Genetic testing to predict how individuals will respond to common medicines should be implemented without delay to reduce the risk of side-effects and ensure that everyone is given the right drug at the right dose, experts have said.
About 6.5% of UK hospital admissions are caused by adverse drug reactions, while most prescription medicines only work on 30% to 50% of people. A significant part of this is due to genetics: almost 99% of people carry at least one genetic variation that affects their response to certain drugs, including commonly prescribed painkillers, heart disease drugs and antidepressants. By the age of 70, about 90% of people are taking at least one of these medications.
A new report, published by the British Pharmacological Society and the Royal College of Physicians, argues that many of these issues could be addressed through pharmacogenomic testing, which allows personalised prescribing according to people’s genes.
“The ultimate goal is to make pharmacogenomic prescribing a reality for everyone within the NHS, which will empower healthcare professionals to deliver better, more personalised care,” said Sir Munir Pirmohamed, a professor of pharmacology and therapeutics at the University of Liverpool, who chaired the report’s working party.
“The aim of pharmacogenomics is to make sure patients get the right drug, at the right dose, at the right time to be able to improve their outcomes, treat their symptoms, cure their disease and prevent side-effects.”
Some pharmacogenomic testing is already done within the NHS. For example, patients with breast or colon cancer may be tested to see whether they can safely be prescribed the chemotherapy drug 5-fluorouracil.
However, other common drugs, such as the painkiller codeine, are known to work better, or cause more side-effects in some patients than others, but doctors do not routinely test before prescribing them.
About 8% of the UK population lack the gene that allows codeine to work properly, meaning they will not get any pain relief from it. Another example is the antibiotic gentamicin: about one person in every 500 is genetically predisposed to develop hearing loss if they take it.
“The UK is a world leader in genomic medicine, and the implementation of a wider range of pharmacogenomic tests would further demonstrate UK leadership,” said Pirmohamed. “Today we are calling on government and the health service to ensure that patients across the UK are offered these tests where there is evidence to show their utility.”
Prof Sir Mark Caulfield, president-elect of the British Pharmacological Society, who contributed to the report, said: “This report provides the blueprint and identifies the resources and actions needed to ensure pharmacogenomics becomes usual care in the NHS over the next three years.”
He added that reactive testing to investigate why someone isn’t responding to their medication, or is experiencing side-effects, could be implemented as soon as next year, subject to NHS approval.
Further ahead, patients could be offered a once-in-a-lifetime blood or saliva test to predict their responses to multiple drugs and guide their future treatment. Such testing would cost about £100–£150 per person, but could result in long-term savings to the NHS.
Each year, adverse drug reactions cost the NHS an estimated £650m, but this figure could be as high as £2bn, Pirmohamed said. “Adverse drug reactions as a whole cost a lot to the NHS. Even if we can prevent 30% of those through implementing pharmacogenomics, we’ll be saving a lot of money.”