Preparation of some steroids in microcrystalline form by rapid freeze‐sublimation technique

Since it is sometimes desirable that insoluble therapeutic agents, such as steroids, in aqueous suspensions intended for parenteral use be present as extremely small particles, a procedure for acquiring powders in this state was investigated. A condensation method utilizing a rapid freezing-sublimation drying technique was found to be suitable for the preparation of cholesterol, pregnenolone, and -δ4-androstene-3,17-dione in the form of submicron particles. The average particle size of the powders obtained by this procedure was calculated from data by determining the specific surface area. Data are given to show that the average particle size obtained is influenced by the steroid chosen, the concentration of the steroid in the initial solution, the solvent used, the temperatures employed in the process, and the presence of certain additives.