In vitro and in vivo-release of nitroglycerin from a new transdermal therapeutic system.

A new transdermal therapeutic system (TTS) for nitroglycerin is presented that controls release of the active substance by means of desorption and diffusion. The drug release, in the dosage range examined under sink conditions, is independent of electrolytes and pH of the aqueous acceptor medium, but it does depend on its temperature as expected. Batches obtained on a production scale were highly reproducible. The validity of an "in vitro" dissolution model is demonstrated by the good correlation between the amount of nitroglycerin liberated "in vitro" and "in vivo". The amount of nitroglycerin released in vivo is approximately 10 µg/cm(2)/h from 4 hours after application, and, it is controlled by the system.