Preparation and Evaluation of Bioadhesive Microspheres Prepared by Ion Gelation Method and Effect of Variables on Quality of Microspheres

Gastroretention is advisable for metformin hydrochloride due to its site specific absorption and low bioavailability (60%). Therefore, the attempts have been carried out in present study to formulate bioadhesive microspheres of metformin hydrochloride. Microspheres provide precise control on drug release and bioadhesion is useful to obtain gastroretention for improvement in bioavailability. Drug loaded microspheres of bioadhesive polymers were prepared by ionic gelation method. Hydroxypropyl methyl cellulose (HPMC), hydroxypropyl cellulose (HPC) and methyl cellulose (MC) were used as bioadhesive polymers. Microspheres were prepared by using various ratios of sodium alginate to respective polymer(s). One gram of drug was added in 50ml solution of polymers separately. Microspheres were collected in 10% w/v calcium chloride solution with constant stirring. Formulation MS2 (sodium alginate: HPC; 1:1) was found to be the best among all. For MS2, percent yield (65.5%), drug entrapment efficiency (72±0.56%), particle size (851 µm), in vitro wash off test (63.9 %), in vitro drug release (80.77 %) etc. Some process parameters viz orifice diameter of needle used to pass polymer solution, dropping height and stirring speed were studied. It was observed that as the orifice diameter of needle decreased from needle no. 18 to 23, the microspheres were more spherical with retention in their shape and needle no. 20 was found to be optimum. More spherical microspheres were observed with decrease in dropping height and optimum was found to be 6 cm. With increase in stirring speed from 250 to 750 RPM, drug entrapment efficiency decreased.