Transdermal patch

Transdermal Patch

A typical transdermal patch.

A transdermal patch is a medicated adhesive patch designed to deliver a specific dose of medication through the skin and into the bloodstream. By bypassing the digestive system, these patches offer a controlled release of the medication, often resulting in more consistent blood levels of the drug compared to oral administration.

History

Transdermal patches were first introduced in the late 1970s and have since evolved, incorporating advanced technology and materials to improve efficiency and patient compliance.

Mechanism of Action

The primary advantage of transdermal patches lies in their ability to provide a steady release of medication. The patch's structure typically consists of:

• An adhesive layer that secures the patch to the skin.
• A reservoir or matrix containing the medication.
• A rate-controlling membrane that dictates the speed at which the drug is delivered.

Upon application, the medication diffuses from the patch, passing through the outermost layer of skin (the stratum corneum) and entering the bloodstream.

Types of Transdermal Patches

There are several different types of patches based on their design and drug delivery mechanism:

• Reservoir patches: Contains a reservoir of the drug, separated by a rate-controlling membrane.
• Matrix patches: Drug is embedded within the adhesive matrix.
• Drug-in-adhesive patches: The drug is incorporated directly into the adhesive.
• Multi-layer patches: Multiple layers, which may contain separate drugs or act as rate-controlling mechanisms.

Advantages and Disadvantages

Advantages

• Steady and prolonged release of medication.
• Reduced side effects compared to oral administration.
• Improved patient compliance due to convenience and reduced dosing frequency.
• Bypasses the digestive system, reducing potential for gastrointestinal irritation.

Disadvantages

• May cause skin irritation at the application site.
• Limited to drugs that can penetrate the skin in effective amounts.
• Potential for misuse or overdose if multiple patches are applied.

Common Uses

Transdermal patches have been developed for a variety of medications, including:

• Nicotine (for smoking cessation)
• Fentanyl (for pain management)
• Estrogen and progesterone (for hormone replacement therapy)

See Also

• Drug delivery systems
• Topical medication
• Pharmacokinetics

References

• Prausnitz, M. R., & Langer, R. (2008). Transdermal drug delivery. Nature Biotechnology, 26(11), 1261-1268.
• US FDA: Transdermal Patch