Updated

If you have asthma, your doctor might have you on heartburn drugs to ease your wheezing. But that's not necessarily a good idea, according to a fresh look at the medical evidence.

"Because these drugs are so common -- most of them are over-the-counter -- a lot of people are put on them," said Dr. Walter Chan, who worked on the new study. "We found the effect is so small it's almost insignificant."

Early findings had led many doctors to believe heartburn drugs such as Prilosec or Nexium would help take the edge off asthma attacks. The idea was that during reflux, small droplets of stomach fluid would get into the airways and exacerbate breathing problems.

But more recent studies have yielded mixed results. So Chan, of Brigham and Women's Hospital in Boston, and his colleagues decided to summarize all the best evidence on the treatment.

They found 11 gold-standard studies of heartburn drugs in asthma, including more than 2,500 adult patients, with or without heartburn.

When the results of all those studies were pooled, patients who took the drugs did show an increase in airway capacity as measured by an exhalation test, compared with those who took only a placebo. Yet the effect was so small -- about half of what would even be perceptible -- it didn't lead the participants to feel any better.

People with frequent heartburn experienced a somewhat bigger benefit, although it's unclear if it's big enough to make a real difference. What's more, those individuals suffering from both asthma and heartburn might already be taking the heartburn medications to keep their acid in check.

Heartburn, or gastroesophageal reflux disease (GERD), is the most common digestive complaint in the U.S., affecting about a third of the population, according to the researchers. Asthma affects about 7 percent of people in the U.S., and the two conditions often go hand in hand, with a significant portion of asthma sufferers also experiencing GERD.

A month's worth of heartburn drugs costs about $30 to $40, said Chan, whose findings appear in the Archives of Internal Medicine.

While the researchers didn't find any appreciable side effects in the studies they looked at, Chan told Reuters Health the drugs have been linked to a small increase in risk of pneumonia, stomach infections and bone thinning.

"We don't recommend the routine use of the drugs in asthma," he concluded, adding that his findings line up with previous results for children. "Patients who have routine reflux may achieve more benefit, but that needs to be studied further."