Infectious diseases

Antibiotics prevent asthma exacerbations, but at a cost


There is a clear trade off between the use of macrolides to prevent exacerbations in severe asthma and the likelihood of patients experiencing adverse events such as gastrointestinal symptoms.

Dr Chris Cates, co-ordinating editor of the Cochrane Airways Review Group in the UK, told the TSANZSRS 2019 meeting that a 2015 review of the evidence found prophylactic antibiotics had no significant impact on exacerbation rates in asthma.

However the findings changed when the results of the large Australian AMAZES trial led by Professor Peter Gibson were added to the existing data.

Dr Cates said on a number needed to treat (NNT) basis, seven patients had to be treated with azithromycin to prevent one exacerbation.

However a more recent Cochrane Review on adverse events with macrolide antibiotics highlighted the potential downsides of the drugs for some patients.

The review, comprising 183 studies with a total of 252,886 participants, found that people taking macrolides were up to twice as likely to experience gastrointestinal adverse events as people taking placebo.

Odds ratios ranged from 1.27 for vomiting, 1.61 for nausea, 1.66 for abdominal pain, 1.70 for diarrhoea to 2.16 for other non-specified gastrointestinal disorders.

Dr Cates, a primary care physician, said it was his opinion that prescribing long-term courses of macrolides for chronic respiratory diseases was the job of specialists, not GPs.

“They [specialists] don’t undertake starting people on azithromycin lightly. They screen people for atypical infections, for cardiovascular problems and other things to try and make the treatment as safe as possible and to target the people who are most going to benefit from it.”

“It needs the expert resources to monitor it and select the patients properly.”

Dr Cates said a 2018 review had shown macrolides, mostly azithromycin, could significantly reduce exacerbations in adults with bronchiectasis. There was less evidence from studies in children with bronchiectasis but the overall findings were similar.

Continuous and intermittent use of prophylactic antibiotics was also shown to reduce exacerbations in patients with COPD in another review from 2018.

The number needed to treat (NNT) in COPD to prevent one exacerbation was eight.

The COPD review also said ‘consideration of prophylactic antibiotic use should be mindful of the balance between benefits to individual patients and the potential harms to society created by antibiotic overuse’.

Dr Cates said the issue of antibiotic resistance was a concern – to the population as a whole rather than to individuals – but not well reported.

“The issue of antibiotic resistance is very difficult to quantify. We know it’s an issue and in the UK, Professor Sally Davies the Chief Medical Officer has delivered strong messages about running out of antibiotics.”

“For the most severe patients, that is a risk that we may have to take.”

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