Thermally reversible xyloglucan gels as vehicles for oral drug delivery

Abstract

The potential, as sustained release vehicles, of gels formed in situ following the oral administration of dilute aqueous solutions of a xyloglucan polysaccharide derived from tamarind seed has been assessed by in vitro and in vivo studies. Aqueous solutions of xyloglucan that had been partially degraded by β-galactosidase to eliminate 44% of galactose residues formed rigid gels at concentrations of 1.0 and 1.5% w/w at 37°C. The in vitro release of indomethacin and diltiazem from the enzyme-degraded xyloglucan gels followed root-time kinetics over a period of 5 h at 37°C at pH 6.8. Plasma concentrations of indomethacin and diltiazem, after oral administration to rats of chilled 1% w/w aqueous solutions of the enzyme-degraded xyloglucan containing dissolved drug, and a suspension of indomethacin of the same concentration were compared. Constant indomethacin plasma concentrations were noted from both formulations after 2 h and were maintained over a period of at least 7 h. Bioavailability of indomethacin from xyloglucan gels formed in situ was increased approximately threefold compared with that from the suspension. The results of this study suggest the potential of the enzyme-degraded xyloglucan gels as vehicles for oral delivery of drugs.