Transdermal delivery drug influence

Cutaneous biotransformation is mostly associated with the stratum basale layer where there can be phase I and phase II metabolism. However, the skin is not very efficient, compared to the liver. The epidermal layer accounts for the major portion of biochemical transformations in skin, although the total skin activity is low (2-6% that of the liver). Where activity is based on epidermis alone, that layer is as active as the liver or, in the case of certain toxicants, several times more active. For some chemicals, metabolism can influence absorption, and transdermal delivery systems of drugs utilize this activity. For example prodrug such as lipid esters are applied topically, and cutaneous esterases liberate the free drug. These basal cells and extracellular esterases have been shown to be involved in detoxification of several pesticides and bioactivation of carcinogens such as benzo(a)pyrene. For rapidly penetrating substances, metabolism by the skin is not presently considered to be of major significance, but skin may have an important first-pass metabolic function, especially for compounds that are absorbed slowly. 

Behl CG, Bellantone NH, Flyim GL. Influence of age on percutaneous absorption of drug substance. In Kyodoineus AF, Berner B, eds. Transdermal Delivery of Drugs. Boca Raton, EL CRC Press, 1998 109-132. 

Excipients can influence delivery from topical and transdermal medications. The propensity of the drug to migrate from the formulation to the application surface is affected by factors such as lipophilicity of the vehicle, drug solubility in the formulation, and effects of additives on the barrier properties of the skin or mucosal surface. 

Although differences in surface characteristics, such as smoothness and the presence of hair, might be expected to influence TDB from transdermal dose forms, there are limited supportive data. Evidence suggests that differences in sebum sheet thickness between different sites may contribute to differences in the delivery of drugs to the It is also reasonable... 

Sintov, A.C. andBotner, S. (2006) Transdermal drug delivery using microemulsion and aqueous systems Influence of skin storage conditions on the in vitro permeability of diclofenac from aqueous vehicle systems. Int. J. Pharm., 311, 55-62. 

Moreover, polymeric nanoparticles can also be used for transdermal drug delivery, especially thanks to their small size (100 nm-1 p) enabling skin penetration. Interaction of nanoparticles with skin is strongly influenced by their physicochemical properties such as size, surface charge, polymer used, drug-loading efficacy and the manner of application [16]. 

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