Influence of colon degradation of polysaccharide on the oral bioavailability of theophylline from controlled release hydrophilic matrices.

Abstract

Hydrophilic matrices of gum karaya (GK) and guar gum (GG) using theophylline (TH) as a model drug were prepared for oral controlled release. In vitro release studies were performed for these matrix systems to find out the suitable drug-carrier ratio, which extend the drug release up to 24 h. Promising matrix systems were subjected for in vitro degradation studies in the presence of rat caecal contents. These matrices were also evaluated for their in vivo performance in healthy human volunteers. Matrix systems containing 40% w/w of polysaccharide (GK or GG) have shown uniform and similar in vitro drug release profile for 24 h in the Sorenson's phosphate buffer (pH 7.4). However, TH release from GG-TH matrix system in the presence of rat caecal contents was significantly higher than that from GK-TH matrix system. This is because of the susceptibility of GG for degradation by microorganisms present in the rat caecal content. Though there was no significant difference between the peak plasma concentration (Cmax) and time of its occurrence (Tmax) for TH from GG-TH and GK-TH matrix systems, it was found that oral bioavailability of TH from former matrix was significantly higher than that of later. Therefore, the present study disclosed that the usage of colon degradable polymer offers an advantage in the design of controlled release dosage forms of drugs, which has good absorption properties throughout the gastrointestinal tract.