Optimisation of a dosing regime for a topical skin protectant (barrier cream)

Context: Topical skin protectants (barrier creams) have the potential to reduce or enhance the severity of dermal lesions following exposure to allergens or irritants. Therefore, it is essential that such products are subject to appropriate clinical evaluation prior to marketing. Consequently, it is important to accurately define a dosing regime in order to assess test products under appropriate conditions. Objective: In this study, we extended the use of a standard rubefacient (methyl nicotinate; MN) assay to establish the optimum thickness and duration of action of a novel barrier cream (RD1433). White petroleum jelly (Vaseline®) was used as a comparator product. Methods: The dermal response to MN was measured on the volar forearm skin of volunteers (n = 12; average age 47.5 years) using an array of biophysical instruments and visual scoring. When applied at a nominal thickness of 0.1 mm, RD1433 retained effectiveness against MN for up to six hours. In contrast, Vaseline® was relatively ineffective. Moreover, RD1433 provoked no measurable signs of irritation and so can be considered acceptable for further clinical evaluation. Conclusion: Future clinical studies using RD1433 should be based on topical application of a 0.1 mm thickness layer every six hours.