Chest infections are very common at this time of year. However, a new study has found that an antibiotic commonly prescribed for some of these infections does not work, even in older patients.

The study focused on common lower respiratory tract infections (LRTI), such as bronchitis and the effect of the antibiotic, amoxicillin.

According to UK scientists, LRTIs are one of the most common acute illnesses seen by GPs. While most of these infections are thought to be caused by viruses - which antibiotics have no effect on - the use of the drugs in treating them is a topic of major debate. To date, research results have been conflicting.

The team from the University of Southampton looked at over 2,000 adults with acute, uncomplicated LRTIs from 12 European countries, including England, Wales, Germany, Sweden Spain and Poland.

The participants were randomly assigned to receive either amoxicillin or a placebo three times a day for seven days. They were monitored throughout.

The study found that there was little difference in the duration or severity of the symptoms between the two groups. This was true even for patients over the age of 60.

While more patients in the placebo group reported new or worsening symptoms, just two from that group, along with one from the antibiotic group, needed to be hospitalised because of the LRTI.

Furthermore, patients in the antibiotic group reported more side-effects, such as diarrhoea, nausea and rash, than those in the placebo group.

"Our results show that most people get better on their own. But, given that a small number of patients will benefit from antibiotics, the challenge remains to identify these individuals," commented Prof Paul Little of the University of Southampton.

He added that using amoxicillin to treat respiratory infections in patients not suspected of having pneumonia ‘is not likely to help and could be harmful', particularly if it leads to antibiotic resistance.

Details of these findings are published in the journal, The Lancet Infectious Diseases.