Proton pump inhibitors (PPIs) are drugs used to treat acid reflux. A recent report in Gut has linked long-term use of the drug to a more than doubled risk of developing stomach cancer.

Previous studies into the safety of PPIs had not first eliminated the effect of a bacteria known as Helicobacter pylori, which has been suspected of fuelling the illness’s development.

The latest research, carried out by the University of Hong Kong, compared the use of PPI against an alternative drug which limits acid production known as H2 blockers. The participants underwent ‘triple therapy’, which combines PPI and antibiotics to kill off the Helicobacter pylori bacteria. While H2 blockers were found to have no link to a higher risk of stomach cancer, PPIs were connected to an increased risk of more than double.

The study also showed that daily use of PPIs was associated with a risk of developing the illness that was more than four times higher than those who used it weekly, and when the drug was used for more than a year, the risk of developing stomach cancer rose five-fold, and as high as eight-fold after three or more years.

The study concluded that no firm cause and effect could be drawn, but that medical staff should "exercise caution when prescribing long-term PPIs".

Michelle Victor, solicitor in Leigh Day’s specialist product safety department, said:

“Previous research had looked at the link between PPIs and adverse and serious side effects, but this was undermined by being unable to factor in the effect of Helicobacter pylori bacteria.

“These new findings suggest that there could be substantial risks associated with the regular and prolonged use of proton pump inhibitors, especially when compared to comparative treatments available.

“We encourage the regulators and various manufacturers of PPIs to consider whether advice about the use of PPIs should be altered in light of this new research.”