A skin patch, formally known as a transdermal patch, is a medicated adhesive device applied to the skin’s surface. It delivers medication or other substances through the skin directly into the bloodstream. This method allows for a steady release over an extended period, providing a continuous therapeutic effect. Unlike oral medications, skin patches bypass the digestive system, which can help avoid drug breakdown in the stomach or liver.
How Skin Patches Work
A transdermal patch allows medication to cross the skin’s protective layers. A typical patch consists of a backing layer, a drug reservoir or matrix, an adhesive layer, and often a membrane that controls the drug’s release rate. Before application, a temporary liner covers the adhesive and drug components, which is removed just before use.
Once applied, medication migrates from the patch into the skin. The outermost layer, the stratum corneum, acts as the primary barrier, composed of dead, flattened cells. For absorption, drug molecules must be small and lipid-soluble enough to penetrate this tough layer.
After permeating the stratum corneum, drug molecules continue through the epidermis and into the dermis. The dermis contains numerous capillaries. Here, the medication is absorbed into the systemic circulation. Many patches also incorporate permeation enhancers, which temporarily increase the skin’s permeability by gently disrupting its lipid structure.
Common Uses for Skin Patches
Transdermal patches are used for various medical conditions, offering a convenient alternative to oral medications or injections. Nicotine patches, for example, deliver a controlled amount of nicotine to help individuals reduce tobacco dependence during smoking cessation. This steady release helps manage withdrawal symptoms.
Hormonal patches are also common, including those for birth control and hormone replacement therapy. These patches provide a consistent dose of hormones, simplifying daily regimens. For motion sickness, scopolamine patches are often placed behind the ear to prevent nausea and vomiting, with a single patch potentially lasting up to three days.
Skin patches are also used in pain management. These include fentanyl patches for severe chronic pain, lidocaine patches for localized relief, and buprenorphine patches. Other applications include clonidine patches for high blood pressure and rivastigmine patches for Alzheimer’s disease.
Proper Application and Removal
Correct application and removal of skin patches are important to ensure both effectiveness and safety. Begin by selecting a clean, dry, and hairless area of skin, such as the upper arm, chest, or back, avoiding broken or irritated skin. After removing the protective liner, press the patch firmly onto the skin for about 20 to 30 seconds, ensuring all edges adhere securely. Rotating the application site with each new patch helps prevent skin irritation from prolonged exposure to the same area.
Should a patch fall off prematurely, replace it with a new one, following prescribed instructions. Avoid exposing the patch to external heat sources like heating pads or hot baths, as increased heat can cause rapid medication absorption. Always wash your hands thoroughly after handling any patch to prevent accidental exposure.
For removal, gently peel the patch from the skin. Many patches, particularly those containing potent medications like fentanyl, still retain active drug after use and require careful disposal to prevent accidental exposure. The FDA generally recommends folding the used patch in half, sticky sides together, and flushing it down the toilet immediately, though local regulations or take-back programs may offer alternative disposal methods. Skin reactions, such as redness, itching, or inflammation, can occur at the application site due to the patch’s adhesive or active ingredients. If a significant reaction occurs, consulting a healthcare professional is advisable.