Effect of modification of formulation variables on physical characterization of superporouse hydrogel

Superporouse hydrogel (SPH) is widely used and investigated as a gastro retentive drug delivery system to extend drug residence time in the stomach   However, their mechanical strength represents a problem because they need to withstand the peristaltic movement of the stomach. Properties of SPH are widely affected by the materials used for their synthesis. The aim of the research is to study the effect of changing the foaming agent and foam stabilizer amount on physical properties, in particular mechanical strength, and drug release from SPH. Trifluoperazine HCl will be used as model drug in the study. SPH formulations was prepared using fixed amount of acrylamide (AM) and polyvinyl alcohol (PVA) as monomers, polyethylene glycol diacrylate (PEGDA) as cross-linker, TRFP as model drug and variable amount of sodium bicarbonate (NaHCO3) as foaming agent, and tween 20 as foam stabilizer.  Ammonium persulphate (APS) / tetramethyl ethylenediamine (TEMED) system was used as polymerization initiator. The effect of changing foaming agent and foam stabilizer on mechanical strength, buoyancy, porosity, density, drug release, drug content, swelling ratio, and swelling time was investigated. Modifying both factors affected all the physical properties and drug release profile. When tween 20 was increased the mechanical strength, density and floating lag time was increased with a reduction in porosity and drug release. While increasing NaHCO3 reduced mechanical strength, density and floating lag time with increased porosity and faster drug release was observed.   Optimum physical properties were observed in formula 2 which had 230 µl of Tween 20 (v/v) and 50 mg of NaHCO3 in which the mechanical strength was 579±0.4, floating lag time 14 min and 80% of the drug was released within 12 hr.  As a conclusion SPH with improved mechanical strength, physical properties and drug release pattern can be achieved by changing foam stabilizer and foaming agent amount in the formulations.