Mechanism of Action of Accelerants on Skin Penetration

Abstract

SUMMARY.— The ability of a number of liquids to increase the permeability of human skin in vitro has been assessed in terms of their power to accelerate the percutaneous penetration of tri‐n‐propyl phosphate (TPP). The most effective “accelerants”. 8 M‐urea and dimethylsulphoxide (DMSO), increased the permeability of full thickness skin to TPP up to 190 times, they were also amongst those compounds, which produced the greatest reduction in skin impedance and the most swelling of the stratum corneum, suggesting that part of their effectiveness may be due to an ability to lower the diffusional resistance of the stratum corneum. The acceleratns were all able to extract soluble components from the stratum corneum; DMSO extracted lipoprotein, and chloroform‐methanol extracted phospholipids, suggesting the possibility of ultrastructural modifications consistent with an increase in permeability. For a liquid to be a good accelerant it must also release the penetrant readily to the aquesous milieu of the viable epidermis. This process could be hindered by an excessively unfavourable partition coefficient or by the extremely low water solubility of a penetrant.

Nickel Susceptibility and Skin Barrier Function to Water after Treatment with a Urea-Containing Moisturizer

“…Several studies in normal skin have shown that urea is an effi cient accelerant for the penetration of different substances ( table 1 ) [21][22][23][24][25][26] . However, not all studies support the belief that urea is an effective penetration promoter [27][28][29][30][31] .…”

Therapy of Resistant Psoriasis with Topical Corticosteroids and Dimethylsulfoxide

“…The actual presence of the solvent in the skin appears essential. Enhancement of penetration could not be detected 3 h or more after pretreatment of skin with DMSO [8], It has been postulated that the solvent swells the corneum, thereby lowering its dififusional resistance [3], Equally penetrating homologues of DMSO, however, do not produce corneal swelling [11], DMSO can also leach out lipoproteins, suggesting that it somehow alters the structural integ rity of the corneum barrier [1], DMSO rapidly penetrates human skin. 25-40% of a topically applied dose is absorbed within 30 min [16].…”

Allantoin in Treatment of Psoriasis

“…Sw a n beck [1968], however, admits that in psoriasis the dominat ing effect of urea treatment is softness of the skin, making it necessary to add steroids to the cream in order to get good clinical results. Acceleration of skin penetration by urea in high concentrations [Allenby et al, 1969] could be of more importance, especially in combined prescriptions which contain both urea and an active anti-psoriatic such as tar or steroids. In that way one could theoretically expect results from an allantoin preparation like Alphosyl.…”