Objective: Vancomycin hydrochloride for intraocular injection is the d
rug of choice for the treatment of suspected gram-positive endophthalm
itis. To study its intraocular pharmacokinetics, we injected vancomyci
n into the vitreous cavity of phakic, aphakic, and aphakic-vitrectomiz
ed rabbit eyes and determined its rate of clearance. Inflamed eyes wer
e compared to control eyes in each group. Methods: Three groups of eye
s were prepared. The eyes in Group 1 were phakic, the eyes in Group 2
had the lens removed, and the eyes in Group 3 had both the lens and ce
ntral vitreous removed. Each group was subdivided into a control group
and a group made inflamed by injection of heat-killed Staphylococcus
epidermidis. Vancomycin hydrochloride 1 mg in 0.1 cc of diluent was in
jected into the midvitreous cavity and samples obtained at 2 or 3, 8,
24, and 48 hours after injection. Vancomycin concentrations were measu
red and clearance rates were calculated for each of the groups. Result
s: Vancomycin was cleared substantially faster from aphakic-vitrectomi
zed eyes (half-life 9.0 hours) and aphakic eyes (half-life 8.9 hours)
than phakic eyes (half-life 25.1 hours). inflammation increased the ra
te of elimination of vancomycin only in the aphakic group. Conclusions
: Clearance of vancomycin from the phakic eye is prolonged compared to
that of beta-lactam antibiotics, an important pharmacokinetic advanta
ge in treating endophthalmitis, its clearance from aphakic-vitrectomiz
ed eyes is dramatically faster than from phakic eyes and is similar to
that of other antimicrobial agents.