Formulation and evaluation of pH sensitive poly(acrylic acid-co-hydroxy ethyl methacrylate) hydrogels for specific site drug delivery

The aim of the present study was to formulate the hydrogels of hydroxyethyl methacrylate (HEMA) and acrylic acid (AA) with two drugs namely; disopyramide phosphate (DSP) and propafenone hydrochloride (PPH) for pH sensitive drug delivery systems. These monomers were polymerized by free radical polymerization method and crosslinked with ethylene glycol dimethacrylate (EGDMA). The dynamic swelling and deswelling behaviors of the prepared hydrogels were studied by changing the pH from 1.2 to 7.4, varying copolymer compositions and crosslinker content. It was observed that with change in pH from 1.2 to 7.4, a considerable increase in swelling of about 70 % was observed for all formulations. It was also found that the degree of swelling increased with an increase in acrylic acid concentration and decreases with increase in EGDMA content. The drug loaded hydrogels were characterized by Fourier transmission infrared (FT-IR) spectroscopy, differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The prepared drug loaded hydrogels have been further evaluated for drug content, in vitro drug release and stability studies. The in vitro drug release profiles of both the drugs were almost similar indicating that release is independent of the drug used and also the formulations showed stability for about 30 days.