In Vitro and In Vivo Evaluation of pH-Sensitive Hydrogels of Carboxymethyl Chitosan for Intestinal Delivery of Theophylline

Chitosan is a natural polymer which has limited solubility. Chitosan gets solubilized at acidic pH but is insoluble at basic pH. In the present study, carboxymethyl chitosan (CMC) was prepared which shows high swelling in basic pH and thus can delay the drug release and can act as matrix for extended release formulation. CMC was characterized by FTIR and NMR. pH-sensitive hydrogels of theophylline were formulated using CMC and carbopol 934. Hydrogels were evaluated for swelling, drug content in vitro drug release studies, and in vivo studies on rabbit. The swelling studies have shown little swelling in acidic pH 432% at the end of two hours and 1631% in basic pH at the end of 12 hours. The release profile of the formulation I containing CMC and carbopol in 1 : 1 ratio showed sustained release. In vivo studies showed that the release of theophylline from the prepared hydrogel formulation (Test) exhibit better prolonged action when compared to (standard) marketed sustained release formulation. The studies showed that the pH-sensitive hydrogel of CMC can be used for extended release of theophylline in intestine and can be highly useful in treating symptoms of nocturnal asthma.