Subconjunctival administration of ceftazidime in pigmented rabbit eyes

R. K. Shockley, P. Fishman, M. Aziz, R. A. Yannis and W. M. Jay

The ocular kinetics of ceftazidime, a third-generation cephalosporin, were examined in phakic and aphakic pigmented eyes of rabbits following subconjunctival injection (100 mg). Peak ceftazidime concentrations (mean +/- SE, n = three to five rabbits per determination) were as follows: phakic eyes, 40.2 +/- 7.3 mg/L in aqueous humor and 11.2 +/- 0.6 mg/L in vitreous humor at one hour; aphakic eyes, 30.5 +/- 4.8 mg/L in aqueous humor and 15.8 +/- 2.4 mg/L in vitreous humor at one hour. The ability of ceftazidime to eliminate an incipient bacterial infection was also studied. Ten aphakic rabbits received intravitreal injections of 50 colony-forming units (cfu) of Pseudomonas aeruginosa. Six of the ten immediately received a subconjunctival injection of ceftazidime (100 mg). At 48 hours following injections, four of four control eyes yielded bacterial counts greater than 6.2 X 10(6) cfu/mL. Of the six that received ceftazidime, five were sterile and one yielded 10 cfu/mL.