Preparation of Gastro-retentive Tablets Employing Controlled Superporous Networks for Improved Drug Bioavailability.

The development of an oral formulation that ensures increased bioavailability of drugs is a great challenge for pharmaceutical scientists. Among many oral formulation systems, a drug delivery system employing superporous networks was developed to provide a prolonged gastro-retention time as well as improved bioavailability of drugs with a narrow absorption window in the gastrointestinal tract. Superporous networks (SPNs) were prepared from chitosan by crosslinking with glyoxal and poly(vinyl alcohol) (PVA). The SPNs showed less porosity and decreased water uptake with an increase in the crosslinking density and content of PVA. Gastro-retentive tablets (GRTs) were formulated using hydroxypropyl methylcellulose (HPMC, a hydrophilic polymer) and the prepared SPNs. Ascorbic acid (AA), which is mainly absorbed in the proximal part of the small intestine, was selected as a model drug. The formulated GRTs exhibited no floating lag time and stayed afloat until the end of the dissolution test. The in vitro drug release from the GRTs decreased with a decrease in the water uptake of the SPNs. The profile of drug release from the GRTs corresponded to the first-order and Higuchi drug-release models. Overall, floating tablets composed of the SPNs and HPMC have potential as a favorable platform to ensure sustained release and improved bioavailability of drugs that are absorbed in the proximal part of the small intestine.