IN-VITRO PHONOPHORESIS OF MANNITOL, ESTRADIOL AND HYDROCORTISONE ACROSS HUMAN AND HAIRLESS MOUSE SKIN

Ultrasound is frequently used in physical medicine. In a preliminary s tudy, we demonstrated that the thermal effect of ultrasound was the pr incipal explanation for the increase in the diffusion rate of digoxin. The aim of this study was to investigate further the phonophoresis of three drugs with a cooling thermostat, thus suppressing the thermal e ffect of ultrasound. Sonication was carried out at 1.5 W/cm(2), 1.1 MH z for 20 min. We used modified Franz diffusion cells adapted for sonic ation. During sonication the temperature in the donor compartment was continuously monitored and maintained at 31 degrees C by the cooling c oil. Diffusion of the tritiated drugs (hydrocortisone, mannitol, oestr adiol) across hairless mouse and whole human skin was determined by li quid scintillation counting for up to 24 h, and the steady-state flux was determined. No enhancement in steady-state diffusion rates was obs erved for the three drugs in comparison with controls. The thermal eff ect of ultrasound seems to be the main factor which enhances percutane ous administration under the conditions used in physical medicine. (C) 1998 Elsevier Science B.V. All rights reserved.