Abstract
Introduction: :
From the Department of Ophthalmology and the Francis I. Proctor Foundation, University of California San Francisco, USA
Purpose: :
Standard therapy for corneal ulcers consists of hourly application of antibiotic drops. However, this regimen is often difficult to adhere to, especially in systemically ill and elderly patients. We wish to determine whether subconjunctival injection of moxifloxacin will achieve comparable or higher antibiotic concentration in the cornea compared to topical application.
Methods: :
Using a New Zealand white rabbit model, we compared the moxifloxacin concentration in the cornea after single and repeated topical applications versus one time subconjunctival delivery. The experimental groups consisted of: 8 eyes receiving one 30 uL topical drop every hour for 7 hours followed by sampling at 8 hours; 8 eyes receiving one 30 uL topical drop once only followed by sampling at 8 hours; 4 sets of 6 eyes receiving a 0.1 mL subconjunctival injection once followed by the sampling of one set at 2, 8, 12, and 24 hours in order to establish a decay curve of corneal antibiotic concentration following a single subconjunctival application. At the end time points, the animals were euthanized and the corneas harvested for maceration and HPLC analysis. Samples were kept frozen at –80C until analysis.
Results: :
The highest mean corneal concentration of moxifloxacin was achieved by hourly application of topical drops at 8 hours: 52.33 ng/g (SD 58.63). The mean corneal concentration of antibiotic at 2 hours following one subconjunctival injection was substantially lower: 4.48 ng/g (SD 3.02). The corneal concentration of antibiotic at 2 hours following subconjunctival injection was not found to be any higher than the corneal concentration at 24 hours following topical application (4.48 ng/g SD 3.02 versus 4.39 mg/g SD 6.04)
Conclusions: :
Administration of antibiotic via subconjunctival injection is probably not as effective as frequent topical application for treatment of corneal infection. Subconjunctival injection should not be considered an effective substitute for, or augmentation of, topical antibiotic application. These results support the recommendation of frequent topical application of antibiotics for the treatment of corneal infection.
Keywords: cornea: basic science • antibiotics/antifungals/antiparasitics • drug toxicity/drug effects