Metoclopramide is an active pharmaceutical ingredient with very variable bioavailability when orally administered. Buccal films are a newer dosage form that offers certain advantages over oral forms. They can improve bioavailability and reduce its variability.
We have prepared buccal films using the solvent casting method with help of an applicator. This allowed us to control the thickness and ensure even application. Sodium alginate was used as the carrier polymer, and xylitol acted as a plasticizer. Using the design of experiments (DoE) method, we created 11 different formulations, we varied the proportions of the composition and pH. We also made bilayer films to compare the effect of an additional directing layer on the release profiles. The additional layer consisted of hydroxypropyl cellulose.
For the evaluation of release, we used two methods, the first was the standard basket apparatus, and the second was our own innovative method based on a flow cell. The second one allows for better differentiation between release profiles. We found that the most important factor affecting the release rate is the proportion of sodium alginate. In bilayer buccal films, we observed a significant reduction in release rate and the variability of their profiles. We also made different thicknesses of certain formulations and found that a thicker directing layer further slows the release and reduces the standard deviation within them. We also measured contact angles and found that they can serve as a rough estimate of their properties.
We found that viscosity does not affect the formation of crystallization and that the proportion of xylitol has the most significant impact. A higher proportion of xylitol results in less crystallization. The formation of crystals was also confirmed by Raman microscopy. With the additional directing layer, the crystals dissolve again, and the films become transparent.
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