Effect of paracentesis on ocular cloxacillin concentration

Intraocular levels of cefuroxime in uninflamed rabbit eyes

Intraocular levels of cefuroxime following subconjunctival, intravitreal and combined intravitreal and intravenous administration were determined in uninflamed rabbit eyes. Intraocular levels of the antibiotic were assayed by a biological method. Penetration of cefuroxime into the vitreous following subconjunctival administration was poor. Subconjunctival administration produced higher levels of cefuroxime in the aqueous when compared to parenteral administration alone. Higher levels of cefuroxime were achieved both in the aqueous and in the vitreous after an intravitreal injection. Intravitreal injection of 100 and 1000 micrograms cefuroxime produced intravitreal levels close to the minimum inhibitory concentration (MIC) for most ocular pathogens up to 24 h after drug administration. Intravenous supplementation did neither enhance the intraocular levels nor did it delay the clearance of the intravitreally injected antibiotic. Mild histopathological changes were seen with equal frequency both in the control and the test eyes and are attributed to the sampling techniques. Electroretinography (ERG) showed no definite changes suggestive of retinal toxicity up to 55 days after intravitreal administration.

Cloxacillin distribution in the rabbit eye after intravenous injection

Distribution of isotopically labelled and intravenously injected cloxacillin was studied in rabbit eye. The antibiotic concentration determined by liquid scintillation counting proved to be a reliable measure of the total antibiotic concentration when controlled by microbiological assay. In the rabbit eye after an intravenous injection of 50 mg/kg of cloxacillin sodium, longlasting antibiotic concentration regarded as therapeutic against penicillinase producing staphylococci was obtained in all vascularized ocular structures and in the cornea. The antibiotic present in the iris and ciliary body, and in the retina and choroid preparations, proved to be partly intravascular, whereas it penetrated better into the extravascular tissue compartment of the sclera and limbal area. Cloxacillin failed to achieve a therapeutic antibiotic concentration in the vitreous body and in the lens. Administration of probenecid had an enhancing effect on ocular cloxacillin concentration allowing improved drug diffusion into the eye by means of an elevated plasma concentration. No specific ocular effect of probenecid was noticed. Therapeutic concentration of cloxacillin in the aqueous humour, otherwise barely achieved, was more satisfactorily obtained with a previous injection of probenecid.