PENETRATION OF CIPROFLOXACIN, NORFLOXACIN AND OFLOXACIN INTO THE AQUEOUS-HUMOR OF PATIENTS BY DIFFERENT TOPICAL APPLICATION MODES

Objectives: A prospective study was undertaken to determine the transc orneal penetration of three topically applied fluoroquinolones into aq ueous humour. Methods: Two hundred and twenty-four patients undergoing cataract extraction received 0.3% ciprofloxacin, norfloxacin or oflox acin eye drops by two different administration modes with different fr equencies and intervals of application. At the beginning of cataract e xtraction (0.5-3 h after the last drop), 50-100 mu l aqueous fluid was aspirated from the anterior chamber and immediately stored at -80 deg rees C. Antibiotic concentrations were measured using high-performance liquid chromatography. Results: Generally, topical ofloxacin and cipr ofloxacin yielded aqueous humour levels higher than topical norfloxaci n. The highest concentrations of all tested fluoroquinolones were meas ured after using an application mode, in which one drop was given ever y 15 will be tween 0600 hours and 0800 hours, prior to operation. When applied by this mode, ciprofloxacin achieved a mean aqueous level of 0.380 (+/-0.328) mu g.ml(-1) (range 0.033-1.388 mu g.ml(-1)), norfloxa cin 0.182(0.118) mu g.ml(-1) (range 0.038-0.480 mu g.ml(-1)) and oflox acin 0.564 (0.372) mu g.ml(-1) (range 0.064-1.455 mu g.ml(-1)). These mean concentrations were above the minimum inhibitory concentration (M IC90), concentrations required for inhibition of 90% of pathogen strai ns in vitro of gramnegative bacteria, such as Proteus mirabilis and Es cherichia coli. Therapeutic values above the MIC90 of Staphylococcus e pidermidis, the pathogen causing eye infections most frequently, were reached by 67.5% of patients after ofloxacin and by 41% after ciproflo xacin, but never after norfloxacin treatment. Conclusion: Of the curre ntly available topical fluoro-quinolones. ofloxacin achieved the highe st aqueous humour concentration. This fluoroquinolone may be an useful ophthalmic agent for topical antibacterial management, but it does no t seem to be prophylactically effective against Streptococcus pneumoni ae or Pseudomonas aeruginosa.