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

Journal of Drugs in Dermatology, Nov-Dec, 2005 by Kristin Ziel, Christopher B. Yelverton, Rajesh Balkrishnan, Steven R. Feldman

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Address for Correspondence

Steven R. Feldman MD PhD

Department of Dermatology

Wake Forest University School of Medicine

Medical Center Boulevard

Winston-Salem, NC 27157-1071

Phone: 336-716-7740

Fax: 336-716-7732

e-mail: sfeldman@wfubmc.edu

Kristin Ziel MS IV, (a) Christopher B. Yelverton MD MBA, (a) Rajesh Balkrishnan PhD, (b) Steven R. Feldman MD PhD (a)

a. Center for Dermatology Research, Department of Dermatology, Wake Forest, Winston-Salem, NC

b. University School of Medicine, Winston-Salem, NC; Division of Pharmacy Practice and Administration, The Ohio State University, Columbus, OH

Table 1. Erythema Scale.

0    No reaction              No erythema
0.5  Erythema barely visible
1    Mild erythema            Slight pinkness present
2    Moderate erythema        Definite redness easily recognized
3    Severe erythema          Intense redness

Table 2. Documentation of Local Reactions.

O   Oedema
P   Papules                Many small, red, solid elevations; surface of
                           reaction has granular feeling
V   Vesiculation           Small (<0.5cm) circumscribed elevations
                           having translucent surfaces so that fluid is
                           visible
B   Blisters               Bullae; large (>0.5cm) circumscribed
                           elevations with visible fluid
Pu  Pustules               Small inflammatory elevations containing
                           yellow-white exudate
H   Hyperpigmentation      An increase of the usual pigmentation limited
                           to the test area
W   Weeping/oozing         May be a sign of vesiculation or blisters
                           (epidermal damage) and manifested as crusting
S   Spreading of reaction  That is, a reaction where no product came
    beyond test area       into contact with the skin
    evaluated

Table 3. Mean Cumulative Irritancy Index by Study Product.

                           MCII (SD)        Differences
Study Product                               B        C

A Metronidazole 0.75% gel  0.0182 (0.0426)  -1.034*  -0.0071
B Azelaic acid 15% gel     1.0525 (0.5231)            1.0273*
C White petrolatum         0.0253 (0.0571)

*Significant at [alpha] = 0.01.