Keratolytic effect

Older Compounds. Some antimycotics have been used for a long time Whitfield s ointment is a typical example (1907). The ointment usually contains 6% ben2oic acid [65-85-0] and 3% sahcyhc acid [69-72-7] C H O. The action is attributed to the keratolytic effect of the sahcyhc acid... 

Salicylic acid is used to treat acne, warts, dandruff, psoriasis, and similar conditions. In the treatment of acne, it slows the shedding of skin cells in hair follicles, so they do not clog the pores and cause pimples. It also has a keratolytic effect—it causes dead skin cells to slough off— which removes the top layer of skin and clears existing pore clogs. 

Salicylic acid (ortho hydroxybenzoic add) is a beta hydroxy acid agent. It is a lipophilic compound which produces desquamation of the stratum corneum via removal of intercellular lipids [3] (see salicylic acid section). Given its keratolytic effects, it has become an increasingly popular superficial peeling agent. Salicylic acid peels induce injury via thinning or removal of the stratum corneum. In addition, salicylic acid potentially enhances the penetration of TCA. 

Salicylic acid has a keratolytic effect, thus eliminating superficial pigmented keratinocytes and stimulating cells turnover. This superficial peeling allows TCA to act a low concentration to remove pigmented keratinocytes through papillary dermis (see Fig. 14.12). 

Huber C, Christophers E (1977) Keratolytic effect of salicylic acid. Arch Dermatol Res 257 293-297... 

Salicylic acid is one of the most commonly used keratolytics. It causes a disruption in corneocyte-to-corneocyte cohesion in the abnormal horny layer of psoriatic skin. This serves to remove scales, smooth the skin, and decrease hyperkeratosis. The keratolytic effect enhances penetration and... 

Dithranol in combination with urea is widely used in psoriasis to improve the clinical efficacy, to minimize the dithranol concentration, to achieve the desired effect, to shorten the contact, to get a better hydration of the stratum corneum, and to decrease the proliferation rate of the keratinocytes. Gabard and Bieli showed an increased keratolytical effect of salicylic acid by adding 10% urea.54 Hagemann and Proksch55 showed in 10 patients with psoriasis under a 2-week treatment with a 10% urea ointment increased stratum corneum hydration, a small decrease in TEWL, a reduction in epidermal thickness (-29%), and a decreased epidermal proliferation (-51%). The altered expression of involucrin and cytokeratins as marker for epidermal proliferation was partially reversed.55... 

Nook, T.H., In vivo measurement of the keratolytic effect of salicylic acid in three ointment formulations. Br. J. Dermatol., 1987, 117 243-5. 

Gabard, B. and E. Bieli, Salicylic acid and urea — possible modification of the keratolytic effect of salicylic acid by urea. Hautarzt, 1989, 40 (Suppl. 9) 71-3. 

Table 19.2). In seven patients with severe ichthyosis a pronounced keratolytic effect was noticed and the skin became soft and pliable after treatment with high concentrations (about 10%).17 After treatment with 10% urea (Calmuril ) the number of stratum corneum cell layers was reduced in 6 of 11 patients with ichthyosis.28... 

Loden, M., Bostrom, P., and Kneczke, M., Distribution and keratolytic effect of salicylic acid and urea in human skin, Skin Pharmacol., 8, 173, 1995. 

Whitfield s ointment, used for Trichophyton rubrum, has a keratolytic effect, and local irritation can occur (SED-12, 685) (35). 

At concentrations above 2% salicylic acid has a keratolytic effect, causing the keratin layer of the skin to shed. Keratolysis is achieved by increasing the hydration of the stratum corneum, softening the cells and facilitating dissolution of the intracellular cement that bonds the cells together so that they separate and detach (desquamate). Moisture is essential to this process and is provided by either the water in the formulation or the occlusive effect produced by its application to the skin. 

It exerts its keratolytic effect by increasing the hydration of epithelial cells. 

The keratolytic effect of salicylic acid enhances penetration and efficacy of some other topical agents such as corticosteroids. ... 

LHA up to 10% is widely used in Europe. A derivative of salicylic acid (SA) with an additional fatty chain, its lipophilicity is increased. Even with a lowered concentration, its keratolytic effect is three times more potent than SA. It possesses a superficial desquamating effect and it increases the ration of cycling keratinocytes as part of an overall boosting of epidermal turnover [11, 93]. 

A dramatic ( 75%) reduction in size and number of desmosomes was observed in a freeze-fracture analysis of keratinocyte membranes in patients with psoriasis treated with etretinate (Kitajima and Mori, 1983). This reduction in desmosomal size and number (Williams and Elias, 1981), which was particularly evident in the stratum comeum but also observed in the stratum spinosum of both lesional and nonlesional skin, appeared to be of sufficient magnitude to contribute significantly to the keratolytic effect of retinoids in hyperkeratotic disorders. Other factors, for example, decreased tonofrlaments and decreased glycocalyx cohesion, may also be contributory. This effect also has been observed in vitro as retinoids cause increased shedding of squames from stratified cultures of human foreskin epidermal cells (McGuire et al., 1982 Kubilus, 1980). 

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