The hydrogels or polyelectrolyte systems are based on ionic cross linking. They have been employed to prepare a controlled release dosage forms. These systems are based upon the fact that their structure can entrap the drug within them. They normally employ a hydrophilic matrix system.
Metformin hydrochloride (MH) a Class III drug was used as the model drug. Metformin hydrochloride (MH) is a highly water soluble and low permeability drug. Thus, a controllable dosage form system for the controlled release of metformin hydrochloride (MH) was attempted. Metformin hydrochloride (MH) loaded chitosan polyelectrolyte complex (PEC) hydrogel beads were prepared via ionotropic crosslinking with sodium tripolyphosphate (TPP). A combination of various polymers were studied with chitosan having metformin hydrochloride (MH) dispersed within them. Thus, metformin hydrochloride (MH) dispersed in 1.5% glacial acetic acid and having chitosan and polymers dispersed within it was cross linked with 1% sodium tripolyphosphate solution adjusted to a pH of 6.0-6.4. The beads prepared were examined for the optimal stirring conditions and curing time in order to obtain spherical beads. The prepared beads were filtered and kept at 35°C overnight to dry. The ratio of polymer: drug combination was kept around 1:1. The physical and chemical characterization of the resultant beads was done to determine their particle shape, particle diameter, weight, percent swelling, DSC studies, drug entrapment efficiency (DEE) as well as in vitro release. Fourier Transform Infrared (FTIR) and Powder X-ray Diffraction (PXRD) studies were performed to determine any possible drug polymer interaction. The effect of incorporating polymers such as sodium alginate, xanthan gum, hydroxy propyl methyl cellulose, and hydroxy ethyl cellulose on the physico-chemical properties of the beads were also studied. Spherical to oval beads with varying particle size, weight, DEE, and sustained release profile were obtained depending on the polymer combination used. These beads were able to sustain the release of the metformin HCl from the beads. The in vitro dissolution studies were done to assess the release pattern of the drug from the beads over a five to six hour period. A sample volume of 5 mL was taken from the dissolution apparatus and the same amount was replaced with an equal volume of phosphate buffer to maintain the sink conditions. The in vitro dissolution rate profile showed a sustained release of the drug from the beads. The dissolution profile was observed to be similar in nature for all the polymers studied. The chitosan beads were subjected to stability studies for one month. The stability results for the chitosan beads after one month were shown to be favorable with respect to providing a possible controlled release dosage form from the beads.