Development of Bilayer Tablet Containing Saxagliptin Immediate Release and Metformin Sustained Release Using Quality by Design Approach

Abstract

Objective: Adequate glycemic control in diabetes patients requires oral combination therapy. Saxagliptin is a dipeptidyl peptidase-4 inhibitor having less adverse effects and metformin is a first line medicine for diabetes treatment. The aim of this research work is to develop a bilayer tablet of saxagliptin and metformin in fixed dose combination (FDC) using quality by design (QbD) to acquire immediate release of saxagliptin and sustained release of metformin from bilayer tablet to ultimately achieve superior patient compliance. Methods: The development of the bilayer tablet was done in four stages using QbD. In first step, quality target product profile (QTPP) of bilayer tablet was defined and critical quality attributes (CQAs) were identified by risk estimation matrix and taguchi design, an immediate release saxagliptin layer was optimized in second step, optimization of sustained release metformin layer was carried out in third step and in final step bilayer tablet was prepared and characterized. The effect of independent parameters i.e. magnesium stearate level (X1), kneading time (X2) and lubrication time (X3) on Carr’s Index (Y1), percentage relative standard deviation of content uniformity (Y2) and drug release at 30 minute (Y3) were estimated for optimization of immediate release saxagliptin layer using Box-Behnken design (BBD). The effect of independent parameters i.e. hydroxypropyl methyl cellulose level (X4), compritol level (X5) and magnesium stearate level (X6) on Carr’s Index (Y4), drug release at 2 h (Y5), drug release at 5 h (Y6) and drug release at 10 h (Y7) were estimated for optimization of sustained release metformin layer using BBD. Results: The optimized composition of immediate release saxagliptin layer estimated using numerical optimization by Design expert was 0.88% (X1), 15 minutes (X2) and 3.85 minutes (X3) with predicted variables i.e. 10.59% (Y1), 3.16% (Y2) and 85% (Y3). The optimized composition of sustained release saxagliptin layer predicted through numerical optimization was 30% (X4), 3.36% (X5) and 0.9% (X6) having 10.89 % (Y4), 43.44 % (Y5), 60% (Y6) and 85.14% (Y7). In-vitro dissolution study of bilayer tablet showed immediate release of Saxagliptin (approximately 85% in 30 minute) and sustained release of metformin illustrating 43.21±1.21, 60.86±2.96 and 86.26±1.38% drug release at 2, 5 and 10 h, respectively. The release exponent for Korsmeyer-Peppas model for Saxagliptin and metformin was 0.237 (<0.45) and 1.536 (n>0.85) indicating Fickian and super case II transport drug release behavior, respectively. Conclusion: By QbD approach, bilayer tablet containing saxagliptin and metformin was successfully developed and influence of various formulation parameters on CQAs of drug products was understood with fewer experiments. This leads to conclusion that cost can be reduced using QbD in development of FDC for improving patient compliance.