Unrest, sleep disorders, nausea – the list of side effects associated with many medicinal products is long. Consequently, patients often refuse to take their medication which causes frustration and stress for caregivers and relatives as well as the patients themselves, and jeopardizes the therapeutic outcome. Many active substances do not necessarily have to be taken orally. Instead, they can be transported into the bloodstream via the skin using so-called transdermal therapeutic systems – with multiple benefits in terms of patient therapy.
The origin of transdermal patches can be traced back to the 1960s’ space travel. The astronauts required an anti-emetic product to combat travel sickness. A tablet to be taken with water was obviously impractical because of the spacesuits worn by the astronauts. The problem was resolved by attaching a small patch to the skin behind the astronauts’ ear which delivered the anti-emetic active substance directly into the bloodstream through the skin. The well known nicotine patch was the next major milestone for transdermal patches approximately 20 years ago.
Today, there are approximately 20 plus active substances with a transdermal mode of action available. These are already used in a wide range of medical indications. Sometimes even in cases where tablets are not effective, as evidenced with the active substance, Rotigotine, for the management of Parkinson’s disease. This drug displays poor bioavailability when administered via the oral route with tablets. Bioavailability refers to the amount of active substance that is available in the bloodstream. For Rotigotine the challenge is that it does not pass the obstacles posed by the human digestive system inhibiting its availability. However, with a transdermal patch, the active substance is delivered directly into the bloodstream through the skin and has considerable better bioavailability in the human body.
This characteristic is undoubtedly one of the major advantages of patch therapy. Conventional tablets always have to pass through the gastrointestinal tract, as a result of which all too often only part of the active substance actually reaches the target site. Furthermore, depending on the area of application, the patch is effective for a few hours up to one week, thereby improving patient comfort. Furthermore, active substance levels in the human body can be maintained at more constant levels over a longer period. Positive illustrative examples concern the treatment of Alzheimer’s disease, Parkinson’s disease as well as in pain relief. Since plasma levels do not fluctuate and there is no metabolisation in the liver as in case of oral administration, there are often fewer side effects. If nevertheless unexpected adverse reactions do occur, treatment can be discontinued at any time simply by removing the patch. The dosage can be adjusted easily by applying different patch sizes.
These key benefits put forward a highly convincing argument for patients and caregivers alike. A recent patient survey carried out on behalf of LTS AG, a leading distributor of transdermal therapeutic systems, shows that 84% of patch users interviewed allocated a score of eight to ten (10 = very pleasant experience, one very unpleasant experience). No scores between 1 and 3 were allocated. When asked which features were the most impressive, patients mostly commented on efficiency and efficacy, improved quality of life, fewer side effects and ease of use.
TRANSDERMAL SYSTEMS – THE VERSATILE OPTION
Transdermal patches are an interesting alternative for many therapeutic indications. The actual system used always depends on the active substance and therapy required, and is therefore tailored to suit individual needs.
CURRENT THERAPEUTIC INDICATIONS:
Dr. Schlange, why aren’t transdermal patches used more often?
Of the approximately 2,500 active substances available in pharmacies today, only ca. 20 are being administered via transdermal systems to date. Not every pharmaceutically active substance can penetrate the skin barrier which is designed to protect the body.
And the ones that can – in contraception for instance?
Tablets are mass-produced in entirely different, much larger quantities. In a direct cost comparison, transdermal systems cannot compete, despite their effective, yet gentle mode of action. For the example of contraception, the cost disadvantage may mean that, unfortunately, patients cannot or do not want to pay higher cost.
However, in other indication the use is very intensive.
Yes, since patches are a viable and comfortable treatment option especially in chronic deseases such as Alzheimer’s disease, Parkinson’s disease or pain relief, e.g. in palliative medicine. Patches are similar to an intravenous infusion, but do not restrict patients mobility. This improves patients’ quality of life during treatment.
And in the cases where the skin barrier cannot be overcome ?
In some circumstances the skin barrier can be overcome nevertheless. For example a transdermal system recently authorized by the USA FDA for migraine contains an active substance that normally does not transfer the skin. I.e. as the normal active substance, a salt cannot be administered via the transdermal route. When applying a special technique that the active substance can now be transported through the skin into the bloodstream when applying a gentle electrical current.
Dr. Tim Schlange
Member of the LTS AG Board