Comparative Study on the effect of Hydrophilic and Hydrophobic Polymers on the Dissolution Rate of Metformin-gliclazide Extended-release Bilayer Tablet

Pharmaceutical scientists currently employ a range of strategies to maintain constant blood concentrations of therapeutic medications. When it comes to treating type 2 diabetes, metformin hydrochloride and gliclazide are the most recommended anti-diabetic medications. In general, to formulate a controlled-release drug hydrophilic polymers are commonly used as it is widely available and ease of its usage. In order to identify which kind of polymer is best for the release of both active components, this study employed hydrophilic and hydrophobic polymers at different concentrations. The tablets were compressed using direct compression method with a 21 mm oblong concave punches and upon compression the tablets were tested for their physical parameters such as diameter and thickness, mechanical characteristics such as hardness and friability, in-vitro drug release and drug release kinetics as per the USP and ICH guidelines. All the prepared formulations were evaluated via the in-vitro study to observe which formulations shows the highest similarity factors (f₂) when compared to the Reference Product. It was obtained that F6 containing 25% of HPMC (Shin Itsu) as polymer with Metformin as the active ingredient has a similarity factor of 55.0% when tested against the Reference Product. Meanwhile, F1 containing 45% of Methocel (K100) as polymer with Gliclazide as the active ingredient has a similarity factor of 55.3% when tested against the Reference Product. This indicates that the hydrophilic polymers that were incorporated into the formulation of the two active ingredients enhanced their release yet, the brands and concentrations of these polymers differ. Final locked formula (F17) was compressed as a bilayer tablet consisting Metformin with 25% of HPMC polymer and Gliclazide with 45% of Methocel polymer, tested for in-vitro study against the Reference Product was observed to achieve a similarity factor of more than 50% for both the active ingredients. A drug-excipient compatibility study was also conducted for the finalized formula in order to ensure there are no interference between both the drugs and excipients used. The release of drug from the marketed preparation and matrix preparation (F17) was found to be a diffusion drug mechanism for Metformin and erosion drug mechanism for Gliclazide as per Korsmeyer-Peppas equation.