title: Oxacillin for bacterial endophthalmitis: subconjunctival, intravenous, both, or neither?
abstract: We compared the intraocular concentrations of oxacillin given by continuous intravenous infusion, subconjunctival injection, or combined therapy in a rabbit model of Staphylococcus aureus endophthalmitis. At equilibrium during intravenous infusion, concentrations in the aqueous humor, cornea, and choroid-retina were 25% to 30% of the serum level; in contrast, vitreous levels were only 2% of the serum concentration. Subconjunctival injection produced extremely high levels in the cornea and aqueous and moderate concentrations in the choroid-retina; vitreous penetration remained poor (<1 microgram/ml). Combined therapy offered little advantage in terms of concentrations in the aqueous or cornea and had a modest effect on levels in the choroid-retina. Vitreous concentrations showed a striking relation to serum levels with all regimens, including subconjunctival ones; although this could have been fortuitous, it suggests an important role for the hematogenous route in this model. Only those modes of delivery producing serum concentrations greater than 50 micrograms/ml consistently resulted in vitreous levels greater than 0.4 microgram/ml. The optimal therapy of bacterial endophthalmitis may require direct intravitreal injection of antibiotic.
mesh_terms: D000818:Animals; D001082:Aqueous Humor / Q000032:analysis; D002829:Choroid / Q000032:analysis; D003228:Conjunctiva; D003315:Cornea / Q000032:analysis; D009877:Endophthalmitis / Q000188:drug therapy*; D007263:Infusions, Parenteral; D007267:Injections; D010068:Oxacillin / Q000032:analysis / Q000097:blood / Q000627:therapeutic use*; D011817:Rabbits; D012160:Retina / Q000032:analysis; D013203:Staphylococcal Infections / Q000188:drug therapy*; D014822:Vitreous Body / Q000032:analysis
chemical_list: D010068:Oxacillin