Drug delivery is one of the fastest growing areas in the pharmaceutical industry, with leading firms actively developing alternatives to injections. Options such as oral, topical, pulmonary (inhaler type), nanotechnology enabled, and transdermal drug delivery systems are all current research areas. Transdermal methods, which feature noninvasive delivery of medication through the patient’s skin, overcome the skin’s protective barrier in one of two ways: passive absorption or active penetration.

The transdermal patch is one of the most common methods of passive drug delivery. Applied to a patient’s skin, it safely and comfortably delivers a defined dose of medication over a controlled period of time. The drug is absorbed through the skin into the bloodstream. The nicotine patch is a prime example, but other common uses include motion sickness, hormone replacement therapy, and birth control. Passive delivery has two major disadvantages: the speed of drug absorption is dependent on the skin impedance, and only a limited number of drugs are capable of diffusing through the skin’s protective barrier at acceptable rates. As a result, major investment has been undertaken on active methods of transdermal drug delivery. Active methods include using ultrasonic energy to speed up drug diffusion, using RF energy to create microchannels through the stratum corneum (outer layer of the epidermis), and iontophoresis.