Transdermal patches are adhesive patches placed on the skin to deliver medication directly into the bloodstream. They are designed to release a controlled amount of medication over time, providing a steady dose without the need for injections or oral medications. Common uses include pain relief, hormone replacement, and smoking cessation. These patches are made of several layers, including a drug reservoir, a permeable membrane, and an adhesive layer. The medication penetrates the skin and enters the bloodstream, allowing for effective treatment with fewer side effects compared to traditional methods. Examples of medications delivered via patches include nicotine and fentanyl.