Preparation and characterization of gastrointestinal wafer formulations

Many active pharmaceutical ingredients (API) have a very poor or highly variable bioavailability after oral administration. One possibility to overcome this problem might be found in the application of mucoadhesive dosage forms like gastrointestinal wafers. However, a currently unsolved challenge is the control of the adhesion of the wafer to the intestinal mucus. One suggested solution might be the combination of gastrointestinal wafers and expanding systems. Such a combination requires thin and elastic wafers which are further characterized by an unidirectional drug release. In this study gastrointestinal, twolayered wafers containing a water-insoluble backing layer and a drug-loaded, mucoadhesive layer were fabricated by casting solvent technique. The backing layer consists of Ethocel™ Standard 10 Premium and the mucoadhesive layer was prepared using a mixture of Methocel™ E15 Premium LV, polyvinyl alcohol and Macrogol 400. The wafers were characterized regarding their appearance, mechanical properties and dissolution profiles as well as the influence of backing layer thickness on drug transfer and their ability of unidirectional drug release. The wafers with backing layer thickness of 500μg Ethocel™/cm² presented adequate mechanical properties, a drug transfer about 73% and unidirectional drug release.