System Components and Performance — GLUCOPHAGE XR comprises a dual hydrophilic
polymer matrix system. Metformin hydrochloride is combined with a drug release controlling
polymer to form an “inner” phase, which is then incorporated as discrete particles into an “external”
phase of a second polymer. After administration, fluid from the gastrointestinal (GI) tract enters the
tablet, causing the polymers to hydrate and swell. Drug is released slowly from the dosage form by
a process of diffusion through the gel matrix that is essentially independent of pH. The hydrated
polymer system is not rigid and is expected to be broken up by normal peristalsis in the GI tract.
The biologically inert components of the tablet may occasionally remain intact during GI transit and
will be eliminated in the feces as a soft, hydrated mass