Polyethyleneimine-treated xanthan beads for prolonged release of diltiazem: in vitro and in vivo evaluation

The purpose of the study was to develop a multiunit sustained release dosage form of diltiazem hydrochloride using a natural polymer, sodium carboxymethyl xanthan gum and polyethyleneimine (PEI) from a completely aqueous environment. PEI treated diltiazem resin complex loaded beads were characterized by morphology, drug entrapment efficiency, in vitro and in vivo release behaviour. 40% and 80% drug was released in 2 hour in pH 1.2 and in 5 to 6 h in pH 6.8 respectively depending on the formulation variables. The prolonged release was attributed to decreased swelling of the beads due to PEI treatment. Maintaining the shape throughout the dissolution process, PEI treated diltiazem resin complex beads released the drug following non-Fickian transport phenomena. In vivo pharmacokinetic evaluation in rabbits shows slow and prolonged drug release when compared with diltiazem solution. The designed beads are suitable for prolonged release of a water soluble drug under a complete aqueous environment using natural gum.