The physical and antibiotic properties of kanamycin powders obtained by spray freeze drying (SFD) were compared with those of raw kanamycin. The SFD procedures were optimized to prepare kanamycin for use as an inhaled drug. Scanning electron microscopy (SEM) and a laser particle size analyzer were applied to estimate physical structure and properties of the particle. In addition, the disk diffusion method was used to compare the antibiotic activity of raw kanamycin and that produced by SFD. According to SEM, the kanamycin particles had various sizes and shapes with porous structures at different SFD conditions. The diameters of the kanamycin powders were between 13.5 mu m and 21.8 mu m, and their aerodynamic particle sizes were between 3.58 mu m and 639 mu m. The antibiotic activities of the raw and spray freeze-dried kanamycin samples were not significantly different (P>0.05). The optimized conditions for annealing temperature, annealing time, kanamycin concentration, pressure, and nozzle tip lift were -15 degrees C, 5 h, 10% kanamycin, 100 kPa, and, 1 mm, respectively. (C) 2010 Elsevier B.V. All rights reserved.