Blood-thinner to treat heart disease proves ineffective for many South Asian patients due to a mutation in their DNA

A commonly prescribed blood-thinner may be ineffective for people of South Asian descent, a study suggests.

More than half of those with Bangladeshi and Pakistani ancestry have a genetic mutation that stops the drug, clopidogrel, from working properly.

Clopidogrel, also known as Plavix, is taken by millions of Britons to prevent heart attacks and strokes. It helps stop blood cells from sticking together, reducing the risk of a deadly clot.

Doctors have long known that many people do not respond to the medicine, but recent studies have found this is due to a genetic mutation in a gene called CYP2C19, which is responsible for making an enzyme that helps the liver activate the drug.

Previous research involving European populations have estimated that this is the case for around a third of people.

More than half of those with Bangladeshi and Pakistani ancestry have a genetic mutation that stops the drug, clopidogrel, from working properly

Clopidogrel, also known as Plavix, is taken by millions of Britons to prevent heart attacks and strokes

But the new study, by researchers at Queen Mary University of London, analysed the DNA of more than 40,000 British South Asians and concluded that, in this population, the prevalence is far higher.

They found that 57 per cent of those studied had the common genetic change that makes clopidogrel ineffective. Worryingly, two thirds of participants had been prescribed clopidogrel to prevent a secondary heart attack or stroke.

The researchers say that the high risk of recurrent heart attacks in Britons of Bangladeshi and Pakistani ancestry – more than three times that of people of European heritage – could be due to clopidogrel treatment failure.

Dr Emma Magavern, lead author of the research which was funded by the National Institute for Health and Care Research and Barts Charity, said: ‘It highlights the importance of using genetics to determine who can benefit from clopidogrel after a heart attack. 

‘Not doing so is likely to disproportionately disadvantage specific groups.’

She added that the findings further highlight the importance of including different groups in medical trials, saying that systematic under-representation of South Asians in studies has ‘obscured’ our understanding of the risk for this community.

There are many alternatives to clopidogrel available, including warfarin, aspirin and new types of blood thinners such as dabigatran.