Abstract
For transdermal patches to function, the packaging material must not only prevent unwanted diffusion of the active ingredients, but also—in a seemingly contradictory fashion—permit controlled rates of penetration of the active ingredients through the skin side of the patch. Polyurethanes have a unique combination of properties includ ing good physical properties and an ability to transmit gas and vapor while acting as a barrier to liquids. These films can be produced with a broad range of controlled dif fusion rates. Urethanes can also be formulated to provide good biocompatibility and other needed features, such as solvent resistance and heat sealability. The result has been that urethanes have been used successfully for the production of several transdermal patches.
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