Intravitreal injection of piperacillin.

Piperacillin was injected into the vitreous body of rabbit eyes to evaluate its suitability for intraocular injection and its toxicity on intraocular tissues. Doses ranged from 50 micrograms to 3,000 micrograms. Toxicity was determined through histology and electroretinograms by comparing the piperacillin-injected eyes with eyes injected with balanced saline solution. Retinal toxicity was noted in the outer layer of the retina when 3,000 micrograms was injected intravitreally. No toxicity was noted by histology with 1,500 micrograms of piperacillin. The minimal inhibitory concentration of piperacillin is 800 micrograms/cc for both gram negative and gram positive organisms. The large dose of intravitreal piperacillin tolerated by rabbit eyes makes piperacillin a potentially safe and effective broad spectrum antibiotic for the treatment of bacterial endophthalmitis in human eyes.