Vitreous cefazolin levels after intravenous injection. Effects of inflammation, repeated antibiotic doses, and surgery
D. F. Martin, L. A. Ficker, H. A. Aguilar, S. K. Gardner, L. A. Wilson and T. A. Meredith
Department of Ophthalmology, Emory University School of Medicine, Atlanta, GA 30322.
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 less than .01), but progressively
increased to 10.6 mg/L at 49 hours (P less than .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 less than .1), but progressively
increased to 24.9 mg/L at 49 hours (P less than .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.
