An ophthalmic formulation of the popular antibiotic azithromycin is now on the market for the treatment of bacterial conjunctivitis.
Azithromycin ophthalmic solution 1% (AzaSite, Inspire Pharmaceuticals) is a topical formulation of the popular antibiotic that has been combined with drug-delivery technology (DuraSite, InSite Vision) to create a stable aqueous formulation. The component increases the bioavailability of the azithromycin, and the combination should allow physicians to have an impact on the care of their patients through a high and sustained level of antibiotic activity at the site of the infection, said William B. Trattler, MD, in private practice at the Center for Excellence in Eye Care, Miami.
The broad-spectrum antibiotic received FDA approval in April for the treatment of bacterial conjunctivitis caused by susceptible isolates of CDC coryneform group G, Haemophilus influenzae, Staphylococcus aureus, Streptococcus mitis group, and Streptococcus pneumoniae.
"What's exciting . . . is that essentially all of the advantages of the oral preparation carry over to the topical preparation as well," said Eric D. Donnenfeld, MD, co-director, cornea, Nassau University Medical Center, New York. "It offers incredible safety and efficacy, and what really separates it from other antibiotics is that it achieves therapeutic levels with once-a-day dosing. It's the first time that an ophthalmic eye drop can achieve high tear film levels that are maintained for a 24-hour period."
The ophthalmic formulation of azithromycin also represents a major reduction in the frequency and number of drops required to resolve bacterial conjunctivitis, said Dr. Donnenfeld, who also is founding partner, Ophthalmic Consultants of Long Island, Rockville Centre, NY.
The typical course of azithromycin is one drop twice a day for 2 days, followed by one drop a day for the next 5 days-a total of nine drops per affected eye. In comparison, the total drops indicated per course of other commonly used antibiotics: 0.5% moxifloxacin (Vigamox, Alcon Laboratories), 21 drops; 0.3% tobramycin (Tobrex, Alcon), 28 drops; and trimethoprim sulfate and polymyxin B sulfate (Polytrim, Allergan), 42 drops.
The compliance issue may give azithromycin an edge over other topical antibiotics in some cases.
"What we've learned . . . is that once you reduce the dosing schedule, patient compliance improves dramatically and you get better results," Dr. Donnenfeld said. "The same lessons will apply to antibiotic therapy and, specifically, to azithromycin if you have an antibiotic that's as effective or more effective when being dosed once a day as a drop being used four times a day."
"Since it has excellent coverage for bacterial conjunctivitis, if you're concerned about how compliant a patient might be, this is a very good choice," Dr. Trattler said.