Porous Resins as a Cavitation Enhancer for Low‐frequency Sonophoresis

The application of low‐frequency ultrasound enhances drug transport through the skin, a phenomenon referred to as low‐frequency sonophoresis. This enhancement is mediated through cavitation, the formation and collapse of gaseous bubbles. We hypothesized that the efficacy of low‐frequency sonophoresis can be significantly enhanced by provision of nuclei for cavitation. In this study, we used two porous resins, Diaion® HP20 and Diaion HP2MG (2MG), as cavitation nuclei. We measured the effect of these resins on cavitation using pitting of aluminum foil. 2MG showed a higher efficacy in enhancing cavitation compared with Diaion HP20. 2MG was also effective in enhancing transdermal mannitol transport. These results confirm that the addition of cavitation nuclei such as porous resins further increases the effect of low‐frequency ultrasound on skin permeability. © 2002 Wiley‐Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 91:753–759, 2002