Skin protection: New barrier cream protects without irritating

Las Vegas - A skin barrier protection cream (Tetrix, Coria Laboratories) appears to reduce exposure to skin allergens and irritants and decrease symptoms of eczematous dermatitis, according to James Q. Del Rosso, D.O., dermatology residency director, Valley Hospital Medical Center, Las Vegas.

"Nonsteroidal options for long-term treatment of chronic-recurrent eczematous dermatoses involving the hands, including irritant contact dermatitis, allergic contact dermatitis and atopic dermatitis, are limited," Dr. Del Rosso tells Dermatology Times.

Therefore, he adds, dermatologists should welcome a nonsteroidal topical option that can relieve symptoms such as itching and burning and also provide some skin barrier protection activity.At the beginning of 2009, the Food and Drug Administration (FDA) approved Tetrix, a water-impermeable, aluminum magnesium hydroxide stearate (AMHS)-based cream that contains several silicate derivatives (dimethicone, cetyl dimethicone and cyclomethicone) formulated as an aqueous emulsion.

"The AMHS-based cream differs from other prescription barrier repair creams because its mechanism of action involves mainly providing barrier protection against sensitization and/or irritancy induced by external substances," Dr. Del Rosso says.

In contrast, previously approved prescription skin barrier creams work principally by repairing the epidermal barrier through moisturization and replacement of skin lipids, he explains. "Both approaches are important; that is, both protection and repair," he adds.

Studies

In a cumulative irritation study, researchers evaluated the AMHS-based cream in normal, healthy adults (age 18 to 65 years) under occlusive and semi-occlusive patches applied once daily on the upper back. The study lasted 21 days and evaluated comparator products in a similar fashion. Each day, investigators removed patches approximately 24 hours after application and evaluated the condition of each subject's skin, using a point system to calculate cumulative irritation scores.

Dr. Del Rosso says that, ultimately, the AMHS-based cream achieved a "mild" rating, posting lower scores than a negative control (mineral oil, Johnson's Baby Oil).

Although the AMHS-based cream isn't designed specifically for use under occlusion, Dr. Del Rosso notes that in this test, "Occlusive patch testing showed evidence of only slight potential for very mild cumulative irritation."

This is important because it supports that the AMH-based cream can be applied even if patients wear gloves during employment or activities, he says.

Another investigator-blinded study evaluated whether or not the AMHS-based cream would impede resolution of allergic contact dermatitis. This study included 12 subjects who were known to be nickel sensitive.

As part of the study, researchers induced allergic contact dermatitis in 10 of the subjects by occluding nickel sulfate under a Finn chamber for 48 hours at two sites on the volar forearm.

Investigators then used a four-point scale to evaluate local skin reactions including erythema, induration, edema, flaking and weeping.

After researchers removed the occlusive patches, the study cream was applied to a single site on each subject twice daily for 10 days, with results evaluated on treated and untreated sites at days four, seven, nine and 11.

Based on mean reaction scores for each test site at every visit and for all study parameters, the AMHS-based cream did not impede healing of the allergic skin reaction induced by nickel sulfate, Dr. Del Rosso says.

From days four through 11, he adds, test sites that received twice-daily application of the AMHS-based cream achieved lower scores for erythema, induration and edema.

"This suggests that the AMHS-based cream may provide some benefit in reducing the symptoms of cutaneous allergic reaction compared to untreated skin," Dr. Del Rosso says.

Somewhat similarly, an open-label study compared subject assessment of itching and burning due to allergic or irritant contact dermatitis on sites treated with the AMHS-based cream twice daily for two weeks versus untreated sites.

In this study, patients used a visual analog scale wherein zero meant no symptoms and 100 meant "worst possible" symptoms.

Subject assessment scores showed that applying the study cream decreased burning and itching at each of six follow-up visits.

Additionally, improvements in hand dermatitis symptoms on hands treated with the AMHS-based cream reached statistical significance from day four or five through to the study's end (p = 0.0185).

Stinging

A study involving 40 patients who experienced stinging when lactic acid 10 percent solution was applied to their nasolabial folds allowed researchers to evaluate both the cream's ability to protect against external irritants and the duration of this protection.

In this study, the AMHS-based cream produced a mean decrease in the severity of discomfort after application of lactic acid (lactic acid stinging test).

Over the first few hours after application of the AMHS-based cream, Dr. Del Rosso says, "The protective effect against lactic acid stinging and burning appeared to increase," lasting at least six hours.

Substantivity

Additionally, a bilateral, randomized, double-blind study compared the substantivity after hand washing of the AMHS-based cream to that of a commonly used over-the-counter (OTC) skincare preparation formulation (Vaseline Intensive Care, Unilever). Investigators mixed the test products with a fixed concentration of a pigmented cosmetic foundation that would not penetrate the skin.

At 15 minutes after applying a premeasured amount to randomized subjects' hands, a blinded technician washed subjects' hands using a defined procedure and designated cleanser. After washing, there was virtually none of the OTC care product left, while the AMHS-based cream provided protection against removal by water exposure during hand washing, Dr. Del Rosso says.

Allergen protection

Finally, a single-center, investigator-blinded, controlled trial has shown that the AMHS-based cream appears to provide barrier protection against nickel sulfate, neomycin and fragrance allergens.

For each of 35 evaluable subjects, investigators marked four pairs of test sites on the upper back and applied the AMHS-based cream to one test site in each of the four pairs. After the cream dried, investigators applied allergens to which subjects were known to be sensitive.

Overall, a smaller percentage of subjects exhibited positive reactions at the sites where the AMHS-based cream was applied before the allergen, compared to the sites where investigators applied the allergens alone.

At 24 hours, for example, differences between the test sites were statistically significant, with positive reactions noted in 28.6 percent of sites pretreated with the study cream versus 57.1 percent with the allergen alone (p = 0 .0455).

In clinical practice, Dr. Del Rosso says, "Patients would apply the AMHS-based cream two or three times daily so they could experience enhanced benefits," compared to the study patients who had the cream applied only once. DT

Disclosures: Data for all these studies are on file with Coria Laboratories, which sponsored the studies. Dr. Del Rosso is a researcher, consultant and/or speaker for Allergan, Coria, Galderma, Graceway, Intendis, Medicis, Onset Therapeutics, OrthoNeutrogena, Pharmaderm, Quinnova, Ranbaxy, SkinMedica, Stiefel, Unilever and Warner Chilcott.