Transdermal

Transdermal is a route of administration wherein active ingredients are delivered across the skin for systemic distribution. Examples include transdermal patches used for medicine delivery, and transdermal implants used for medical or aesthetic purposes.

Overview

A transdermal patch is adhered to the skin to deliver medication into the bloodstream. It is a viable alternative to oral administration because it helps to avoid the first pass metabolism. The rate of absorption is dependent on a number of factors, including the skin's physical condition and the presence of hair.

Mechanism of action

The skin is a complex barrier to direct drug penetration, therefore, transdermal patches are designed to control the rate of drug delivery into the systemic circulation. The drug penetrates through the skin layers and into the bloodstream. The drug's molecular size, ionization and lipid solubility determine its ability to penetrate the skin.

Advantages and disadvantages

Transdermal administration has several advantages over oral administration. It provides a controlled release of the medication into the patient, usually through a porous membrane covering a reservoir of medication. It eliminates the need for multiple daily doses, improving patient compliance. However, the main disadvantage is that the skin is a very effective barrier and only medications with very specific properties can be absorbed through the skin.

See also

• Pharmacokinetics
• Route of administration
• Drug delivery

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