Disadvantages Of Epidermis

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1. Epidermis: The multilayered envelope of the epidermis varies in thickness, depending on the cell size and number of cell layers, which ranges from 0.8mm on palms and soles down to 0.06mm on the eyelids. It further consists of two layers: a) Stratum corneum: It is the outermost layer of the skin and also termed as horny layer. It is approx 10mm thick when in dry conditions but swells to several times the thickness when fully hydrated. It is flexible but relatively impermeable and known as the principal barrier for penetration. It constitutes of 75 to 80% proteins, 5 to 15% lipids and 5 to 10% ondansteron material on the dry weight basis. b) Viable epidermis- Situated beneath the stratum corneum and varies in thickness from 0.06mm on the eyelids…show more content…
Dermis: Dermis is composed of a matrix of a connective tissue which contains lymphs, blood vessels and nerves and is about 3 to 5mm thick layer. On one hand it provides nutrients and oxygen to the skin and on other hand it removes toxins and waste products too. The blood supply thus keeps dermal concentration of permeation very low, and the resulting concentration difference across the epidermis provides the vital driving force for transdermal permeation. 3. Subcutaneous connective tissue: The subcutaneous fat tissue or hypodermis supports the dermis and epidermis. This layer serves as fat storage area, and helps to regulate temperature and provides nutritional support too. For transdermal drug delivery drug has to penetrate through all the three layers of the skin and reach into systemic circulation while in case of topical drug delivery, only penetration through stratum corneum is important and then retention of drug in skin layers is…show more content…
Single-layer Drug-in-Adhesive The adhesive layer of this system also contains the drug. In this type of patch the adhesive layer not only serves to adhere the various layers together, along with the entire system to the skin, but is also responsible for the releasing of the drug. The adhesive layer is surrounded by a temporary liner and a backing. 2. Multi-layer Drug-in-Adhesive The multi-layer drug-in adhesive patch is similar to the single-layer system in that both adhesive layers are also responsible for the releasing of the drug. The multi-layer system is different however that it adds another layer of drug-in-adhesive, usually separated by a membrane (but not in all cases). This patch also has a temporary liner-layer and a permanent backing. 3. Reservoir Unlike the Single-layer and Multi-layer Drug-in adhesive systems the reservoir transdermal system has a separate drug layer. The drug layer is a liquid compartment containing a drug solution or suspension separated by the adhesive layer. This patch is also backed by the backing layer. In this type of system the rate of release is zero order. 4.

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