Cumulative Irritation Comparison of Adapalene Gel and Solution With 2 Tazarotene Gels and 3 Tretinoin Formulations
Forty-two subjects with normal skin were enrolled in a single-center study to assess the cumulative irritancy potential of adapalene (Differin® gel 0.1% and Differin solution 0.1%) compared with tazarotene (Tazorac® gels 0.05% and 0.1%), tretinoin (Retin-A Micro® gel 0.1%, Avita® cream 0.025%, and Avita gel 0.025%), and white petrolatum (negative control). All test materials were applied randomly, under occlusion, to sites located on either side of the midline—the mid thoracic area of the subjects’ backs. All patches were applied daily, Monday through Friday, to the same sites, unless the degree of reaction to a test product or adhesive necessitated removal (grade 3). Thirty-eight of the 42 subjects (90.5%) completed the study. Thirty-four of those 38 subjects (89.5%) had to discontinue using both tazarotene concentrations due to intolerance. Patch discontinuations for the remaining test materials were as follows: 7 subjects discontinued use of tretinoin microsphere gel 0.1%, 3 discontinued tretinoin cream 0.025%, 1 discontinued tretinoin gel 0.025%, and 1 discontinued adapalene gel 0.1%. None of the subjects discontinued use of the white petrolatum or the adapalene solution 0.1%. Adapalene gel and solution 0.1% were statistically (P
| View this table | Table 2. Irritation Classification* |
results Of the 42 subjects enrolled, 38 subjects (90.5%) completed the study. Demographic data are presented in Table 3. Results are summarized in Table 4 and Figure 1. Figure 2 shows a clinical photograph of typical irritation observed during the study.
| View this table | Table 3. Demographic Data |
| View this table | Table 4. Summary of Mean Cumulative Irritancy Index (MCII) Statistical Comparisons |
In the study, the reasons for treatment discontinuation were not always due to an erythema score of 3 but also because of other clinical aspects of severe intolerance, such as epidermal peeling with subsequent superficial erosion (without severe erythema). Figure 3 shows the number of subjects who discontinued wearing the patches due to an irritation score of 3.
Adapalene gel and solution 0.1% were each significantly less irritating during sustained use than tazarotene gels 0.05% and 0.1%, tretinoin microsphere gel 0.1%, and tretinoin cream 0.025%. Although tretinoin gel 0.1% MCII was numerically superior to both adapalene gel and solution MCIIs, no statistically significant difference could be depicted between the 3 products. Repeated applications of adapalene gel or solution resulted in levels of irritation that were not significantly different from the white petrolatum control. back to top
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