Objective: The clearance of ceftazidime from the rabbit vitreous cavity after injection into phakic, aphakic, and aphakic vitrectomized rabbit eyes was assessed and the duration of concentrations above the minimal inhibitory concentrations for target gram-negative bacteria was determined. To determine the effect of inflammation on the intraocular pharmacokinetics of ceftazidime, each anatomic group was subdivided into inflamed and control eyes.
Methods: Ceftazidime (2.25 mg) was into the vitreous cavity of inflamed and control rabbit eyes and its concentration was assayed 2, 8, 24, and 48 hours later. The half-life for each of the anatomic groups was calculated.
Results: The half-life of ceftazidime in control phakic eyes was 13.8 hours. In aphakic eyes the half-life was 11.8 hours and in the aphakic vitrectomized eyes the half-life was 4.7 hours. Inflammation slightly shortened the half-life in phakic (10.1 hours) and aphakic (8.7 hours) eyes. The half-life in aphakic vitrectomized inflamed eyes was 5.1 hours.
Conclusion: Vitrectomy and lensectomy significantly shorten the half-life of ceftazidime after intravitreal injection. Inflammation increases clearance to a small degree in phakic and aphakic eyes.