Imagine a future where your medication is tailored to you. No trial and error, fewer side effects – a pill that works faster and more effectively. You’re a smaller female? Take 50mg. From a south Asian background? This class of drug will speed you to a swifter recovery.

According to a new report, the availability of personalised medicine is a step closer. Experts hope that we may eventually see a once-in-a-lifetime £150 genetic blood or saliva test that will provide the key to our future medical treatment. A major result would be that older people have to take fewer pills, so avoiding the widespread unpleasantness of “polypharmacy” – taking one drug to counteract the ill effects of another.

This week’s study from the British Pharmacological Society and the Royal College of Physicians revealed that most prescription medications surprisingly only work on 30 to 50 per cent of people. Indeed 6.5 per cent of people react so badly to their drugs, that they end up in hospital. The reason? Our genes: almost 99 per cent of people carry at least one genetic variation that affects their response to drugs including painkillers, heart disease drugs, and antidepressants. Thanks to the Human Genome Project, which was launched in 1990 and was finally declared complete on Thursday, scientists can now identify, map and sequence all our genes.

Sir Munir Pirmohamed is a clinical pharmacologist, geneticist and NHS chair of pharmacogenetics at the University of Liverpool. “We all vary in our makeup, and this variation determines how we respond to drugs,” he says. “When you visit a doctor, they will have some knowledge of you: your age, your sex – but not that vital genetic information. We try to do the best with the right drug and the right dose, but having a two-month trial is not good for the doctor, nor the patient especially. Genetic testing will lead to much better, more personalised care.”

Sir Munir, who chaired the report’s working party, describes the new advances as “an evolution, not a revolution”. “We’ve had the technology to do this for some time, but now it’s become cheaper, and more rapid,” he says.

This procedure of tailoring drugs to a patient’s genetic profile is known medically as pharmacogenomics, and experts agree that it has the potential to make a huge difference in many areas of medicine.

Ravi Sharma is director of the Royal Pharmaceutical Society and a contributor to the report. “How people respond to drugs is often based on a cocktail of lifestyle factors including diet, environment, whether they are pregnant, for example,” he says. “The genetic component is small but significant. As people differ genetically in how they appear physically, there is part of their genome that reacts differently to how they metabolise or excrete medication. There are four types of people: poor metabolisers, intermediate, and ultra-rapid; Asian people also process some drugs differently.”

So far, the greatest success for tailored medicine has been in the treatment of cancer. “Hospitals now carry out automatic DPYD testing [DPYD is the name of the gene] to find out the appropriate level of chemotherapy they should be given,” says Sharma. “Before this genetic test, people were dosed blindly. Many suffered from toxicity or even died. Pharmacogenomics has absolutely reduced prescribed harm.” As of 2020, 40,000 DPYD tests were being done in the UK every year.

As well as saving lives, cutting down on adverse drug reactions could save millions for the NHS. Each year, such reactions cost the health service an estimated £650 million, possibly even as much as £2 billion. Saving such huge sums would allow them to be channelled elsewhere.

And now this genetic technology could help large numbers of people, on a wide variety of drugs: painkillers, for example. “Codeine is a painkiller that needs to be broken down into morphine to be absorbed,” says Sir Munir. “But 8 per cent of people lack that particular enzyme, meaning the drug won’t work. On the other hand, 2 per cent of the population produce a lot of that enzyme, meaning there is a higher chance they will overdose. With genetic testing, we would have this knowledge in advance.”