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GTN-loaded adhesive film

Peelable protective film

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Adsorbent plus glyceryl trinitrate • Dissolved glyceryl trinitrate

Figure 8.41 Cross-section of Deponit TTS. Deponit contains glyceryl trinitrate directly embedded in a lactose-containing adhesive film approximately 0.3 mm thick. In cross-section, the Deponit transdermal system, closely resembling a plaster, consists of three components in macroscopic proportions, the ratios of which are as given in the figure. The adhesive film is both a store of active ingredient and the release-controlling matrix.

Reproduced from reference 14.

Summary

Although there is no strict boundary line, we have divided polymers into water soluble polymers and water-insoluble systems, typified respectively by materials used to prepare viscous solutions and those which function as barrier membranes or containers. In the first case we have considered the factors controlling their properties: the influence of molecular weight (distribution), branching, charge, flexibility, ionic strength and pH on solution properties. In the case of water-soluble polymers, the main concern has been with solute transport through the polymer bulk. Equations dealing with viscosity and with diffusion have been cited. The variety of pharmaceutical uses of polymers have been described, and the variety of morphologies that polymers can adopt has been emphasised: solutions, gels, microcrystals, crystals, fibres, and dendrimers.

When a polymer is being characterized for pharmaceutical use, therefore, much more than its molecular weight distribution should be determined. Its end use will, of course, determine the tests to be applied to any system.

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