The Science of Drug Delivery within the Skin
What is skin?
Anatomically, the skin is made up of two primary tissue layers, an outer epidermis, and an underlying dermis, which together constitute the skin. The dermis itself contains two layers: the outermost layer is referred to as the papillary dermis while the deeper layer is known as the reticular dermis. The papillary dermis contains vast microcirculatory blood and lymphatic plexuses. Beneath the dermis is the subcutaneous tissue, which is composed of fatty and muscular tissue and an abundance of nerves.
There are three primary methods by which drugs may be injected: intramuscularly, subcutaneously and intradermally.
The intradermal injection method typically requires a standard needle to be carefully inserted into the dermis at an angle of 15 degrees, making it a precise and awkward procedure for the user. It has been the major challenge for patients or care-providers administering an intradermal injection and is why a syringe is best used to administer into the subcutaneous or intramuscular tissue.
By targeting the skin (intradermal), the drug delivery can take place anywhere on the body rather than in the usual five, often overused, sites of subcutaneous injection. This has proven to enhance the uptake, bio-availability and efficacy of drugs.