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A phase III clinical trial showed that a new ocular solution of azithromycin 1%, formulated with a patented delivery vehicle, significantly shortened the time to clinical resolution and bacterial eradication of infectious bacterial conjunctivitis when used as primary therapy for 5 days.
Bacterial conjunctivitis is primarily caused by Haemophilus influenzae, Staphylococcus aureus, and Streptococcus pneumoniae. Even though the natural course of bacterial conjunctivitis is short-from 8 to 10 days-antibiotics frequently are prescribed to hasten the patient's recovery, reduce the risk of spreading the infection to other individuals and the chance of sequelae, and prevent the possibility of recurrence of the infection, he reported.
Dr. Abelson is an associate clinical professor of ophthalmology at Harvard Medical School and a senior clinical scientist at Schepens Eye Research Institute, Boston.
Azithromycin is a broad-spectrum drug that is active against gram-positive, gram-negative, and atypical bacteria. This new ocular solution of 1% azithromycin (Aza-Site, InSite Vision) is delivered with a novel ocular delivery system (DuraSite, InSite Vision) and "stays in contact with the conjunctiva and delivers active drug to the ocular surface over a period of several hours," he said. "These attributes support a simplified and short therapeutic regimen that delivers high bactericidal concentrations of azithromycin to the site of the infection."
The azithromycin 1% solution was evaluated for safety and efficacy in the treatment of bacterial conjunctivitis during a multicenter, double-masked clinical study with a control group, which was conducted at 69 centers in the United States, Mexico, Guatemala, and the Dominican Republic. The study duration was 6 days, with three visits. The drug was administered twice daily on days 1 and 2 and once daily on days 3 through 5.
The investigators recorded the clinical signs and obtained specimens for bacterial culture at baseline and at two follow-up visits. Patients were included if they were aged 1 year or more.
Other inclusion criteria included a clinical diagnosis of bacterial conjunctivitis with symptoms of less than 3 days duration and a best-corrected visual acuity of 20/100 or better. Bacterial conjunctivitis was confirmed by laboratory testing.
Patients were excluded if they had debilitating disease, previous or concomitant use of any antibiotic or topical ophthalmic solution, suspected viral or allergic conjunctivitis, or a positive pregnancy test. The clinical study was designed and conducted in concert with Ophthalmic Research Associates, North Andover, MA.
The primary study endpoint was clinical resolution of the bacterial conjunctivitis at the third visit. Clinical resolution was defined as the absence of all clinical signs such as conjunctival discharge and bulbar and palpebral conjunctival injection.
A total of 279 patients were evaluated for efficacy. The mean age was 28.4 years (range, 1 to 96 years). The results indicated that, at the third visit on day 6, 63.1% of the subjects randomly assigned to receive azithromycin had clinical resolution compared with only 49.7% of the participants randomly assigned to receive the vehicle (p = 0.030). The rate of bacterial eradication in the study population at the third visit was 88.5% in those who received azithromycin and 66.4% in those who received the vehicle (p < 0.001), according to Dr. Abelson.
"Azithromycin 1% ophthalmic solution in [the novel ocular delivery system] successfully eradicated pathogens that were resistant to azithromycin and other antibiotics used in commercial eye drops," he said. "Regarding both clinical cure and bacterial eradication, [this topical agent] offers physicians an additional ocular antibiotic choice that competes very favorably with current eye drop treatments."