To design, formulate and test the in vitro dissolution of new oral dosage forms of metformin hydrochloride (MH) in semisolid polymeric matrices having sustained-release properties suitable for once-a-day or twice-a-day administration that would increase MH bioavailability and also address the shortcomings in the currently marketed sustained-release tablets.


MH was dispersed in molten polymeric matrices composed of various proportions of high molecular weight hydrophilic polymers, hydrophobic oily semisolid excipients, and muco-adhesive polymeric materials. Thermal analysis and X-ray diffractometry was carried out on the prepared semisolid matrices. Four prepared formulations each of which containing 400mg MH were filled into size zero hard gelatin capsules (HGC) and were subjected to in vitro dissolution testing using USP basket method at 50rpm using 1000ml distilled water as dissolution medium. MH was analyzed using UV spectrophotometric analysis. Glucophage® 500mg tablets were used as a reference.


The prepared formulations resulted in extended-release profiles that lasted between 6-8 hours and demonstrated bimodal release pattern which characterizes the release from mixes of triglycerides with polyethylene glycol esters of fatty acids. The incorporation of PEG 6000 or PEG 35000 resulted in an overall faster dissolution rate compared to other formulations with complete release achieved after 6 hours. On the other hand, PEG400 incorporation to the formulation resulted in a fast initial release followed by a slower release rate following the first 3 hours. Thermal and X-ray analysis of the formulations showed changes in MH crystallinity.


Capsules formulated using semisolid matrices showed promising results in extending the release of MF compared to the marketed tablets. However, bioavailability studies to test the ability of those Gelucire-based capsules of MF to improve its bioavailability and residence time are future plans.


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  1. H.M. Younes, Are novel semisolid filled hard gelatin capsules superior to currently marketed metformin tablets?, QFARF Proceedings, 2010, BMO12.
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