Proton pump inhibitors (PPIs) reduce the amount of acid made by the stomach and are used to treat acid reflux and stomach ulcers.
A study published in the journal Gut identified an association between long-term use of the drug and a 2.4 times higher risk of developing stomach cancer.
PPIsare one of the most popularly prescribed drugs in Australia for conditions such as gastro-oesophageal reflux disease, peptic ulcer disease and functional dyspepsia, according the the Royal College of Australian GPs.
A link between PPIs and a higher stomach cancer risk has previously been identified by academics - but never in a study that first eliminates a bacteria suspected of fuelling the illness's development.
Research by the University of Hong Kong and University College London found that after the Helicobacter plyori was removed, the risk of developing the disease still rose in line with the dose and duration of PPI treatment.
Daily use of PPIs was associated with a risk of developing the illness that was more than four-times higher (4.55) than those who used it weekly.
Similarly, when the drug was used for more than a year, the risk of developing stomach cancer rose by five-fold, and as high as eight-fold after three or more years, the findings showed.
The study concluded no firm cause and effect could be drawn, but doctors should "exercise caution when prescribing long-term PPIs... even after successful eradication of H plyori".
Responding to the study, Stephen Evans, professor of pharmacoepidemiology at the London School of Hygiene and Tropical Medicine, said: "Many observational studies have found adverse effects associated with PPIs.
"The most plausible explanation for the totality of evidence on this is that those who are given PPIs, and especially those who continue on them long-term, tend to be sicker in a variety of ways than those for whom they are not prescribed."
