Metrogel (Metronidazole) Drug Information: Clinical Pharmacology

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May 27, 2012

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Rosacea »

Rosacea facts

Rosacea is a common, chronic, incurable, adult acne-like skin condition.
Rosacea has periodic ups and downs (flares and remissions).
Rosacea symptoms tend to come and go.
Rosacea is easily controllable and medically manageable.
Rosacea may begin with easy facial blushing or flushing.
Rosacea commonly affects the central third of the face, especially the nose.
Rosacea causes tiny red pimples and fine red lines on the facial skin.
Rosacea may be mistaken for rosy cheeks, sunburn, or quite often, acne.
Rosacea triggers include alcohol, hot or spicy foods, emotional stress, and heat.
Rosacea can be a very bothersome and embarrassing condition.
Rosacea untreated can cause a bulbous red nose (like W.C. Fields).
Prompt recognition and proper treatment permit pe...

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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.