Because of its usefulness in treating facial
rosacea,
metronidazole may also be an effective treatment for
ocular rosacea. The toxicity of
metronidazole on the corneal epithelium has not previously been reported. In this study, the effects of
metronidazole on rabbit corneal epithelium in vitro were evaluated. Epithelial cell cultures were exposed to various concentrations of
metronidazole to determine its effect on cell morphology, viability, and wound healing. Both morphological changes and cell loss were seen after 1 day of incubation in media containing
metronidazole at concentrations of > or = 3.0 mg/ml. In media with
metronidazole at 1.0 mg/ml, these toxic effects were not seen. The effects of
metronidazole on wound healing were determined by comparing the area of
wounds in the epithelial cell layer for time periods of up to 44 h. There was no statistically significant delay in
wound closure when cells were incubated in media containing
metronidazole at a concentration of 2.0 mg/ml as compared with cultures incubated in media without
metronidazole. However, a significant delay in
wound closure occurred at concentrations of > or = 3.0 mg/ml. The results at these
drug concentrations suggest that
metronidazole has low corneal epithelial toxicity. Allowing for the dilutional effects of tears in patients with normal tear function, concentrations of 4.0-5.0 mg/ml (0.4-0.5%) would probably be tolerated by the corneal epithelium. Clinical safety and efficacy studies are necessary to determine if topical
metronidazole will prove useful for the treatment of
ocular rosacea.