Improvement of the dissolution rate of nitrendipine using a new pulse combustion drying method.

Solid dispersions (SDs) of nitrendipine (NTD), a poorly water-soluble drug, were prepared with the Hypulcon pulse combustion dryer system, and the physicochemical properties of particles were investigated and compared with those of particles prepared with a spray dryer. The SD particles prepared with Hypulcon using Aerosil and Tween 80 as carriers showed improved properties over those prepared with a conventional spray dryer, such as smaller particle size, tighter particle size distribution, and no agglomeration. Powder X-ray diffraction and differential scanning calorimetry evaluation showed that the drug in the NTD-Aerosil SD prepared with 5% (v/v) Tween 80 solution was dispersed in an amorphous state. Fourier transformation IR spectroscopy indicated the presence of hydrogen bonds between NTD and Aerosil. Aerosil had greater ability to improve the dissolution of NTD than Sylysia and other polymers. The highest drug supersaturation concentration was maintained continuously during the dissolution test of the NTD-Aerosil SD prepared with 5% (v/v) Tween 80 solution using Hypulcon. The good hydrophilicity and dispersibility of Aerosil, solubilization of Tween 80, and actions of shock waves and ultrasonic waves might account for the amorphization of NTD and improved dissolution rate of SDs. Pulse combustion drying with low drying costs and high thermal efficiency is a promising method for the preparation of SD particles with improved properties without using organic solvent.