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The development of an adhesive bond between the patch and the intestinal wall can be visualized as a two step process.

• Initial contact between two surfaces.
• Formation of secondary bonds due to non-covalent interactions.

There are many theories proposed for the adhesion of the polymeric patches with the gastrointestinal mucosa. Wetting theory, diffusion theory, electronic theory, adsorption theory are some of those mechanisms.

The evaluation of the prepared patch can be done by both in vitro and in vivo techniques. Bioavailability, release pattern and bioadhesion of the patch can be determined by these techniques. In vitro evaluation includes methods like: shear stress management, detachment force measurement, mucoadhesion studies and adhesion force measurement. While x-ray techniques are the most important evaluation methods used for the in vivo studies.