Metoclopramide exhibits variable bioavailability when administered orally. Incorporating it into an appropriate dosage form can enhance its bioavailability. Example of such dosage form are buccal films, which enable direct absorption of the drug into the systemic circulation, there by bypassing first-pass metabolism and improving bioavailability.
Using the solvent casting method, we prepared bilayer buccal films containing metoclopramide, with a backing layer thickness of 110 µm (formulations "E") from 11 base solutions with different proportions of metoclopramide, carrier polymer, plasticizer, water and pH value of base solution. The backing layer consisted of 20% hydroxypropylcellulose.
Drug release from the bilayer buccal films was evaluated using two methods - a USP I and innovative cell for release of films. Release profiles were compared to those of previously studied monolayer films (formulations »M«) and bilayer films with a backing layer thickness of 70 µm (formulations »D«) using the similarity factor f_2. Both methods showed that the »E« formulations exhibited lower variability in release profiles and a slower release rate compared to earlier formulations. The variability in the thickness of the backing layer has the greatest impact on the variability of the release profiles of bilayer buccal films. With increasing thickness of the backing layer, the variability lowers. Both methods can distinguish between the release profiles of formulations »M« and »E«, but only the innovative cell for release of films demonstrated the ability to distinguish between formulations »D« and »E«. It was not possible to compare the ranking of release profiles to formulations »D« because the variability within the »E« formulations was greater than the differences between individual profiles.
Near-infrared spectroscopy revealed that the metoclopramide content varied within individual formulation. Raman microscopy revealed that the application of the backing layer affected the composition of the base layer, as metoclopramide migrated from the base to the backing layer.
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