Transdermal

The stratum corneum is the top layer of the skin and varies in thickness from approximately ten to several hundred micrometres, depending on the region of the body.

[1] It is composed of layers of dead, flattened keratinocytes surrounded by a lipid matrix, which together act as a brick-and-mortar system that is difficult to penetrate.

This layer is about ten times as thick as the stratum corneum; however, diffusion is much faster here due to the greater degree of hydration in the living cells of the viable epidermis.

By this route, drugs cross the skin by directly passing through both the phospholipids membranes and the cytoplasm of the dead keratinocytes that constitute the stratum corneum.

[5][6][7] A third pathway to breach the Stratum Corneum layer is via tiny microchannels created by a medical micro-needling device of which there are many brands and variants.

[8] Investigations at the University of Marburg, Germany, using a standard Franz diffusion cell showed that this approach is efficient in enhancing skin penetration ability for lipophilic as well as hydrophilic compounds.

A transdermal patch which delivers medication is applied to the skin. The patch is labelled with the time and date of administration as well as the administrator's initials.