Effective polymeric dispersants for vacuum, convection and freeze drying of drug nanosuspensions

Drying nanosuspensions into redispersable powders is a critical issue in developing solid dosage forms of drug nanoparticles. The particle fusion and chain entanglement of polymeric steric stabilizers adsorbed onto the nanoparticle surface should be prevented to retain redispersibility after drying. Herein, we report that only a small amount of polymeric dispersants such as carrageenan, gelatin, and alginic acid between 0.5 and 3 wt.% in various drug nanosuspensions can provide sufficient redispersibility in vacuum, convection, and freeze drying. In vacuum and freeze drying of naproxen nanosuspensions, the addition of only 0.5 wt.% carrageenan resulted in the formation of redispersable nanoparticulate powders. The amounts of polymeric dispersants required for redispersibility was lowest for carrageenan and highest for gelatin. The specific interactions between the dispersants and steric stabilizers (or drugs), in addition to viscosity increase during drying, appeared to effectively prevent irreversible particle aggregation.