About Time-Release Patches
There are currently 5 types of transdermal patches.
- 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.
- 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. One of the layers is for immediate release of the drug and other layer is for control release of drug from the reservoir. 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.
- 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.
- 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.
- Vapor Patch - In this type of patch the adhesive layer not only serves to adhere the various layers together but also to release vapor. The vapor patches are new on the market and they release essential oils for up to 6 hours. The vapor patches release essential oils and are used in cases of decongestion mainly. Other vapor patches on the market are controller vapor patches that improve the quality of sleep. Vapor patches that reduce the quantity of cigarettes that one smokes in a month are also available on the market.
Best Locations To Apply Patches – The best locations to apply patches are where there are large concentrations of small blood vessels under the top skin (dermal) layers. The following illustration should be used as a general guide:
Transdermal Patch Construction
- Liner - Protects the patch during storage. The liner is removed prior to use.
- Formula – Supplement or medication in direct contact with release liner
- Adhesive - Serves to adhere the components of the patch together along with adhering the patch to the skin
- Membrane - Controls the release of the medication or supplement from the reservoir and multi-layer patches
- Backing - Protects the patch from the outer environment