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


CONCLUSIONS
Metronidazole 0.75% gel is less irritating in sustained use than azelaic acid 15% gel.
Ziel
Kristin
K
Center for Dermatology Research, Department of Dermatology, Wake Forest, Winston-Salem, NC, USA.
Yelverton
Christopher B
CB
Balkrishnan
Rajesh
R
Feldman
Steven R
SR
D000279:Administration, Cutaneous; D000328:Adult; D000368:Aged; D003879:Dermatologic Agents / Q000008:administration & dosage / Q000009:adverse effects*; D003998:Dicarboxylic Acids / Q000008:administration & dosage / Q000009:adverse effects*; D004334:Drug Administration Schedule; D004890:Erythema / Q000139:chemically induced*; D005260:Female; D005782:Gels; D006801:Humans; D007509:Irritants / Q000009:adverse effects; D008297:Male; D008795:Metronidazole / Q000008:administration & dosage / Q000009:adverse effects*; D008875:Middle Aged; D010577:Petrolatum / Q000008:administration & dosage; D012867:Skin / Q000187:drug effects*; D023422:Skin Irritancy Tests / Q000379:methods; D013997:Time Factors
D003879:Dermatologic Agents; D003998:Dicarboxylic Acids; D005782:Gels; D007509:Irritants; D008795:Metronidazole; D010577:Petrolatum; C010038:azelaic acid