Development and characterization of bilayered tablets of diazepam for oral drug delivery: design, optimization and evaluation.

The oral bioavailability of drugs can be limited by their short residence time in the gastrointestinal tract. This study was performed to design bilayered floating tablets of diazepam comprising immediate-release and controlled-release layers. The tablets were prepared using sodium starch glycolate, polyvinyl pyrrolidone, hydroxypropyl methylcellulose and microcrystalline cellulose and evaluated for their characteristics. The optimized formulation was found to be buoyant for 8 h on simulated gastric fluid. Hydroxypropyl methylcellulose K4M and microcrystalline cellulose sustained the release of diazepam from the controlled-release layer. The optimized formulation exhibited an extended release period of 8 h. It can be concluded that bilayered tablets of diazepam may extend the residence time of the drug at the site of absorption.