Azithromycin cleared the bacteria in wheezing preschoolers and made no difference to their symptoms

Design

multicentre, randomised, placebo-controlled trial stopped for futility at planned interim analysis (AZ-SWED)

Population

840 children aged 18-59 months presenting to an emergency department with moderate-to-severe wheezing; 521 positive for pathogenic bacteria

Primary outcome

sum of Asthma Flare-up Diary for Young Children scores over 5 days (range 5-35)

Effect

median 9.59 vs 9.72 in the bacteria-positive cohort (P = 0.70) and 9.30 vs 9.10 in the negative cohort (P = 0.69); bacterial clearance 58.7% vs 11.4%

AZ-SWED randomised 840 children aged 18 to 59 months presenting to emergency departments with moderate-to-severe wheezing to azithromycin 12 mg/kg once daily for five days or matching placebo. Efficacy was assessed separately in the 521 who tested positive for Streptococcus pneumoniae, Moraxella catarrhalis or Haemophilus influenzae and in those who did not. The data and safety monitoring board stopped the trial for futility at a planned interim analysis.

Symptom scores over five days were essentially identical in every comparison. What makes this trial useful rather than merely negative is the microbiological result alongside it: azithromycin cleared the target bacteria in 58.7% of the positive cohort against 11.4% on placebo. The drug did what it was supposed to do to the organisms, and the children were no better for it.

That dissociation is the finding worth carrying. The rationale for antibiotics in preschool wheeze rested on observational work showing these organisms more often in children with recurrent wheezing. This trial shows that association was not causal, and it does so by eliminating the obvious alternative explanation — treatment failure.

Wheezing preschoolers are among the commonest paediatric antibiotic prescriptions in Indian emergency practice, and macrolide resistance in S. pneumoniae here is already high. A prescription that provides no benefit is not neutral in that context.

• Do not prescribe azithromycin for an acute wheezing episode in a preschool child without a separate bacterial indication
• A positive nasopharyngeal culture in this setting is not an indication — the bacteria-positive children did no better
• Treat the wheeze: bronchodilator and, where indicated, corticosteroid, as before
• Give parents an explicit reason why no antibiotic is being given, or the prescription simply moves to the next clinician
• Reserve antibiotics for a documented focus — otitis media, pneumonia on examination or imaging

The statistics, in plain English

The primary outcome was a five-day symptom diary score ranging from 5 to 35; medians were 9.59 against 9.72 in the bacteria-positive cohort and 9.30 against 9.10 in the negative cohort, with p-values of 0.70 and 0.69 — differences well inside the spread of the interquartile ranges. Stopping for futility means the monitoring board judged that continuing could not plausibly produce a positive result, which is a stronger statement than simply failing to reach significance. The bacterial clearance difference, 58.7% against 11.4%, shows the trial was not undermined by inadequate drug exposure.

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