Effect of low frequency ultrasound on the in vitro percutaneous absorption of clobetasol 17-propionate.

The effect of low frequency ultrasound (20 kHz) on the permeation of clobetasol 17-propionate (CP) through skin (sonophoresis) was studied. The ultrasound was applied at either continuous or discontinuous modes and at different intensities. The results showed that low frequency ultrasound significantly enhanced the permeability of CP across hairless mouse skin in vitro. Delivering the same amount of ultrasonic energy in different modes of application markedly influenced the flux and skin residual of CP. The on/off discontinuous ultrasound had greater enhancement on CP permeation than the continuous ultrasound. The results of skin histopathology and permeation experiment using various membranes demonstrate that both disordering of stratum corneum and convective flow resulted from the cavitation effect were responsible for sonophoretic enhancement of CP. The permeation of CP through hair follicles and sweat ducts was susceptible to the application of ultrasound.