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

Background: A prospective study was undertaken to determine the transcorneal penetration of three topically applied fluoroquinolones into aqueous humor.
Methods: Cataract patients (n = 224) preoperatively received topically applied gyrase inhibitors (0.3% ciprofloxacin, 0.3% norfloxacin, 0.3% ofloxacin) in two different application modes. In application mode I, patients received on the day before operation 3 x 1 eye drop at 2-h intervals, and on the day of operation 3 drops at 1-h intervals. In application mode II, patients received 9 drops at 15-min intervals on the day of operation only. Just before cataract surgery 50-100 ml 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 between 06:00 and 08:00 hours before operation. In this mode, ciprofloxacin achieved a mean aqueous level of 379.8 +/- 327.8 mg/l (range 33-1388 mg/l), norfloxacin 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 MIC90 of gram-negative bacteria like Proteus mirabilis and Escherichia coli. In some cases the concentrations of ciprofloxacin and ofloxacin, but never norfloxacin, reached therapeutic values above the MIC90 of Staphylococcus aureus 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 available topical fluoroquinolones, ofloxacin achieved the highest aqueous humor concentration. Considering the higher antimicrobial activity of ciprofloxacin, both ciprofloxacin and ofloxacin may be useful ophthalmic agents in antibacterial management, but they are not efficient against Streptococcus pneumoniae and Pseudomonas aeruginosa.