Adapalene

Cumulative Irritation Potential of Adapalene 0.1% Cream and Gel Compared with Tretinoin Microsphere 0.04% and 0.1%

Dosik JS, MD, et al. Cutis. 2005;75(4):238-243.

Summary

The authors present an investigator-blinded, single-center, intra individual comparison study to determine the cumulative irritation potential of adapalene 0.1% cream and gel compared to tretinoin microsphere 0.04% and 0.1%. White petrolatum was used as a control. Thirty-one subjects were enrolled after excluding those with a history of inflammatory dermatoses such as psoriasis, eczema, or atopic dermatitis, and any individuals with a known allergy to ingredients in the study products. Patients underwent daily weekday application of the 5 study products under occlusive dressings, randomized to 52 X 2 centimeter zones on the upper back for 3 weeks. The study products were left on for a designated time period, removed and assessed for skin reactions, and then reapplied. In total, patients had 4 24-hour interval applications and 1 72-hour interval application per week, as the occlusive dressings were left on during the weekend. Test sites were scored for erythema on a scale from 0 (none) to 3 (severe). A product was discontinued if an erythema score of 3 was noted. In addition, primary lesions such as papules, vesicles, weeping, or pustules were also assessed. The investigator was blinded as to which product was applied to the different zones and assessment took place every day for 3 weeks except for weekends. If irritation occurred secondary to the adhesive used for the dressing, all applications were discontinued. At the end of the treatment period, a cumulative irritancy index was recorded for each patient. This index was calculated as the sum of erythema scoring and the number of readings. After performing a statistical analysis, both white petrolatum and adapalene cream and gel were found to be less irritating than the tretinoin formulations with p values of less than or equal to 0.01 and 0.05, respectively. Eight patients using tretinoin microsphere 0.1% and 9 patients using tretinoin microsphere 0.04% discontinued treatment, all secondary to irritation reactions.

Comment

The study is based on the 21-day cumulative irritancy assay and was done to assess the irritancy potential of adapalene versus new formulations of tretinoin. This study was supported by a research grant from Galderma R & D who make adapalene. The author also receives research grants from Galderma R & D. There was a statistically significant difference in irritancy potential when comparing tretinoin products to white petrolatum and to adapalene products. Discontinuation of study products occurred only in those areas treated with tretinoin microsphere 0.04% and 0.01%. While this study demonstrates adapalene has less potential to cause irritation compared to tretinoin, no conclusions regarding efficacy of the drugs can be drawn from this study. In patients with sensitive skin, adapalene may be the best choice of treatment. However, irritation from tretinoin may be reduced by less frequent dosing. Comparison studies are needed to evaluate both efficacy and adverse events of the different drugs and their formulations.

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