Cumulative irritation potential of metronidazole gel compared to azelaic acid gel after repeated applications to healthy skin.

Author(s): Ziel K, Yelverton CB, Balkrishnan R, Feldman SR

Affiliation(s): Center for Dermatology Research, Department of Dermatology, Wake Forest, Winston-Salem, NC, USA.

Publication date & source: 2005-11, J Drugs Dermatol., 4(6):727-31.

Publication type: Clinical Trial; Randomized Controlled Trial

BACKGROUND: Metronidazole 0.75% gel and azelaic acid 15% gel are commonly used to treat rosacea. Irritation is a common side effect. OBJECTIVE: To assess the cumulative irritation potential of metronidazole 0.75% gel and azelaic acid 15% gel. METHODS: Metronidazole 0.75% gel, azelaic acid 15% gel, and a white petrolatum negative control were applied under occlusive conditions to the upper back of a total of 33 healthy subjects. There were twelve 24-hour applications (4 times a week) and three 72-hour applications on weekends during a 3-week period. Skin reactions (erythema score +/- other local reaction) were assessed within 15 to 30 minutes of removal of the products. RESULTS: The mean cumulative irritancy index of metronidazole 0.75% gel was significantly lower than that of azelaic acid 15% gel and not significantly higher than the negative control product. There was increasing cumulative irritancy with azelaic acid; no cumulative irritancy was seen for either metronidazole or white petrolatum. CONCLUSION: Metronidazole 0.75% gel is less irritating in sustained use than azelaic acid 15% gel.