The objective of the present work undertaken was to enhance the solubility and dissolution rate of valsartan a poorly water soluble antihypertensive, by preparation of solid dispersion granules which would additionally allow easy compression into tablets. The dispersion granules were prepared using a hot melt granulation technique which involved preparation of a homogenous dispersion of valsartan in gelucire-50/13 melt, followed by its adsorption on to the surface of aeroperl-300pharma®, an inert adsorbent. A two-factor, three-level (32) statistical design was implemented to quantitate the influence of gelucire-50/13 and aeroperl-300pharma on the dissolution profile and flow properties of the dispersion granules, where gelucire-50/13 and aeroperl-300pharma® were chosen as independent variables, while dissolution and flow properties were chosen as dependent variables. The dispersion granules were characterized for their in-vitro dissolution rate and flow properties. An appropriate statistical model was arrived at and a significantly enhanced dissolution rate and flow properties were exhibited with the optimized formulation. The formulation was further characterized by FTIR, DSC, XRD and SEM analysis. FTIR spectrum revealed some drug excipient interactions. DSC and XRD data indicated the retention of amorphous form of valsartan. SEM confirmed the homogeneity and surface adsorption of the gelucire- 50/13 melt on aeroperl-300pharma® leading to enhanced surface area and thus dissolution rate. The tablets of optimized dispersion granules were formulated and evaluated. The in-vitro dissolution rate of these tablets was significantly better in comparison with marketed formulation. In conclusion the statistical model enabled us to understand the effects of formulation variables on the dispersion granules of valsartan.
Keywords: Valsartan, dissolution, flow properties, optimization, dispersion granules, solid dispersion