Penetration of ciprofloxacin, norfloxacin and ofloxacin into the aqueous humor using different topical application modes

Background: A prospective study was undertaken to determine the transcornea l penetration of three topically applied fluoroquinolones into aqueous humo r. Methods: Cataract patients (n=224) preoperatively received topically applie d gyrase inhibitors (0.3% ciprofloxacin, 0.3% norfloxacin, 0.3% ofloxacin) in two different application modes. In application mode I, patients receive d on the day before operation 3x1 eye drop at 2-h intervals, and on the day of operation 3 drops at l-h intervals. In application mode II, patients re ceived 9 drops at 15-min intervals on the day of operation only. Just befor e cataract surgery 50-100 mi aqueous humor was aspirated and stored at -80 degrees C. The HPLC method was used for measuring the concentration. Results: The highest concentrations of all tested antibiotics were measured after the mode of application in which one drop was given every 15 min bet ween 06:00 and 06:00 hours before operation. In this mode, ciprofloxacin ac hieved a mean aqueous level of 379.8+/-327.8 mg/l (range 33-1388 mg/l), nor floxacin 182.1+/-118.1 mg/l (range 38-480 mg/l) and ofloxacin 563.9+/-372.1 mg/l (range 64-1455 mg/l). These mean concentration are all above the MIC9 0 of gramnegative bacteria like Proteus mirabilis and Escherichia coli. In some cases the concentrations of ciprofloxacin and ofloxacin, but never nor floxacin, reached therapeutic values above the MIC90 of Staphylococcus aure us and Staphylococcus epidermidis Conclusions: The mean concentration value of 0.3% ciprofloxacin and of 0.3% ofloxacin in the aqueous humor reached the MIC90 values of the frequently occurring gram-positive and gram-negative bacteria. Of the currently availa ble topical fluoroquinolones, ofloxacin achieved the highest aqueous humor concentration. Considering the higher anti-microbial activity of ciprofloxa cin, both ciprofloxacin and ofloxacin may be useful ophthalmic agents in an tibacterial management, but they are not efficient against Streptococcus pn eumoniae and Pseudomonas aeruginosa.