The release mechanism of drags from polyurethane transdermal delivery systems

Polyurethane sheets-Synthaderm-have been used as carriers for iodine delivery. The release profiles of iodine in vitro have been found to be highly sensitive to changes in the device rotational speed: at high rpm the matrix diffusion mechanism controlled the system while at lower rpm the drug was released following a zero-order process. At low rotation conditions the major barrier for drug release, was found to reside in a boundary diffusion layer. Thus for transdermal delivery systems, devices applied to the skin in non-stirred environments and designed as solvated matrices, a boundary solvent layer formed at the device-skin interface may provide zero-order release patterns.