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Intravitreal Dexamethasone Effect on Intravitreal Vancomycin Elimination in Endophthalmitis
Susanna S. Park, MD, PhD;
Robert V. Vallar, MD;
Chian Huey Hong, MD;
Sylviane von Gunten, MD;
Kate Ruoff, PhD;
Donald J. D'Amico, MD
Arch Ophthalmol. 1999;117:1058-1062.
Objective To determine whether intravitreal dexamethasone administration can alter the elimination of intravitreal vancomycin hydrochloride in rabbit eyes with experimental Streptococcus pneumoniae endophthalmitis.
Methods Albino rabbits were infected with an intravitreal inoculum of S pneumoniae (2x103colony-forming units) and randomized after 24 hours to treatment with intravitreal vancomycin hydrochloride (1 mg), alone or in combination with intravitreal dexamethasone (400 µg). For comparison, uninfected eyes were similarly treated. All eyes were enucleated 24, 48, or 72 hours after treatment, and vitreous levels of vancomycin were quantitated using a fluorescence polarizing immunoassay.
Results The half-life of intravitreal vancomycin in infected eyes was prolonged from 48 to 84 hours when eyes were treated with dexamethasone. Conversely, such treatment shortened the half-life in uninfected eyes from 56 to 42 hours.
Conclusions Intravitreal dexamethasone administration reduces the elimination of intravitreal vancomycin in rabbit eyes with pneumococcal endophthalmitis, whereas an opposite effect is noted in uninfected eyes.
Clinical Relevance In patients with eyes having endophthalmitis caused by virulent organisms, the elimination of intravitreal vancomycin may be reduced when intraocular inflammation is minimized with corticosteroid therapy. This may enhance the efficacy of intravitreal vancomycin therapy in treating the infection.
From the Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas (Drs Park, Vallar, and Hong); and the Retina Service, Massachusetts Eye and Ear Infirmary (Drs von Gunten and D'Amico), and the Clinical Microbiology Laboratory, Massachusetts General Hospital (Dr Ruoff), Boston. Dr Park is now with the Retina Department, The Permanente Medical Group Inc, Sacramento, Calif. Dr von Gunten is now with the Department of Ophthalmology, Geneva University Hospital, Geneva, Switzerland.
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