Solid dispersion of dutasteride using the solvent evaporation method: Approaches to improve dissolution rate and oral bioavailability in rats

The aim of this study was to develop a dutasteride (DUT) solid dispersion (SD) using hydrophilic substances to enhance its dissolution (%) and oral bioavailability in rats. DUT-SD formulations were prepared with various copolymers using a solvent evaporation method. The physical properties of DUT-SD formulations were confirmed using field emission scanning electron microscopy (FE-SEM), differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD), and attenuated total reflectance Fourier transform infrared (ATR-FT-IR) spectroscopy. The toxicity and oral bioavailability of DUT-SD formulations were evaluated. Tocopheryl polyethylene glycol-1000-succinate (TPGS) was chosen as the solubilizer; and methylene chloride, and Aerosil (R) 200 or micro crystalline cellulose (MCC) were chosen as the solvent and carrier, respectively, based on a solubility test and pre-dissolution study. The dissolution levels of DUT-SD formulations were 86.3 +/- 2.3% (F15) and 95.1 +/- 1.9% (F16) after 1 h, which were higher than those of the commercial product, i.e., Avodart (R) (75.8 +/- 1.5%) in 0.1 N HCl containing 1% (w/v) sodium lauryl sulfate (SLS). The F16 formulation was found to be stable, after assessing its dissolution (%) and drug content (%) for 6 months. The DUT-SD formulations resulted in relative bioavailability (BA) values of 126.4% (F15) and 132.1% (F16), which were enhanced compared to that of Avodart (R). Dissolution (%) and relative BA values were both increased by hydrogen interaction between TPGS and DUT. This study might contribute to a new formulation (powder) whose oral bioavailability is greater than that of Avodart (R) (soft capsule), which could facilitate to the use of the SD system during the production process.