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Getting rid of bacteria linked to stomach ulcers may provide some relief for people with indigestion even if they don't have detectable ulcers, a new study suggests.

Indigestion, also called non-ulcer stomach pain, is a common complaint, but it is not clear exactly what causes it.

For people who aren't helped by lifestyle changes such as a modified diet, exercise and stress reduction, Brazilian researchers now suggests it may be worth trying a combination of heartburn drugs and antibiotics.

The idea is that wiping out the bug Helicobacter pylori would help soothe upset stomachs. So the researchers assigned 404 patients randomly to take either omeprazole, a heartburn drug, alone or with two antibiotics to kill the bacteria for ten days.

One year later, 49 percent of the patients taking the antibiotics said their symptoms had decreased by half, compared to 37 percent of those taking only the heartburn drug.

That means eight patients would have to take antibiotics for one to experience that kind of improvement, report Dr. Luiz Edmundo Mazzoleni of Hospital de Clinicas de Porto Alegre in Brazil and colleagues in the Archives of Internal Medicine.

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Non-ulcer stomach pain is estimated to account for up to five percent of primary-care visits in the U.S. and cost the nation at least $1 billion per year.

Earlier studies have come to mixed conclusions about the effect of wiping out Helicobacter pylori, which affects as many as half of the world's population, according to the researchers.

While their findings come from only one hospital, and so might not hold up elsewhere, they suggest testing for the bacteria and treating it in people with non-ulcer stomach pain. But they also call for more research into whether that strategy is cost-effective.

Like heartburn drugs, antibiotics come with side effects such as diarrhea and may also breed resistant bacteria.

In an editorial, Dr. Paul Moayyedi of McMaster University in Hamilton, Ontario, Canada, notes that there is now strong evidence that wiping out Helicobacter pylori can help a small group of patients.

"The challenge will be to establish the mechanism underlying this effect so that we can move forward and better treat our patients with this common and costly condition," he concludes.