Penetration of topical and oral ciprofloxacin into the aqueous and vitreous humor in inflamed eyes.

PURPOSE: To assess the aqueous and vitreous penetration of ciprofloxacin after topical and combined topical and oral administration and investigate the effects of inflammation on drug penetration. METHODS: A standardized penetrating injury was made in the right eyes of 16 rabbits. Intraocular inflammation was induced by intravitreal injection of a suspension of Staphylococcus aureus in these eyes. The animals were divided into two groups according to treatment methodology: topical and topical-oral. The intact left eyes of the animals were maintained as controls. In the topical treatment group, two drops of ciprofloxacin 0.3% were instilled to both eyes every 30 minutes for 4 hours. In the topical-oral treatment group, animals were given two oral 40 mg/kg doses of ciprofloxacin at 12-hour intervals. After the last oral dose, the protocol of the topical group was applied to these eyes. Half an hour after the last drop, 100-microL samples were taken from aqueous and vitreous humor of all eyes. Drug concentrations were measured using high-pressure liquid chromatography. RESULTS: Mean aqueous levels of ciprofloxacin in control eyes were 2.31 microg/mL (range, 1.02-6.27 microg/mL) in the topical group and 5.88 microg/mL (1.52-17.81) in the topical-oral group. Mean aqueous levels in inflamed eyes were 7.36 microg/mL (2.34-17.15) in the topical group and 14.43 microg/mL (2.18-18.66) in the topical-oral group. Mean vitreous levels in control eyes were 0.77 microg/mL (0.09-1.93) in the topical group and 1.01 microg/mL (0.49-1.57) in the topical-oral group. Mean vitreous levels in inflamed eyes were 0.95 microg/mL (0.18-1.27) in the topical group and 1.98 microg/mL (0.51-3.34) in the topical-oral group. There was no significant difference among the groups (P > 0.05). Mean aqueous levels in all eyes and mean vitreous levels in the combined topical and oral group of inflamed eyes were above the 90% minimum inhibitory concentration for most of the common microorganisms causing endophthalmitis. CONCLUSION: There is an increase in both aqueous and vitreous humor concentrations with inflammation and with oral and topical administrations, as opposed to topical only, of ciprofloxacin. Using oral as well as topical treatment may be a beneficial method of antibiotic prophylaxis in ocular trauma once a patient has received intravenous or intravitreal therapy.