Determination of Safety of Escalating Doses of subconjunctival doxycycline in Rabbit Eyes

Purpose: To determine the maximum non-toxic dose of subconjunctival doxycycline in rabbit eyes Methods: Eight rabbits (sixteen eyes) were scheduled for evaluating side effects of four subconjunctival doses of 250, 500, 1000 and 2000 IU of doxycycline, two rabbits for each dose. For each dose (two rabbits), the drug was injected for the right eyes. Balanced salt solution (BSS) was injected into the left eye of one rabbit (placebo eye) and the other left eye remained uninjected (control eye). All eyes were examined in 1, 2, 3, 7, 14 and 28 days after intravitreal injections. After four weeks, animals were euthanized and eyes were enucleated and submitted for Hematoxylin & Eosin (H&E) and histology evaluations.Results: anterior segment inflammatory reactions like hyperemia and chemists were observed after injections and were grading. H&E staining and histology examinations did not revealed any sign ofconjunctival toxicity with injected doses.Conclusion: subconjunctival injection of doxycycline in rabbit eyes was not associated with adverse toxic effects up to 2000 IU doses