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2005 OMIG, Abstract 15

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A Comparison of Ocular Penetration and Microbiological Efficacy of Fourth Generation Fluoroquinolones in Cataract Surgery Patients

Terrence P. O'Brien1 and David W. Stroman2

1.The Wilmer Eye Institute, Johns Hopkins University, Baltimore, MD; 2.Alcon Research Ltd., Fort Worth, TX

Purpose: To correlate the ocular penetration and the microbiological activity of the fluoroquinolones moxifloxacin 0.5% ophthalmic solution (Vigamox®, Alcon Laboratories, Inc.) and gatifloxacin 0.3% solution (Zymar®, Allergan, Inc.) following topical administration prior to routine cataract surgery.

Methods: The penetration study was a prospective, randomized, double masked, clinical study involving 50 patients (moxifloxacin 0.5% n = 25, gatifloxacin 0.3% n = 25) undergoing routine cataract extraction at the Wilmer Eye Institute. Patients were administered one drop of antibiotic every ten minutes for four doses beginning one hour prior to surgery. Samples of aqueous humor were obtained via paracentesis at the time of the incision antibiotic concentrations were determined using standardized high performance liquid chromatography (HPLC) procedures. Comparative in vitro activity testing was performed on a recent clinical Staphylococcus aureus ocular isolate. Standard disk diffusion and broth dilution testing methods were used as recommended by CLSI (formerly NCCLS). Disk diffusion testing was performed by applying 80 ul of moxifloxacin -1.8 ug/ml and gatifloxacin - 0.48 ug/ml to a 13 mm disk.

Results: Aqueous humor concentrations for moxifloxacin were 1.80 ( ± 1.21) ug/ml while those achieved with gatifloxacin were 0.48 ( ± 0.34) ug/ml. This 3.8-fold concentration difference was statistically significant (P= 0.00003). MIC determinations revealed a moxifloxacin MIC of 0.06 ug/ml compared with 0.13 ug/ml for gatifloxacin. The disks soaked with moxifloxacin resulted in a 24 mm zone of inhibition whereas gatifloxacin demonstrated no activity against the test organism of S. aureus.

Conclusions: Moxifloxacin demonstrated greater penetration into the aqueous humor than gatifloxacin. This difference in concentration resulted in a marked differentiation in observed microbiological activity between moxifloxacin and gatifloxacin that may have clinical relevance in the prevention of Staphylococcus infections post-cataract surgery. Supported by Alcon Laboratories, Inc.

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