Preparation, optimization and in vitro–in vivo investigation for capsules of the choline salt of febuxostat

Abstract

The objective of the present study was to exhibit the enhanced water-solubility and in vivo oral absorption when febuxostat (FXT) became the salt formation of choline. The formation of the choline salt of febuxostat was confirmed by X-ray powder diffraction, infrared spectroscopy analysis and differential scanning calorimetry. The direct filling method was used to develop a capsule formulation. Cellactose 80 was used as the filler due to its good fluidity, while cross-linked polyvinylpyrrolidone (PVPP) and magnesium stearate (MS) were used as the disintegrant and lubricant, respectively. Then the in vitro release of the formulation was carried out in five different dissolution media including HCl solution (pH 1.2), acetate buffer (pH 4.5), phosphate buffer (pH 6.8 and pH 7.2) and water. Evident improvement of release for choline febuxostat (CXT) was presented in water while the dissolution degree was decreased for CXT in the medium of phosphate buffer (pH 6.8) in comparison with FXT. Furthermore, the pharmacokinetics of CXT was studied in rats using UPLC-MS/MS compared with FXT. The data acquired illustrated that AUC0-24h of CXT and FXT were 22,245.96 ± 7342.92 µg⋅h/l and 12,249.70 ± 2024.04 µg⋅h/l, respectively. The relative bioavailability of CXT to FXT was about 181.6% and the P value of AUC0-24h was less than 0.05. It showed significant difference between the two drugs after oral administration. In conclusion, the water-solubility and oral bioavailability were both improved remarkably for the choline salt of febuxostat and choline salinization was proved an effective way to increase the in vivo absorption for FXT.