Evaluation of two novel plant gums for bioadhesive microsphere and sustained-release formulations of metformin hydrochloride.

Abstract

The biological half life of metformin requires multiple doses which are associated with poor patient compliance. This justifies the need for a dosage form with reduced dosing frequency. Gums from Enterolobium cyclocarpum and Cedrela odorata trees were evaluated in formulating bioadhesive microspheres containing metformin hydrochloride, for sustained drug release. Hydroxylpropylmethyl cellulose (HPMC) was the standard. Microspheres were produced from formulations of API and either cedrela gum (FC), enterolobium gum (FE) or HPMC (FH), using a W/O solvent extraction technique. The microspheres were characterized using a particle size analyzer, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), powder X-ray diffractometer (PXRD), drug entrapment, in vitro release and mucoadhesion studies. The data was analyzed using ANOVA and t-test at p = 0.05. FT-IR spectroscopy indicated no alteration in the functional groups of metformin. A yield of 92-98% microspheres was obtained from all the formulations which had a particle size range of 72-84 μm. SEM revealed cylindrical to near-spherical particles with rough surfaces. The drug release profile showed a burst over the first 30 min followed by a steady release for about 5 h and a slow release for 5 days. Formulations containing the gums sustained the release of API for almost the same time as HPMC formulations; the ranking order was FE > FH > FC (p > 0.05). All the formulations exhibited good concentration-dependent mucoadhesive properties. The gums were suitable for formulation of mucoadhesive microspheres for sustained release of metformin. The formulations showed good release properties in an alkaline pH.