title: Cumulative irritation potential of metronidazole gel compared to azelaic acid gel after repeated applications to healthy skin.
abstract: 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.
authors.affiliation: Center for Dermatology Research, Department of Dermatology, Wake Forest, Winston-Salem, NC, USA.
authors.forename: Kristin
authors.initials: K
authors.lastname: Ziel
authors.forename: Christopher B
authors.initials: CB
authors.lastname: Yelverton
authors.forename: Rajesh
authors.initials: R
authors.lastname: Balkrishnan
authors.forename: Steven R
authors.initials: SR
authors.lastname: Feldman
mesh_terms: 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
chemical_list: D003879:Dermatologic Agents; D003998:Dicarboxylic Acids; D005782:Gels; D007509:Irritants; D008795:Metronidazole; D010577:Petrolatum; C010038:azelaic acid