Why you should skip amoxicillin if you have bronchitis: It doesn’t work, study finds

By Deborah Kotz, Globe Staff

Despite abundant evidence showing that antibiotics don’t work against viral infections, many doctors still prescribe them -- especially amoxicillin -- for lower respiratory infections such as bronchitis, even after ruling out pneumonia. That’s because a few scant studies have indicated that it might help, at least a little bit, in shortening the severity or duration of symptoms.

That practice should change if medical practictioners follow the latest research published Wednesday in the journal Lancet. The European researchers randomly assigned amoxicillin or placebos to more than 2,000 patients diagnosed with bronchitis because of severe coughs, chest congestion, and other cold symptoms lingering for more than a week. They found that not only did antibiotics fail to alleviate or resolve symptoms faster than a placebo, but the drugs were more likely to lead to side effects including nausea, diarrhea, or rashes.

About 29 percent of patients treated with amoxicillin experienced these side effects compared with 24 percent of those in the placebo group. (Placebos have also been known to cause “side effects” if patients believe they are taking an active drug.)

“Neither duration of symptoms nor symptom severity was significantly affected by amoxicillin,” wrote the study authors. The study excluded patients suspected of having pneumonia -- for which antibiotic treatment has been shown to be beneficial -- based on their breath sounds heard using a stethoscope during a physical exam, and on the presence of a lingering fever.

The researchers did find a small benefit to antibiotic treatment: Those who took the drugs were less likely to develop new or a worsening of their symptoms compared with those who took placebos. That said, 30 patients needed to be treated with the antibiotic in order for one to experience these benefits.

“Using amoxicillin to treat respiratory infections in patients not suspected of having pneumonia is not likely to help and could be harmful,” study author Dr. Paul Little from the University of Southampton in Britain said in a statement.