Sonophoresis thermal

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. ... 

Various ultrasound intensities in the range of 0.1-2W/cm have been used for sonophoresis. In most cases, use of higher ultrasound intensities is limited by thermal effects. Several investigations have been performed to assess the dependence of sonophoretic enhancement on ultrasound intensity. Miyazaki, Mizuoka, and Takada. foimd a relationship between the plasma concentrations of indomethacin transported across the hairless rat skin by sonophoresis (therapeutic conditions) and the ultrasoimd intensity used for this purpose. Specifically, the plasma indomethacin concentration at the end of three hours after sonophoresis (0.25 W/cm ) was about 3-fold higher than controls at the same time. However, increasing intensity by 3-fold (to 0.75 W/cm ) further increased sonophoretic enhancement only by 33%. Mortimer, Trollope, and Roy found that application of ultrasoimd at IW/cm increased transdermal oxygen transport by 40%i while that at 1.5 W/cm and 2 W/cm induced an enhancement by 50%i and 55 /o, respectively. 

Ultrasound can be applied either in a continuous or a pulsed mode. A pulsed mode of ultrasound application is used many times because it reduces the severity of adverse side effects of ultrasound, such as thermal effects. However, pulsed application of ultrasound may have a significant effect on the efficacy of sonophoresis. As will be discussed later, cavitational effects, which play a crucial role in sonophoresis,... 

---