Abstract
Purpose: To prepare and evaluate metformin microspheres for prolonged release.Methods: Metformin microspheres were prepared by non-aqueous solvent evaporation method using various polymers, including ethylcellulose (EC), hydroxypropyl methylcellulose (HPMC), carbopol 934P (CA) and chitosan (CH). The effect of process variables, viz, drug/polymer ratio, stirring rate and type of polymer on the mean particle size, drug entrapment efficiency, yield, drug content, micromeritic properties and drug release of the microspheres were studied.Results: It was observed that as the stirring speed increased from 600 to 1800 rpm, microsphere size decreased and hence drug release rate increased. Drug release rate at 1:2 drug: polymer for microspheres produced at a stirring rate of 1200 rpm was in the following order: carbopol 934P > HPMC > ethyl cellulose > chitosan. The formulations containing carbopol 934P (CA3) and HPMC (HPMC3) released drug faster than chitosan microspheres (CH3).                                                   Conclusion: Amongst the developed microspheres, CH3 formulation (with chitosan as the polymer) exhibited maximum prolonged drug release at gastrointestinal pH or at least 15 h. This oral sustained metformin formulation could potentially improve the bioavailability of the drug as well as patient compliance.Keywords: Metformin, Microspheres, Prolonged release, Solvent evaporation, Ethylcellulose, Hydroxypropyl methylcellulose, Chitosan
Highlights
Microspheres have gained wide acceptance as a means to achieve oral and parenteral controlled drug delivery systems
Metformin microspheres were prepared in varying drug/polymer ratio while keeping stirring speed (1200 rpm) constant
Scanning electron microphotographs showed that the microspheres were spherical with a smooth to rough surface (Fig 1)
Summary
Microspheres have gained wide acceptance as a means to achieve oral and parenteral controlled drug delivery systems. They often require a polymer as carrier as well as core material [1]. A non-ionic, inert hydrophobic, non-biodegradable and biocompatible polymer with minimal toxicity It is one of the extensively studied encapsulating materials for the controlled release of pharmaceuticals [2]. Chitosan, a cationic polymer, has attracted particular attention It is biocompatible, biodegradable and bioadhesive at physiological pH and possesses OH and NH2 groups that can give rise to hydrogen bonding. Metformin microspheres were prepared in varying drug/polymer ratio (see Table 1) while keeping stirring speed (1200 rpm) constant. Microspheres were prepared at various stirring rates (i.e., 600, 1200 and 1800 rpm) while keeping drug/polymer ratio constant at 1:2
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