The potential of intact skin as the route of drug administration has been known for years; the inspiration for using skin for the delivery of drug is obtained from ancient times. Utilization of skin as a route for delivering drugs as has been an alternative to conventional methods including injections and tablets. Advantages of transdermal drug delivery include the avoidance of pain, hepatic first-pass metabolism, sustain drug release, easy use and withdrawal in case of side effects. However, the major limitation for transdermal drugdelivery system (TDDS) is that the skin has the outmost layer of the epidermis; the stratum corneum (SC) provides an outstanding barrier towards the absorption of substances. Oral delivery of complex molecules such as peptides and proteins has been hampered by the degradation in the gastrointestinal tract.
As a result, various types of particulate systems such as biodegradable microspheres andliposomes have been proposed as potential delivery vehicles to protect these drugs in the gastrointestinal tract. Unfortunately, these particulates generally display low oral absorption efficiencies. Millions of unsafe injections are delivered in developing countries, and the transmission of certain blood borne pathogens via this route is thought to be a major public health problem. Several technological advances developed to overcome this challenge. These advances can be broadly divided into two categories; physical and chemical methods. Physical methods employed for increasing transport of molecules across the skin uses mechanical, electrical, magnetic or thermal energy source to promote transport of macromolecules by disrupting the skin membrane. Examples of physical approaches include the use of micro needle array, ballistic liquid jet, high velocity particles, ultrasound, electric current, abrasion, ablation, lasers, pressure waves, radiofrequency thermal ablation, magnetophoresis of diamagnetic solutes and thermophoresis.
To overcome the barrier properties of the skin for drugs is an incorporation of suitable vehicles. Substances that promote the penetration of topically applied drugs through stratum corneum and epidermis are commonly referred to as skin permeation enhancers, accelerants, adjuvant, or sorption promoters. Dimethylsulfoxide (DMSO) is widely studied penetration enhancers in many areas of pharmaceutical sciences as a “universal solvent”.