Influence of drug-polymer ratio on physical characteristics and release of metformin hydrochloride from metforminalginate microspheres

Purpose : To investigate the effect of drug and polymer ratio on the physical characteristics and release rate of metformin hydrochloride from alginate microspheres. Methods : Microspheres were prepared by ionotropic gelation aerosolization technique using sodium alginate as polymer and calcium chloride as crosslinker. Three formulations of drug and alginate polymer ratios: 1:1 (F1); 1:1.5 (F2); and 1:2 (F3), and 10 % calcium chloride (CaCl 2 ) were investigated. The microspheres were studied with respect to physical characteristics, release profile and release rate. Release evaluation was done at pH 1.2 in hydrochloric acid (HCl) for 2 h, and in phosphate-buffered saline (PBS) at pH 7.4 for 12 h. Results : Drug loading in formulations F1, F2 and F3 were 3.08 ± 0.21, 3.34 ± 0.28, and 3.99 ± 0.19 %, respectively. Low entrapment of below 15 % was achieved for all formulations, whereas high yield (above 45 %) was obtained. Drug release above 74 % was observed for all formulations. The release rates of F1, F2 and F3 were 9.6390 x 10 -2 , 9.0985 x 10-2, and 8.3312 x 10 -2 %/min, respectively. Conclusion : Metformin-alginate microspheres can be used for optimized formulations with good physical characteristics and in vitro release. These findings suggest that the microspheres might be a potent drug delivery system for the treatment of diabetic mellitus. Keywords : Metformin, Alginate microspheres, Drug-polymer ratio, Aerosolization, Drug release