Dieter Beutner

In vitro assessments of transdermal devices containing nitroglycerin

Abstract The in vitro rates of release of nitroglycerin from a number of products have been determined. The rates were measured in the absence of any skin, with dermatomed skin and skin that had been damaged by successive tape stripping. The results demonstrate the need for care in the interpretation of the data. If conventional Franz-type diffusion cells are used to monitor the rates of release where there is no rate-controlling membrane, it is possible to obtain erroneous results. This is caused by diffusion of additional drug from the polymer that is sandwiched between the ground glass edges of the cell. Considerable ‘edge effects’ are possible.