimated one in 11 (9.1%) would lead to a change of drug or dose, affecting over five million dispensed items.

Depending on the results of individual pharmacogenetic tests, they might either get a higher or lower starting dose than normal or be more closely monitored during the early stages of treatment.

Genetic information could lead to better selection of medicines with reduced side effects

Pharmacogenomic testing services already working in the Netherlands show that specially-trained GPs and pharmacists can carry out pre-prescribing tests and use the results to give advice on safer and more effective prescribing, delivering better patient outcomes.

Essra Youssef, a research pharmacist at UEA's School of Pharmacy, said: "We know over 95 per cent of the population carry a genetic marker that predicts an atypical response to at least one medicine. Our study looked at nine of these genetic markers, affecting 56 medicines that are commonly dispensed by community pharmacies in the UK. The most common of these are weak opioids, antidepressants and proton-pump inhibitors, which are prescribed to reduce stomach acid.

"Better selection of medicines based on a patient's genetic information could mean less side-effects and better treatment outcomes. This not only benefits the patient but also the NHS, as patients may not need to return to their GP so often to change their medication.

"It could also reduce hospital visits related to side effects of medicines. The testing process is quite simple in most cases, with a cheek swab sample collected and DNA analysed for genes related to medicines. As the cost of this testing continues to drop, the technology is more likely to represent good value for the NHS."