Abstract
Abstract: :
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 anterior chamber of the eye compared to topical application. Methods: Using a New Zealand white rabbit model, we compared the moxifloxacin concentration in the aqueous humor achieved 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 anterior chamber antibiotic concentration following a single subconjunctival application. At the end time points, the animals were euthanized and a 27–gauge needle was used to enter the anterior chamber through the cornea and aspirate 1–2 mL of aqueous fluid. Samples were kept frozen at –80C until analysis by HPLC. Results: The average concentration of moxifloxacin in the experimental group with hourly topical drops for 7 hours was 2325 ng/mL. The average concentration of antibiotic at 2 hours following one subconjunctival injection was 754.5 ng/mL. The remaining groups had concentrations below the quantitation limit of 25 ng/mL. Conclusions: With topical application the concentration of moxifloxacin established is above the minimal inhibitory concentration for even fluoroquinolone–resistant gram–positive bacteria, but administration of the antibiotic via subconjunctival injection is probably not as effective as frequent topical application. These results would not support replacing topical application of fluoroquinolone with subconjunctival injection.
Keywords: antibiotics/antifungals/antiparasitics