Formulation, in vitro release and transdermal diffusion of azelaic acid with topical niacinamide / J.M. Moolman
Moolman, Judith Margaretha
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Acne is a common skin disease that affects the follicular unit of the skin. Inflammatory- and noninflammatory forms of acne exist. The most affected areas on the body include the face, upper part of the chest and the back. These are the areas with the most sebaceous follicles. Acne occurs when hyperkeratinisation causes the cells of the hair follicle to shed too fast. These cells then block the follicle opening. Thus, sebum cannot pass through the hair follicle onto the skin. The human skin is composed of three layers, namely the epidermis, which acts as a waterproof layer and a barrier to infections; the dermis, which contains the skin appendages; and the subcutaneous fat layer. Skin acts as a protective layer against pathogens and damage to the body. It also provides a semi-impermeable barrier to prevent water loss. Azelaic acid and niacinamide are both currently used in the treatment of acne. Azelaic acid is a saturated dicarboxylic acid which is used to treat mild to moderate acne. It has antibacterial, keratolytic and comedolytic properties. Niacinamide, on the other hand, is the amide of nicotinic acid and is beneficial in the treatment of both papular and pustular acne. It has a demonstrated anti-inflammatory action and causes dose-dependent inhibition of sebocyte secretions. The Pheroid™ delivery system is a colloidal system that consists of even lipid-based submicron-and micron-sized structures that are very unique in nature. This technology is able to improve the absorption and/or efficacy of various active ingredients, as well as other compounds. In this study, a cream, Pheroid™ cream, a gel and a Pheroid™ gel were formulated, containing both azelaic acid and niacinamide. Stability tests were conducted on these formulations for six months, and it was established that none of the formulations were stable under the different storage conditions. Tests that were conducted during stability testing, as determined by the Medicines Control Council, included: assay, mass variation, appearance, viscosity, pH determination and confocal laser scanning microscopy (CLSM). Diffusion studies (12 hours long in total) with vertical Franz cells were conducted with Caucasian female skin obtained after abdominoplastic surgery. Tape-stripping followed in order to establish the epidermis and dermis concentrations of azelaic acid and niacinamide. Significant concentrations of both active ingredients were found in the epidermis and the dermis after 12 hours.
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