Sonophoresis mechanisms

Sonophoresis is defined as the transport of drugs through intact skin under the influence of an ultrasound. Ultrasound at various frequencies in the range of 20 kHz to 16 MHz has been used to enhance skin permeability [1-3]. This chapter attempts to present sonophoresis, experimental variables, possible mechanisms of action, and clinical applications. 

Ultrasound (or sonophoresis) is a technology more traditionally associated with the fields of physiotherapy, sports medicine, and medical imaging rather than transdermal dmg delivery. Compared to physiotherapy, where high-frequency energy (1 MHz) is used, in transdermal dmg delivery low-frequency energy (20 kHz region) is applied across the skin. Cavitation, the acoustically induced formation and oscillation of gas bubbles formed because of the mechanical energy supplied, is the most probable... 

The use of ultrasound (US) to enhance percutaneous absorption (so-called sonophoresis or phonophoresis) has been studied over many years, and is the basis of US propagation and US effects on tissue, and the use of US in transdermal delivery have been reviewed in detail. The proposed mechanisms by which US enhances skin penetration include cavitation, thermal effects and mechanical perturbation of the SC that is, US acts on the barrier function of the membrane. ... 

In conclusion, despite the exciting low-frequency US results obtained, there remain important questions about mechanism, local skin effects and tolerability, reversibility, and ultimate practicability. These issues must be addressed before sonophoresis can move from research to development mode. 

In order to understand the mechanisms of sonophoresis, it is important to identify various effects of ultrasound exposure on the human tissue since one or more of these effects may contribute to the mechanism of sonophoresis. A brief description of the various biological effects of ultrasound is provided below. 

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