That lingering cough may be annoying, but taking an antibiotic won't help in most cases, a new study shows. The study included more than 2,000 adults with coughs that had lasted at least 4 weeks. Their symptoms did not suggest they had pneumonia or another infection caused by bacteria. People were randomly divided into 2 groups. One group took the antibiotic amoxicillin for a week. The other group took placebo (fake) pills. People who got the real drugs didn't get better any faster than the placebo group. Their symptoms lasted just as long and were not any milder. But the group that got the antibiotic did have more side effects. These included nausea, rash and diarrhea. Results were similar for both younger and older adults. The journal Lancet Infectious Disease published the study online December 18. The Canadian Broadcasting Corporation and The Independent newspaper reported on the study.

By Robert H. Shmerling, M.D.
Harvard Medical School

What Is the Doctor's Reaction?

We've all been there. The cough is bad and getting worse. You feel miserable and just want to get better quickly. Yet your doctor wants to hold off on antibiotics.

As frustrating as this may be, your doctor is probably doing the right thing.

Standard antibiotics kill bacteria, but coughs often have other causes. And for some of the most common ones, antibiotics will not help.

Common causes of cough include:

• Viral infection
• Bronchitis
• Asthma
• Post-nasal drip
• Gastroesophageal reflux disease (GERD)

Each of these conditions can cause a severe cough. It can linger for weeks or even months. Yet none of these will improve any faster with antibiotics.

A new research study confirms this. More than 2,000 adults with coughs were randomly divided into 2 groups. One group took an antibiotic (amoxicillin) for a week. The other group got placebo pills. Amoxicillin was chosen because it's commonly prescribed for coughs caused by infections. Each person had a cough caused by "acute uncomplicated lower respiratory tract infection." That means their symptoms and exam did not suggest they had pneumonia or other bacterial infection.

Compared with those taking a placebo, people receiving the antibiotic:

• Did not have a shorter illness
• Had similar symptoms
• Were more likely to have side effects, such as diarrhea or rash

More people in the placebo group reported symptoms that were new or got worse. However, those differences were quite small. The findings were similar in older and younger adults.

This is just the latest (and largest) study to support more selective use of antibiotics. Avoiding the use of antibiotics that people don't need is important because they can:

• Cause side effects (which may be severe)
• Promote resistance to the drugs

Some antibiotics also are quite expensive.

Of course, this doesn't mean antibiotics are never helpful for a person with a cough. Some infections that cause cough, such as bacterial pneumonia, do require antibiotics. The challenge is to sort out which coughs need antibiotic treatment and which don't.

What Changes Can I Make Now?

If you have a cough that won't go away, contact your doctor. But don't expect to get an antibiotic every time it happens. Based on your symptoms and physical examination, your doctor may suggest blood tests or a chest X-ray. Taken together, this information will help your doctor decide whether you need an antibiotic.

Even if antibiotics won't improve your cough, other treatments may help. These include:

• Cough suppressants or cough drops
• Not smoking
• Plenty of liquids
• Decongestants or antihistamines
• Asthma treatments (including bronchodilators and inhaled corticosteroids)
• Treatments for GERD (including changes in diet and medicines that suppress acid in the stomach)
• Changing the medicines you take, as some can cause cough as a side effect.

In some cases, your doctor may recommend corticosteroids, especially if the cough might be caused by asthma or an allergic condition. The specific treatments will depend on your symptoms and medical history.

If you have shortness of breath, pink or bloody sputum, wheezing or high fever as well as a cough, see your doctor right away or get to an emergency room. You could have pneumonia or another serious condition that requires prompt treatment.

What Can I Expect Looking to the Future?

In the future, doctors may have better tests to determine which patients should be treated with antibiotics. For example, it may soon be possible to detect chemicals in the blood that the immune system produces in response to bacterial infections.

In the meantime, research such as this new study suggests that many coughs get better without antibiotics. I hope this will encourage doctors to prescribe antibiotics more selectively in the future. This research also should help patients understand why an antibiotic was not prescribed even for a particularly bad cough.