Thermal effect of ultrasound enhancer for transdermal insulin delivery

Abstract

Ultrasound has been known as a good enhancer for transdermal drug delivery. However, major mechanisms in the ultrasound enhancer to improve the transdermal drug delivery were not well understood. In this study a simple experiment was designed to simulate the human skin system with rat back skin. An unfocussed 1-MHz ultrasound transducer and a heating wire loop were used as enhancers. Transmitted amounts of insulin with the ultrasound enhancer were increased ten times more than those without any enhancer. The ultrasound enhancer also improved by 25% the enhancement of insulin transportation compared with that due to thermal effect solely by heating wire loop. It was also observed that rapid temperature increase with ultrasound more efficiently enhanced transdermal transport of insulin. The thermal effect of the ultrasound enhancer is suggested as a most likely mechanism for transdermal insulin delivery.