[Retinotoxicity of intravitreous injection of cefmenoxime]

The semisynthetic third generation cephalosporin cefmenoxime was injected through the pars plana into the mid-vitreous in seven rabbit eyes. The drug dosage varied between 0.5 and 15 mg. Seven control eyes were injected only with 0.9% NaCl-solution. Electroretinography was performed before injection and 1 week post injection. The rabbits were anesthetized by intramuscular application of ketanine (Ketanest). Immediately after the second ERG the eyes were enucleated and prepared for both light and electron microscopy. Light microscopy showed only slight retinotoxic effects. Electron microscopy revealed beginning toxic necrosis of the outer segments of the photoreceptors following drug doses equal to or greater than 2 mg. Significant changes in the ERG were not noted in any of the treated eyes. The toxicity of cefmenoxime and other cephalosporins reported in the literature is discussed together with the clinical relevance of the findings.