Transdermal drug delivery offers an attractive alternative to the conve ntional drug delivery methods of
oral administration and injection. However, the stratum corneum acts as a barrier that limits the penetration of
substances through the skin. Application of ultrasound to the skin increases its permeability (sonophoresis) and
enables the delivery of various substances into and through the skin.
Ultrasound has been used extensively for medical diagnostics and to a cer tain extent in medical therapy
(physiotherapy, ultrasonic surgery, and hyperthermia). Nevertheless, it has only recently become popular as a
technique to enhance drug release from drug delivery system s. A number of studies suggest the use of ultrasound
as an external mean of delivering drugs at increased rates and at desired times.
This chapter presents the main findings in the field of sonophoresis, namely transdermal drug delivery and
transdermal monitoring. Particular attention is paid to proposed enhancement mechanisms and future trends in the
field of cutaneous vaccination and gene delivery.
Keywords: Sonophoresis, phonophoresis, ultrasound, skin, physical enhancers, transdermal drug delivery.
