In vitro release profile of estradiol transdermal therapeutic systems

The in vitro release profiles of two sizes of estradiol patches were determined by the paddle method, where the patch was held in position at the bottom of the dissolution vessel by sandwiching it between a watch glass and an aluminum wire mesh or Teflon screen, and also by the manufacturer's paddle-over-disk method. The estradiol content of test aliquots of the dissolution medium was determined by HPLC. The release profiles by both procedures were comparable and showed that approximately 10% of the labeled drug was released in 4 days.