Hydrocortisone acetate/urea

HYDROCORTISONE ACETATE/UREA (Carmol HC cream 1 % hydrocortisone acetate and 10% urea)... 

Hydrocortisone acetate/urea is a corticosteroid combination. Hydrocortisone depresses formation, release, and activity of endogenous mediators of inflammation as well as modifying the body s immune response. Urea has hydrating and keratolytic properties. They are indicated in the relief of inflammatory and pruritic manifestations of corticosteroid-responsive dermatoses. 

However, not all studies support the belief that urea is an effective penetration promoter.25,58-61 For instance, the latency time to induce erythema was not changed by three-weeks treatment with a moisturizer containing 5% urea62 or by pre-treatment of forearm skin with an aqueous solution of 10% urea.59 Moreover, urea (10%) had a minimal effect on the penetration of hydrocortisone through excised human and guinea pig skin.58 Hydrocortisone acetate was even retarded through hairless mouse skin with increasing concentrations of urea (up to 12%).25... 

For a good therapeutic effect the choice of the active substance and the choice of the vehicle are important. Physical and chemical factors play an important role. The solubility of the active substance in the vehicle and the concentration, the size of the molecule of the active substance, the partition between vehicle and skin, the particle size (in case of suspensions) and the nature of the vehicle (aqueous or lipid) determine the penetration speed and depth. Hydrocortisone, for example, is more lipid soluble in the ester form (hydrocortisone acetate). The latter will penetrate into the skin faster and more complete. Hydrocarbons, such as soft and liquid paraffin, release lipophilic active substances only very slowly and substances formulated in these bases will penetrate only in limited amounts into the skin. Fatty oils (vegetable oils, triglycerides) are able to pass into the upper layers of the skin. Penetration enhancers (salicylic acid, dimethyl sulfoxide, propylene glycol, urea) increase the penetration of active substances into the skin. 

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