Conventional topical delivery systems.

Effective dermatologic therapy depends on both the active drug and the properties of the delivery system. A topical delivery system, or vehicle, is defined as the substance that carries a specific drug into contact with and through the skin. The challenge to topical drug delivery is the transport across the skin barrier. Depending on the delivery system, penetration of the active drug can be quite variable and this is largely due to the physiochemical properties of the constituent components of that vehicle. Selection of the appropriate drug delivery system will depend on the active, anatomic site of disease and patient preferences.