Flow through diffusion cell method: A better approach to study drug release behavior as compared to traditional dissolution test method

Co-polymeric hydrogels consisting of N-vinyl-2-pyrrolidone (NVP) and acrylic acid (AAc) were synthesized and evaluated for release of a model drug, i.e., vitamin B-12. Release studies in simulated gastric fluid ( pH 1.2) and intestinal fluid ( pH 7.4), at 37 degrees C, showed the hydrogels to be pH sensitive. An in vitro release study by 'traditional dissolution test' (TDT) showed that percent drug released from the hydrogel was nearly 8.6 +/- 2.1 and 83.2 +/- 4.8 in the media of pH 1.2 and 6.8, respectively. However, in order to incorporate in vivo GI conditions such as acidic pH and high water content in the stomach, low water content and the presence of a semi - solid mass in the large intestine, a new test model, called flow through diffusion cell (FTDC) was also used. The two approaches yielded almost different release profiles. The gels were characterized by thermogravimetric analysis and FTIR spectroscopy.