Sample<unk> es. On left is a 'reservoir' type, on the right a 'Single-layer Drug-in-Adhesive' version. Both contain exactly the same active ingredient with identical release rates. There are five main types of<unk> es. 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. It is characterized by the inclusion of the drug directly within the skin‐contacting adhesive placed onto the epidermis. Multi-layer Drug-in-Adhesive The multi-layer drug-in-adhesive patch is similar to the single-layer system; the multi-layer system is different, however, in that it adds another layer of drug-in-adhesive, usually separated by a membrane (but not in all cases). One of the layers is for immediate release of the drug and other layer is for control release of drug from the reservoir. This patch also has a temporary liner-layer and a permanent backing. The drug release from this depends on membrane permeability and diffusion of drug molecules. Reservoir Unlike the single-layer and multi-layer drug-in-adhesive systems, the reservoir<unk>  system has a separate drug layer. The drug layer is a liquid compartment containing a drug solution or suspension separated by the adhesive layer. The drug reservoir is totally encapsulated in a shallow compartment molded from a drug-impermeable metallic plastic laminate, with a rate-controlling membrane made of a polymer like vinyl acetate on one surface. This patch is also backed by the backing layer. In this type of system the rate of release is zero order. Matrix The matrix system has a drug layer of a semisolid matrix containing a drug solution or suspension. The adhesive layer in this patch surrounds the drug layer, partially overlaying it. Also known as a monolithic device. Vapour Patch In a vapour patch, the adhesive layer not only serves to adhere the various layers together but also to release vapour. Vapour patches release essential oils for up to 6 hours and are mainly used for decongestion. Other vapour patches on the market improve quality of sleep or aid in smoking cessation.
Transdermal patch
Transdermal spray
Injectable filler
Transdermal analgesic patch
Aqueous cream
Subcutaneous implant
Intradermal injection
Subcutaneous injection