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V.L. Morrison, H.J. Koh, L. Cheng, K. Bessho, W.R. Freeman; Intravitreal Toxicity of the Kenalog Vehicle (Benzyl Alcohol) in Rabbits . Invest. Ophthalmol. Vis. Sci. 2004;45(13):1917.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: The use of commercially available triamcinolone acetate (Kenalog) for macular edema and other intraocular diseases has been controversial in part because of adverse effects of the drug. We hypothesized that the preservative in the commercial compound was toxic to the eye and wished to test this hypothesis in an animal model. Methods: Nine New Zealand rabbits were injected with either a control or test article at elevating concentrations. The test article was benzyl alcohol calculated to give final injected concentrations of 0.0073%, 0.022%, 0.073%, 0.222%, 0.733% benzyl alcohol. This corresponds to one–half log below, the same, and one–half log above the concentration of benzyl alcohol in human eyes when 0.1cc of commercial Kenalog is used. Results: We found that concentrations of benzyl alcohol only 3.3 times higher than what is injected intravitreally in humans is toxic to the retina and that higher concentrations is extremely toxic. Changes occurred largely in the outer retina and included loss and shortening of outer segments and photoreceptors. At higher concentrations exudative retinal detachment was seen. Conclusions: Benzyl alcohol at concentrations modestly higher than what is present in commercial Kenalog is toxic to the eye. This has been shown in other organ systems. If commercial preserved Kenalog is to be used clinically, decanting or other means to remove the benzyl alcohol should be considered. We hypothesize that the non infectious inflammation seen clinically after Kenalog injection is due to the presence of a toxic preservative at unsafe concentrations.
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