VITREOUS CEFAZOLIN LEVELS AFTER INTRAVENOUS-INJECTION - EFFECTS OF INFLAMMATION, REPEATED ANTIBIOTIC DOSES, AND SURGERY

We devised a standardized rabbit model of intraocular inflammation using heat-killed Staphylococcus epidermidis as the inducing organism. We applied this model to study the effects of (1) inflammation, (2) repeated antibiotic doses, and (3) surgical status of the eye on cefazolin levels in the vitreous cavity after intravenous administration. Intravenous cefazolin sodium, 50 mg/kg, was administered every 8 hours for 48 hours. Eyes were harvested for assay of vitreous cavity antibiotic levels at various intervals from 1 to 49 hours. Drug levels were compared in inflamed and noninflamed eyes under both phakic and aphakic/vitrectomized conditions. At 1 hour, levels in phakic specimens were 3.0 mg/L in inflamed eyes vs undetectable in noninflamed eyes (P <.01), but progressively increased to 10.6 mg/L at 49 hours (P <.02) in inflamed eyes only. Levels in aphakic/vitrectomized eyes at 1 hour were 6.7 mg/L in inflamed eyes vs 4.2 mg/L in noninflamed eyes (P<.1), but progressively increased to 24.9 mg/L at 49 hours (P <.001) in inflamed eyes only. Levels at 49 hours in inflamed phakic and inflamed aphakic/vitrectomized eyes were well above the minimum inhibitory concentrations for organisms termed sensitive to cefazolin. We would conclude, therefore, that repeated doses of intravenous cefazolin may play an important adjunctive role in the treatment of endophthalmitis. © 1990, American Medical Association. All rights reserved.