Topical application of the
antibacterial agent metronidazole is effective in the treatment of moderate to severe
rosacea, although its mechanism of action has yet to be clearly established.
Metronidazole preparations (0.75 and 1% cream, 0.75% gel and 0.75% lotion) were significantly more effective than placebo in patients with moderate to severe
rosacea when administered to the affected area once or twice daily for 7 to 12 weeks. The mean number of papules and pustules decreased by between 48 and 65.1% during the treatment period. Reductions were fairly consistent regardless of formulation, strength or application frequency and were significant compared with placebo (p < 0.05). In 1 study, most of the overall effects of
metronidazole were observed within the first 3 weeks. Although data are limited, topical
metronidazole appears to improve inflammatory lesions and
erythema as effectively as oral
tetracyclines. Like
tetracyclines, however,
metronidazole has no effect on
telangiectasia.
Metronidazole 0.75% gel seems to be effective in maintaining remission of
rosacea symptoms in patients successfully treated with both oral
tetracycline and topical
metronidazole. In the only study, 77% of patients treated with
metronidazole gel compared with 58% of placebo recipients (p < 0.05) remained in remission 6 months after the
tetracycline was stopped. The effects of topical
metronidazole preparations on
rosacea symptoms are palliative, not curative, but preliminary data suggest that relapse rates after cessation of
therapy are no worse than those after cessation of oral
oxytetracycline. Topical
metronidazole formulations are generally well tolerated locally, with stinging, dryness, burning and
itching reported in < or = 2% of patients. Because minimal concentrations of
metronidazole are absorbed after
topical administration, systemic adverse events and drug interactions seen with oral or intravenous
metronidazole are unlikely.
CONCLUSIONS: Topical
metronidazole formulations are significantly more effective than placebo when used in the initial treatment of patients with moderate to severe
rosacea. Furthermore, limited evidence suggests that the use of topical
metronidazole alone may be as effective as oral
tetracyclines against the disorder's inflammatory component. Therefore, for those patients with a preference for topical rather than oral
therapy, the use of a topical
metronidazole formulation must be a consideration.