Skin absorption pathway

The skin absorption pathway refers to the mechanisms by which substances applied to the skin surface penetrate the stratum corneum and are transported into the viable epidermis, dermis, and potentially systemic circulation. Absorption depends on both drug properties (size, lipophilicity, solubility), anatomical skin site, integrity/hydration of the stratum corneum, and the presence of appendages such as hair follicles and sebaceous/sweat glands. The main mechanisms are: - Passive diffusion: Most common, driven by concentration gradient, especially for small, lipophilic molecules. - Active transport: Rare, requires carrier proteins and energy expenditure, more relevant for certain polar and large molecules. - Appendageal/Transappendageal route: Utilizes hair follicles and glands, important for large and polar compounds, also serves as reservoirs. - Transcellular and Intercellular penetration: Drug molecules can move through cells (transcellular, especially hydrophobic compounds) or between cells (intercellular, mostly lipophilic molecules). The rate and extent of skin absorption are limited primarily by the properties of the outer stratum corneum and can be enhanced by increasing skin hydration or disrupting the barrier. The pathway is fundamental to transdermal drug delivery and also constitutes a route of unintentional exposure to toxic substances. Unlike specific targets such as receptors or enzymes, the skin absorption pathway is a physical route, not a molecular or protein entity.

Other names

Percutaneous absorption pathwayDermal absorption routeTransdermal absorption pathway

Not applicable (drugs leverage this pathway for systemic or local delivery, mechanisms include passive diffusion, active transport, and appendageal penetration)