Amoxicillin Doesn’t Help Some Respiratory Infections

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The next time you develop a lower respiratory tract infection, don't expect amoxicillin, the go-to antibiotic for these infections, to wipe it out.

According to a new study, amoxicillin isn’t any better than a placebo at treating the symptoms of a lower respiratory tract infection or preventing them from worsening. Amoxicillin is typically used to treat lower respiratory tract infections such as pneumonia and acute bronchitis.

British researchers treated 1,038 patients who had an acute lower respiratory tract infection with amoxicillin three times per day for seven days. A second group of 1,023 patients who also had a lower respiratory tract infection were treated with a placebo for the same period. The patients were age 18 or older and hailed from 12 European countries. All had had a cough for less than 28 days and were not suspected of having pneumonia.

Doctors assessed everyone's symptoms at the start of the study and study participants kept a daily diary, recording symptoms such as the severity of their cough, the presence of phlegm, shortness of breath, wheezing, a blocked or runny nose, chest pain, muscle aches, headaches, disturbed sleep and fever. They also rated each symptom, using a scale that ranged from "no problem" to "as bad as it could be."  Everyone also recorded non-respiratory tract symptoms such as diarrhea, skin rash and vomiting.

At the end of the week, the researchers found very little difference in the severity or duration of symptoms between the two groups. Even among people 60 and older, who were in otherwise good health, the antibiotics had minimal effect. Symptoms rated "moderately bad" or "worse" lasted a median of six days in the group that took the amoxicillin and seven days in the group that took the placebo.

More people who took the placebo had new or worsening symptoms compared to those who took amoxicillin — 19.3 percent versus 15.9 percent. But that difference was offset by the high number of people — 30 — who needed to be treated with amoxicillin to prevent one case of worsening symptoms. Just three people in the study were hospitalized — two who took antibiotics and one who took the placebo.

There was another intriguing finding. People who took amoxicillin had many more side effects than those who took the placebo. Nearly 29 percent of those who took amoxicillin reported side effects such as diarrhea, nausea and rash. By contrast, 14 percent of those in the placebo group experienced side effects.

"Our results show that most people get better on their own," researcher Paul Little, of the University of Southampton in the U.K., said in a statement. "Using amoxicillin to treat respiratory infections in patients not suspected of having pneumonia is not likely to help and could be harmful." What's more, overuse of amoxicillin can contribute to the development of antibiotic-resistant bacteria.

The researchers acknowledge that a small number of people would benefit from amoxicillin. They also can’t say whether or not the antibiotic would have helped older people who are seriously ill. The challenge, they wrote, is to "identify these individuals."

In general, they said, "Amoxicillin provides little symptomatic benefit for patients presenting in primary care who are judged to have clinically uncomplicated lower-respiratory-tract infections." Because of this, they added, "any mild, short-term benefits of antibiotic treatment should be balanced against the risks of side effects and, in the long-term, of fostering resistance."

The study appears online Dec. 19 in the journal The Lancet.

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