EFFECTIVENESS OF CIPROFLOXACIN-POLYSTYRENE SULFONATE (PSS), CIPROFLOXACIN AND OFLOXACIN IN A STAPHYLOCOCCUS-KERATITIS MODEL

Purpose. Staphylococcus aureus causes several corneal infections that often result in corneal scarring and blindness. Presently, therapy oft en involves the use of fluoroquinolone antibiotic. This study, employi ng an experimental rabbit model of Staphylococcus keratitis, compared the effectiveness of two commonly prescribed formulation of fluoroquin olones of an experimental formulation, ciprofloxacin with polystyrene sulfonate (ciprofloxacin-PSS). The ciprofloxacin-PSS formulation uses an ion exchange resin to aid in the delivery of drug to the cornea. Me thods. Early (4-9 h postinfection, PI) and late (10-15 h PI) therapies were studied, employing 5 groups: ciprofloxacin-PSS, ciprofloxacin, o floxacin, PSS vehicle, and untreated. Dosing regimens were: every 30 m in, 60 min, or a single drop applied at 9 h PI. Eyes were observed by slit lamp examination (SLE) and bacterial colony forming units (CFU) p er cornea were determined. Results. Early phase therapy with ciproflox acin-PSS, ciprofloxacin, or ofloxacin administered every 30 ro 60 min were equally effective (P greater than or equal to 0.2880), decreasing CFU per cornea by > 5 log. Ciprofloxacin was significantly more activ e than ciprofloxacin-PSS or ofloxacin (P less than or equal to 0.0410) when applied as a single drop. Late therapy with ciprofloxacin-PSS, c iprofloxacin, or ofloxacin administered every 30 to 60 min resulted in > 3 log decrease in CFU per cornea relative to controls (P less than or equal to 0.0001). Conclusions. Topical treatment of experimental St aphylococcus keratitis with ciprofloxacin-PSS, ciprofloxacin, or oflox acin was effective. The effectiveness of ciprofloxacin-PSS suggests th at improved drug delivery systems employing an ion exchange resin coul d be useful in an ocular fluoroquinolone formulation.