The efficacy of topical ciprofloxacin and norfloxacin in the treatment of experimental Pseudomonas keratitis

Cornea. 1991 Jan;10(1):25-8.


An aminoglycoside-resistant strain of Pseudomonas aeruginosa was injected intrastromally into the corneas of rabbits, and keratitis was allowed to develop over a 22-h period. Rabbits were treated with either 0.75% ciprofloxacin, 1% norfloxacin, or 1.36% tobramycin administered topically every 15 min for 1 h and then every 30 min for the following 3 h. All therapy ceased 26 h postinoculation. Rabbits were killed 1 h after the treatment, and the number of bacteria per cornea were quantified in terms of bacterial colony-forming units. Aqueous humor specimens were obtained from rabbits receiving norfloxacin and ciprofloxacin, and bioassays were performed to determine drug concentration. Ciprofloxacin caused a 5 log reduction in the number of bacterial colony-forming units, as compared with untreated controls (p less than 0.0001); it also produced a significantly greater reduction in bacterial colony-forming units than either norfloxacin or fortified tobramycin drops (p less than 0.0001). Norfloxacin produced a 2 log reduction in bacterial colony-forming units, as compared with untreated controls (p less than 0.0001). The mean aqueous concentration of norfloxacin (7.5 micrograms/ml) was substantially less than that achieved by ciprofloxacin (30.5 micrograms/ml). We conclude that ciprofloxacin may be a useful broad spectrum, topical chemotherapeutic agent in the therapy of aminoglycoside-resistant P. aeruginosa keratitis.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Administration, Topical
  • Animals
  • Ciprofloxacin / administration & dosage
  • Ciprofloxacin / therapeutic use*
  • Colony Count, Microbial
  • Keratitis / drug therapy*
  • Keratitis / microbiology
  • Norfloxacin / administration & dosage
  • Norfloxacin / therapeutic use*
  • Pseudomonas Infections / drug therapy*
  • Pseudomonas aeruginosa / drug effects
  • Pseudomonas aeruginosa / growth & development
  • Rabbits
  • Tobramycin / administration & dosage
  • Tobramycin / therapeutic use


  • Ciprofloxacin
  • Norfloxacin
  • Tobramycin