Fluoroquinolone provides superior broad pathogen coverage

Fort Lauderdale, FL—The results from a clinical trial demonstrate that topical moxifloxacin 0.5% ophthalmic solution (Viga-mox, Alcon Laboratories) instilled in a q.i.d. dosing regimen achieves a significantly higher concentration in aqueous humor compared with topical gatifloxacin 0.3% ophthalmic solution (Zymar, Allergan) to provide antibacterial coverage for a broader range of important ocular pathogens, said Joel D. Aronowicz, MD, at the annual meeting of the Association for Research in Vision and Ophthalmology.

The study is a prospective, randomized, double-masked, clinical trial, conducted at the University of Texas Southwestern Medical Center, Dallas, where Dr. Aronowicz is a postdoctoral research fellow in the department of ophthalmology.

Data were presented from 46 patients who underwent planned phacoemulsification and IOL implantation. Each patient began fluoroquinolone treatment on the day before surgery with four times a day administration of moxifloxacin (n = 22) or gatifloxacin (n = 24). A fifth drop was instilled on the day of surgery, 1 hour prior to planned entry of the anterior chamber. Aqueous humor samples were obtained using a technique that avoided contamination from the ocular surface, and the fluoroquinolone concentrations were analyzed using HPLC.

"The results of this study show that the commercially available preparation of moxifloxacin penetrates into the aqueous humor with a clinically relevant dosing regimen to achieve therapeutically effective kill levels for most endophthalmitis-causing pathogens and to a statistically significantly higher level than gatifloxacin," Dr. Aronowicz said. "Our results are consistent with those of previous investigations of aqueous humor concentrations achieved with these fourth-generation fluoroquinolones.

"Taken together with data from safety studies showing no evidence of ocular surface toxicity with topical moxifloxacin treatment, we conclude that moxifloxacin offers safe and effective prophylaxis for surgery involving clear corneal incisions," he added.

Better coverage

The fourth-generation fluoroquinolones have been a welcome advance in meeting the need for antibiotics that would provide better coverage against important ocular pathogens, including atypical Mycobacteria, Streptococcus species, and resistant S aureus, are less susceptible to the development of bacterial resistance, and that can achieve greater penetration into the aqueous.

"Studies in the literature indicate that second- and third-generation fluoroquinolones can achieve therapeutic concentrations on the ocular surface and in the stroma, but not in the aqueous humor. Reported concentrations achieved with q.i.d. dosing of levofloxacin 0.5% (Quixin, Santen) and ciprofloxacin 0.3% (Ciloxan, Alcon Laboratories) are only 0.28 µg/ml and •0.15 µg /ml, respectively," Dr. Aronowicz said.

Previous studies have examined the potential for relative safety differences between gatifloxacin and moxifloxacin. In studies of healthy volunteers as well as in patients undergoing LASIK, there was no evidence of clinical toxicity associated with either agent. The safety of moxifloxacin was further confirmed in studies of patients undergoing LASEK and cataract surgery in which it was shown to have no adverse effects on postoperative corneal and conjunctival healing.