Metrogel

CLINICAL PHARMACOLOGY

Mechanism of Action

The mechanism of action of metronidazole in the treatment of rosacea is unknown.

Pharmacodynamics

The pharmacodynamics of metronidazole in association with the treatment of rosacea are unknown.

Pharmacokinetics

Topical administration of a one gram dose of METROGEL (metronidazole) to the face of 13 patients with moderate to severe rosacea once daily for 7 days resulted in a mean ± SD Cmax of metronidazole of 32 ± 9 ng/mL. The mean ± SD AUC(0-24) was 595 ± 154 ng*hr/mL. The mean Cmax and AUC(0-24) are less than 1% of the value reported for a single 250 mg oral dose of metronidazole. The time to maximum plasma concentration (Tmax) was 6-10 hours after topical application.

Clinical Studies

In a randomized, vehicle-controlled trial, 746 subjects with rosacea were treated with metronidazole gel, 1% or gel vehicle once daily for 10 weeks. Most subjects had “moderate” rosacea at baseline. Efficacy was determined by recording reduction in inflammatory lesion counts and success rate in the Investigator Global Assessment (percentage of subjects “clear” and “almost clear” of rosacea at the end of the study). The scale is based on the following definitions:

Table 3: Investigator Global Assessment Scale

Score Grade Definition
0 Clear No signs or symptoms present; at most, mild erythema
1 Almost Clear Very mild erythema present. Very few small papules/pustules
2 Mild Mild erythema. Several small papules/pustules
3 Moderate Moderate erythema. Several small or large papules/pustules, and up to 2 nodules
4 Severe Severe erythema. Numerous small and/or large papules/pustules, up to several nodules

The results are shown in the following table:

Table 4: Inflammatory Lesion Counts and Global Scores in a Clinical Trial of Rosacea

  Metronidazole Gel, 1% Vehicle
N Results N (%) N Results N (%)
Inflammatory lesions 557   189  
Baseline, mean count   18.3   18.4
Week-10, mean count   8.9   12.8
Reduction   9.4 (50.7)   5.6 (32.6)
Investigator Global Assessment 557   189  
Subject clear or almost clear   214 (38.42)   52 (27.51)
Subject with no change   159 (28.5)   77 (40.7)

Subjects treated with metronidazole gel, 1% experienced a mean reduction of 9.4 inflammatory lesions in the Week-10 LOCF group, compared to a reduction of 5.6 for those treated with vehicle, or a difference in means of 3.8 lesions.

The contribution to efficacy of individual components of the vehicle has not been established.

Last reviewed on RxList: 3/29/2010
This monograph has been modified to include the generic and brand name in many instances.

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