Microbiologic Efficacy of 3-day Treatment with Azithromycin 1.5% Eyedrops for Purulent Bacterial Conjunctivitis

PURPOSE: Antibacterial efficacy of topically applied azithromycin 1.5% was compared with tobramycin 0.3% in a multicenter, randomized, investigator-masked study for the treatment of purulent bacterial conjunctivitis. METHODS: A total of 1043 adults and children received either azithromycin twice daily for 3 days (n=524) or tobramycin every 2 hours while awake for 2 days, then four times daily for 5 days (n=519). Conjunctival swabbing was taken at days 0, 3, and 9, using alginate swabs resuspended in a dissolution-transport medium, providing rapid and reproducible results. Cagle's criteria were used to define the pathogenicity level for each isolated bacterium. RESULTS: In the per-protocol set, the rate of bacteriologic resolution was 85.2% for azithromycin versus 83.8% for tobramycin on day 3, and 92.8% for azithromycin versus 94.6% for tobramycin on day 9. Azithromycin was demonstrated to be noninferior to tobramycin according to the 10% noninferiority margin. Although some bacteria were categorized as resistant to tested antibiotics, eradication was observed (for azithromycin: Acinetobacter, Enterobacteriaceae, Pseudomonas), highlighting the specific pharmacokinetics/pharmacodynamics of the ocular route. CONCLUSIONS: In total, topical therapy with azithromycin 1.5% administered only twice daily for 3 days effectively eradicates most pathogenic bacteria associated with bacterial conjunctivitis. These microbiologic results are in accordance with the observed clinical outcome. This new anti-infective product has the advantage of a short treatment course which could lead to an improvement in patient compliance.