Formulation and Development of Gastroretentive Dipyridamole Microspheres: Proof of Concept by In vitro-In vivo Assessment

Abstract

The present research was aimed at development and optimization of dipyridamole gastroretentive microspheres. Gastro retention was achieved using swellable polymeric material such as hydroxypropylmethylcellulose K4M, ethyl cellulose as release retardant using solvent diffusion evaporation method. 32 factorial design was applied for the development of best optimized formulation. The design was developed by considering two independent variables, ethyl cellulose, and stirring speed. Their effect on drug release, entrapment efficiency, particle size was analysed using response surface methodology. Formulation B1 among all formulations tested was found to be the best as it demonstrated prolonged floating time, maximum entrapment efficiency and drug release in a controlled manner. Formulation B1 was characterized further for presence of residual solvent by gas chromatography/mass spectrometry and the result showed absence of residual solvent. Gastro retention was assessed using the in vivo gamma scintigraphy technique in Albino rabbits and the results indicated prolonged gastric retention. Pharmacokinetic study comparing pure dipyridamole and dipyridamole microspheres was conducted and Cmax, Tmax and Kel were estimated. In vitro-in vivo correlation was determined using Wagner-Nelson function. Pharmacokinetic study revealed improved bioavailability (30 %) as compared to pure dipyridamole. Good correlation was obtained with a regression coefficient of 0.9704. The in vivo gamma scintigraphy and pharmacokinetic studies confirmed gastric retention of the prepared dipyridamole floating microspheres. Accelerated stability studies indicated integrity of the developed formulation.