TTS are drug delivery systems that can be applied to the human skin to release a variety of active substances. TTS enable substances to be absorbed by the skin, whereupon they enter the tissue beneath and into the bloodstream. The substance enters the bloodstream directly without having to be digested.
With an area of about two square meters, the skin is the largest organ in the human body, and it is also where around one third of all our blood circulates. The primary function of the skin is to protect the body from foreign objects and microorganisms. It also helps the body to retain moisture, yet it is not completely impermeable. Relatively small drug molecules can penetrate the skin, and this is how transdermal patches work.
In contrast to drugs taken orally, such as tablets and capsules, TTS have the advantage that the substance does not have to be digested first. This means that the substance remains chemically unchanged and directly accesses the part of the body where it needs to take effect via the bloodstream. As a result, this also avoids filtration and initial metabolism by the liver, or the ‘first-pass effect’. Another advantage of LTS patches is that they release the substance constantly and continuously over a long period of time. This means that the patient no longer has to take tablets several times a day. Forgetting to take a tablet or pill, such as for contraceptive purposes, for example, is also a thing of the past. Or pain relief substances can take a continuous effect, including during the night, if so prescribed by a doctor.
There are two different types of patch: the reservoir or membrane patch, which has a separate layer of the drug solution and a special membrane responsible for releasing the substance into the body via the skin, and the matrix patch, where the substance is embedded in an adhesive mass (matrix). This type of patch consists of a single layer, which acts as an adhesive film, layer of active substance and release liner at the same time.