In vitro phonophoresis of digoxin across hairless mice and human skin: Thermal effect of ultrasound

Abstract

The phonophoresis of digoxin was studied in vitro through human and hairless mouse skin. Sonication was carried out with continuous mode at an intensity of 1 and 3 W/cm 2 and a frequency of 3.3 MHz for 10 min. Sonication at 3W/cm 2 significantly increased the absorption of digoxin through mouse skin. Percutaneous penetration was not increased using an intensity of 1W/cm 2 under the same experimental conditions. Enhanced digoxin penetration at 3W/cm 2 can be explained by the mechanical and/or thermal action of ultrasound waves. Thermal simulation from electrical resistance increased digoxin flux in comparable amounts to those obtained by sonication at 3 W/cm 2. There was no enhancement of digoxin absorption across human skin by ultrasound, probably due to dermal retention of this lipophilic drug. Further studies will be necessary to determine the relative importance of the thermal effects of ultrasound on percutaneous administration of drugs.