Nanosuspension formulations of poorly water-soluble compounds for intravenous administration in exploratory toxicity studies: in vitro and in vivo evaluation

This study was conducted to investigate the use of a nanosuspension for intravenous injection into dogs to increase exposure without toxic additives for preclinical studies in the discovery stage. Nanosuspensions were prepared with a mixer mill and zirconia beads with a vehicle of 2% (w/v) poloxamer 338, which was confirmed to lead to no histamine release in dogs. Sterilized nanosuspensions of poorly water‐soluble compounds, cilostazol (Cil), spironolactone (Spi) and probucol (Pro), at 10 mg ml−1 were obtained by milling for 30 min, followed by autoclaving for 20 min at 121 °C and milling for 30 min (mill–autoclave–mill method). The particle sizes (d50) of Cil, Spi and Pro were 0.554, 0.484 and 0.377 µm, respectively, and the percentages of the nominal concentration were 79.1%, 99.6% and 75.4%, respectively. In chromatographic data, no extra peaks were observed. The particle size of Cil was 0.564 µm after storage for 16 days at 2–8 °C. Cil in nanosuspension, but not in microsuspension, rapidly dissolved in dog plasma. Cil nanosuspension at 0.4 mg kg−1 and Cil saline solution at 0.03 mg kg−1, around the saturation solubility, were intravenously administered to dogs. Nanosuspension increased exposure. The versatility of the mill–autoclave–mill method was checked for 15 compounds, and the particle size of 12 compounds was in the nano range. The nanosuspension optimized in this study may be useful for intravenous toxicological and pharmacological studies in the early stage of drug development. Copyright © 2016 John Wiley & Sons, Ltd. Nanosuspensions for intravenous injections were prepared using a mixer mill and zirconia beads with a vehicle of 2% (w/v) poloxamer 338, which was confirmed to induce no histamine release in dogs. Sterilized nanosuspensions were obtained by milling for 30 min, followed by autoclaving for 20 min at 121 °C and milling for 30 min (mill–autoclave–mill method). The enhancing effect of a nanosuspension on exposure in dogs and the versatility of the method were demonstrated.