By Carla Scaramella – Commercial Assistant

The terms topical and transdermal are sometimes confused. The fact that, by definition, all medications applied onto the skin are topical -that is, applied to the skin surface- may lead to such misconception. However, the term topical product involves the application of a drug on the skin to produce local effects at the site of application, avoiding systemic effects. Therefore, it is designed to minimally penetrate the skin layer.

Topical products are presented in many pharmaceutical forms. The most commonly used are the semisolid dosage forms, which include creams, gels, plasters, ointments and lotions.

Alternatively, transdermal products refer to pharmaceutical compounds that are applied on the skin, but cross the outermost layer of it -the skin barrier- for targeting an effect on more distant tissues or organs.

Such products require a special technology to control drug release and permeation through the skin barrier, in order to achieve a sustained dosage into the systemic circulation. According to the therapeutic needs and drugs’ properties, the delivery duration of a Therapeutic Transdermal System may range between 12 hours and 7 days.

Which are the advantages of a transdermal patch?

Enhances patient compliance with treatment in several ways:

• Non-invasive, pain free, self application, improving the administration of well-known molecules.
• Avoidance of frequent dosing administration, providing a controlled and sustained drug release for defined time periods -involving a lower peak plasma concentration compared to oral forms-.
• Reduction of side effects through avoiding both the gastrointestinal tract -minimizing local irritative GI effects- and the first-pass metabolism -safer in hepato-compromised patients-.
• Versatility for special patient populationts, as it can be administered to a patient who is sleeping, unresponsive, or unable to swallow oral medications.

How are transdermal patches used?

The body location for the patch application may vary with the therapeutic category of each drug, such as chest, buttocks or abdomen, upper torso or upper outer arm. The site of application should be clean, not oily, hairless; and the skin should be intact (unbroken).