Objective To determine if preoperative topical administration of ciprofloxacin or ofloxacin results in aqueous humor drug concentrations that exceed the MIC90 of common ocular contaminants in dogs undergoing cataract surgery.
Procedures Twelve dogs were treated with topical 0.3% ciprofloxacin and 13 dogs with topical 0.3% ofloxacin once the night before surgery, and then with 1 drop of ciprofloxacin or ofloxacin every 15 min for 2 h immediately before surgery. Aqueous humor samples were taken from each eye immediately before the incision was made and frozen at −70 °C. First eye samples (S1) were taken closer to the time of topical treatments than second eye samples (S2). Samples were analyzed by high performance liquid chromatography (HPLC) at the North Carolina State University (NCSU) Clinical Pharmacology laboratory.
Results In ciprofloxacin patients, S1 concentrations were 0.03–0.69 (0.17 median) µg/mL, and S2 concentrations were 0.09–0.95 (0.36 median) µg/mL. Aqueous humor concentrations did not exceed the MIC90 of Streptococcus sp. Few eyes (1/12 OU) exceeded the MIC90 for Staphylococcus sp. or Corynebacterium sp.; moderate numbers (5/12 S1; 8/12 S2) exceeded the MIC90 for E. coli. In ofloxacin patients, S1 concentrations were 0.48–2.81 (1.05 median) µg/mL, and S2 concentrations were 0.45–3.63 (1.30 median) µg/mL. Although few eyes (≤ 2/13 OU) exceeded the MIC90 for Streptococcus sp. or Corynebacterium sp., moderate numbers (7/13 S1, 9/13 S2) exceeded the MIC90 for Staphylococcus sp. and most eyes (12/13 OU) exceeded the MIC90 for Bacillus sp. All eyes exceeded the MIC90 for E. coli.
Conclusions Ofloxacin has higher corneal penetration and ability to exceed MIC90 of common ocular contaminants than ciprofloxacin, and would be a more appropriate prophylactic choice for canine cataract patients.