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 (CaCl2) 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