Transdermal

Overview

File:Applying transdermal patch.jpg

Application of a transdermal patch

Transdermal drug delivery is a method of administering medications through the skin. This route of administration allows for the drug to be absorbed directly into the bloodstream, bypassing the digestive system. Transdermal systems are often used for drugs that require steady, controlled release over time.

Mechanism of Action

Transdermal drug delivery works by allowing the active ingredient to pass through the stratum corneum, the outermost layer of the skin, and into the deeper layers where it can enter the bloodstream. The drug is typically contained in a patch that adheres to the skin, and it diffuses through the skin layers by passive diffusion.

Advantages

Transdermal delivery offers several advantages over other routes of administration:

• Avoidance of the gastrointestinal tract: This reduces the risk of gastrointestinal side effects and drug degradation by stomach acids.
• Controlled release: Transdermal patches can provide a steady release of medication over time, which can improve therapeutic outcomes and reduce dosing frequency.
• Improved patient compliance: Patches are easy to apply and remove, which can enhance adherence to treatment regimens.

Limitations

Despite its advantages, transdermal drug delivery has some limitations:

• Skin irritation: Some patients may experience irritation or allergic reactions at the site of application.
• Limited drug types: Only drugs that are potent and have suitable molecular size and lipophilicity can be effectively delivered transdermally.
• Variable absorption: Factors such as skin condition, age, and site of application can affect drug absorption rates.

Common Applications

Transdermal patches are used for a variety of medications, including:

• Nicotine patches: Used to aid in smoking cessation by providing a controlled release of nicotine.
• Hormone replacement therapy: Patches can deliver hormones such as estrogen and testosterone.
• Pain management: Fentanyl patches are used for chronic pain management.
• Cardiovascular drugs: Nitroglycerin patches are used for angina pectoris.

Related Pages

• Drug delivery system
• Pharmacokinetics
• Skin absorption
• Patch (pharmacy)