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Chicago—After topical administration, moxifloxacin 0.5% (Vigamox, Alcon Laboratories) penetrates better into the cornea than gatifloxacin 0.3% (Zymar, Allergan) to achieve significantly higher levels in the epithelium and stroma, reported Terry Kim, MD, at the annual meeting of the Ocular Microbiology and Immunology Group.
Dr. Kim presented the results of a controlled, randomized, open-label, multicenter clinical study measuring corneal epithelial and stromal concentrations achieved following instillation of moxifloxacin or gatifloxacin.
A total of 48 patients undergoing penetrating keratoplasty were enrolled at six participating centers. Co-investigators included Steven Dunn, MD, Detroit; Edward J. Holland, MD, Cincinnati; Harold R. Katz, MD, Baltimore; Stephen S. Lane, MD, St. Paul, MN; and Michael B. Raizman, MD, Boston.
However, the peak fluoroquinolone concentration achieved in the stroma was approximately three-fold higher for moxifloxacin compared with gatifloxacin (48.5 versus 15.7 µg/g) while moxiflox-acin achieved a peak level in the epithelium that was seven-fold higher than that measured for gatifloxacin (81.2 versus 12.3 µg/g), said Dr. Kim, associate professor of ophthalmology, Duke University School of Medicine, and associate director, cornea and refractive surgery, Duke University Eye Center, Durham, NC.
"Previous in vivo data from a rabbit model demonstrated that topically administered moxifloxacin offered superior penetration into the cornea as well as into the aqueous humor and vitreous compared with gatifloxacin," Dr. Kim explained. "This study corroborates those findings but provides the human data that are most relevant to clinicians."
Information was also presented comparing the ratio of the peak mean concentration maximum (Cmax) levels achieved by the two fluoroquinolones in the stroma against reported minimal inhibitory concentration (MIC) values for important endophthalmitis and keratitis pathogens including Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pneumoniae, and Mycobacterium fortuitum.
For moxifloxacin, the Cmax:MIC ratio for all four organisms exceeded 500 and ranged up to 970. The ratio of Cmax:MIC for gatifloxacin for the four pathogens ranged from < 100 to 175.
"These results provide refractive and cataract surgeons some reassurance that a fourth-generation fluoroquinolone administered shortly before a procedure will result in stromal concentrations able to inhibit the growth of important pathogens that can invade the cornea intraoperatively," Dr. Kim said.