"A lot of people with uncomplicated colds and infections really have a virus, and antibiotics don't do anything for viruses," commented Dr. Jordan S. Josephson, an ear, nose, throat and sinus specialist at Lenox Hill Hospital in New York City. "This [study] confirms what we always knew; that there are some infections for which you need antibiotics, and antibiotics are terrific in those cases. There are other infections for which you don't need antibiotics, and the common cold is one of those."

"This is consistent with previous research, but it is more compelling and more convincing," added Dr. Mark H. Ebell, author of an accompanying editorial and an associate professor of family practice at Michigan State University in East Lansing. "The number of patients studied is as many as have been in all of the previous studies combined, and they followed the patients for a little longer period of time."

Different Prescribing Strategies

According to the article, which appears in the June 22/29 issue of the Journal of the American Medical Association, acute lower respiratory tract illness is the most common condition treated in primary care. In the United States, experts estimate that unnecessary antibiotic prescriptions total $726 million per year.

The growing threat of pathogens resistant to common antibiotics has also prompted experts to urge that doctors cut back on the use of these drugs against viral illnesses (such as the common cold) for which they are useless.

For this study, researchers looked at different prescribing strategies, including the value of handing out informational leaflets to people suffering from these common lower respiratory illnesses.

About 800 patients were randomized to receive a leaflet or no leaflet, or to receive immediate antibiotics, no offer of antibiotics or delayed antibiotics.

In general, the participants had an illness that was a little more serious than an ordinary cold, Ebell said.

Seventy percent of the participants also returned diaries documenting their illness, and 10 percent provided information about symptom duration and severity.

The information leaflet had no effect on the main outcomes, namely duration and severity of symptoms including cough. Giving an antibiotic immediately vs. offering a prescription for later generally did not alter cough duration or other primary outcomes, they add.

"There may be a minor benefit (one day of moderately severe illness for an illness lasting three weeks on average)," said study author Dr. Paul Little, a professor of primary care research at the University of Southampton in Highfield, England. "The challenge will be to find the subgroup of patients who really do benefit."

Clearly, patients who have pneumonia need to be considered for antibiotics, he added.

'An Annoying Illness'

The study also provided better information on the natural history of such illnesses: they tend to last three weeks, with 10 days of symptoms before visiting a doctor and 12 days after.

The remaining challenge will be convincing doctors and patients alike not to use antibiotics when they're not likely to be helpful. In this study, fewer patients who received an offer of delayed antibiotics reported being "very satisfied."

"Doctors need to be sympathetic and warn patients that unfortunately this is an annoying illness that will go on for, on average, another two weeks, and that studies suggest that at most you will get a day's difference from antibiotics," Little said. "The good news is that most patients only feel really rough for the first five to seven days after seeing the doctor."

"The challenge is that it sometimes feels easier to just write a quick prescription," Ebell added. "I think the more helpful dialogue would be with the patient who understands antibiotics are not always needed, and the physician who only uses antibiotics when they are really likely to help the patient feel better faster."

More information: The Alliance for the Prudent Use of Antibiotics has information on the consequences of overprescribing antibiotics.