Determination of the toxicity of intravitreal minocycline in rabbit eyes

Purpose: To evaluate the retinal toxicity of intravitreal minocycline in rabbit eyes. Methods: Intravitreal injection of minocycline with concentrations of 1000, 500, 250, 125 and 62.5 μg in 0.1 ml was performed in 10 New Zealand albino rabbits. Each concentration was injected into two rabbit eyes. For each dose, normal saline was injected in one contralateral eye and the other fellow eye remained non-injected. Electrophysiologic testing was performed before and 4 weeks after injections. The eyes were enucleated 4 weeks after injections and examined using light microscopy. Results: The clinical examination was unremarkable after injections. Electroretinography recordings were significantly affected at all doses in at least one of the a- or b-waves of photopic or scotopic responses. Histopathologic examination revealed marked atrophy and loss of integrity in all retinal layers in all minocycline injected eyes. Contralateral eyes were normal. Conclusion: In our study, intravitreal minocycline was toxic to the retina in albino rabbits even at a concentration of 62.5 µg/0.1 ml.