Optimization of amorphous solid dispersion techniques to enhance solubility of febuxostat

Febuxostat is a selective inhibitor of xanthine oxidase and belongs to BCS class II drugs having low solubility and high permeability. Solubility is the most important parameter which directly affects dissolution, absorption and bioavailability of the drugs. There are different techniques by which we can improve solubility and dissolution rate of poorly soluble drug. Amorphous solid dispersion is one of the methods which can improve solubility as well as powder characteristics. The aim of the present study was to formulate and optimize various methods of formulating solid dispersion by using various drug-to-polymer ratios and identifying the batch which gives higher solubility as well as amorphous powder of the drug febuxostat. Different techniques like hot melt method, solvent evaporation method and spray drying techniques were selected for optimization. Attempts were made to improve solubility of febuxostat by employing Kolliphor P 188, Kolliphor P 237, Eudragit RLPO in different drug-to-polymer ratios (1:1, 1:1.5, 1:2) as carrier. The prepared solid dispersion was characterized for the saturation solubility, percentage yield, using differential scanning calorimetry (DSC), scanning electron microscopy (SEM), powdered X-ray diffraction studies (PXRD), and residual solvent determination. Solid state characterization indicated that febuxostat was present in the amorphous form after mixing with polymeric carrier. In contrast to the pure form of drug, solid dispersion of the drug showed better solubility and amorphous characteristics which can be attributed to decreased crystallinity due to hydrotrophy. Thus, amorphous solid dispersion approach can be used successfully to enhance solubility, dissolution rate and bioavailability of febuxostat.