Tretinoin gel microsphere less irritating than adapalene

National report - A small study has shown that facial skin tolerates treatment with tretinoin gel microsphere (TGM) technology better than treatment with the new 0.3 percent formulation of adapalene gel, a study co-author says.

Johnson & Johnson Consumer Companies often performs studies to compare the irritation potential of its products to that of competitors, says Marge Nighland, B.S., medical affairs, Johnson & Johnson Consumer and Personal Products Worldwide, Skillman, N.J., and a study co-author.

"The goal is mainly to let prescribing physicians know where we stand with regard to our irritation potential," she says. That’s because products that reduce irritation without sacrificing efficacy achieve better patient compliance, she notes.

TGM technology uses a drug-delivery system designed to slowly and selectively release the active ingredient to its site of action in hair follicles, Ms. Nighland says. To compare the irritation potential of TGM 0.04 percent with adapalene gel 0.3 percent, which researchers chose because a recent study showed it has greater efficacy in facial acne than 0.1 percent adapalene gel, researchers enrolled 27 female subjects aged 18 to 40. These subjects' facial skin had no irritation, acne, rashes or rosacea prior to the study's start, and no history of sensitive skin.

Researchers instructed all patients to apply TGM 0.04 percent to a randomly selected half of their faces and adapalene gel 0.3 percent to the other half once daily for two weeks. On weekdays, a technician supervised the product application. Subjects used one pump of the manufacturer-supplied TGM pump to lightly cover their faces with this medication. For adapalene gel 0.3 percent, subjects applied a half-pea sized amount of product with their fingers.

On each weekday, a blinded investigator assessed dryness and erythema using a scale on which zero meant none and eight meant severe scaling/fissuring or deep erythema. Subjects also evaluated their own itching and burning/stinging on weekdays, using a four-point scale (zero= none, one= mild, two= moderate, three= severe). Researchers also collected weekly chromameter skin surface erythema measurements for all subjects.

Twenty-five subjects (average age: 27.3 ± 7.5 years) completed the study. One subject discontinued treatment due to discomfort on the adapalene-treated side of her face on day seven. A second subject withdrew because of burning/stinging and itching on both sides of her face at day 11.

Regarding erythema, TGM was associated with significantly lower cumulative erythema scores than adapalene gel beginning on treatment day nine, Ms. Nighland tells Dermatology Times. At this point, TGM’s cumulative erythema score was approximately 12, versus about 38 for adapalene. Differences between the two treatments’ cumulative erythema scores were statistically significant at day 10 (TGM: 15; adapalene: 45) and day 15 (TGM: 15, adapalene: 52).

Chromameter-measured mean erythema values tended to be slightly higher on the adapalene side on days seven and 14, but these differences were not statistically significant.

Regarding TGM, Ms. Nighland notes that sorbic acid in its formulation can cause vasodilation in the absence of irritation. This pharmacological effect might have accounted for some of the chromameter-measured erythema associated with TGM, she says.

As for dryness, TGM posted significantly lower investigator-assigned scores for dryness/peeling from day six through the study's end. On day six, these scores were approximately 10 for TGM versus approximately 25 for adapalene. By day 15, the gap had grown to approximately 90 points (TGM: 40, adapalene: 130).

Similarly, Ms. Nighland says cumulative patient-assigned burning/stinging scores were significantly lower with TGM than with adapalene on day 10 (10 versus 30, respectively). But she reports no statistically significant differences between the treatments' cumulative scores for self-reported itching, which was a less common subject complaint than burning/stinging.

Overall, she says, "Subjects tolerated treatment with TGM 0.04 percent significantly better than treatment with adapalene gel 0.3 percent." During the last week of the study, investigators observed significantly less investigator-assessed erythema and dryness and subject-assessed stinging/burning, she adds. DT

Disclosure: This study was sponsored by Johnson & Johnson Consumer and Personal Products Worldwide.

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