Intravitreal vancomycin. Retinal toxicity, clearance, and interaction with gentamicin
S. C. Pflugfelder, E. Hernandez, S. J. Fliesler, J. Alvarez, M. E. Pflugfelder and R. K. Forster
Some of the gram-positive isolates from exogenous bacterial endophthalmitis
cases treated at our institution have been found to be resistant to either
cefazolin sodium, gentamicin sulfate, or both. However, all of these
isolates have been sensitive to vancomycin. These findings prompted us to
reevaluate the retinal toxicity and clearance of intravitreal vancomycin in
pigmented rabbits. Doses up to 2 mg were found to be nontoxic in phakic and
aphakic-vitrectomized eyes. Clearance was determined in phakic and
aphakic-vitrectomized rabbit eyes with or without intact lens capsules. The
antibiotic was cleared most slowly in phakic eyes. Aphakic-vitrectomized
eyes without an intact lens capsule cleared antibiotic most rapidly, while
aphakic-vitrectomized eyes with intact capsules exhibited an intermediate
clearance rate. In addition, the interaction between vancomycin and
gentamicin on gram-positive endophthalmitis isolates was found to be
additive or synergistic depending on the bacterial species. Based on these
data, we recommend the combination of vancomycin and an aminoglycoside as
the initial antibiotic therapy for exogenous bacterial endophthalmitis.
