A Review of Formulation and Process Considerations for Achieving Stability in Solid Dispersions Produced via the Spray Drying Technique

Abstract

The poor water solubility of existing drugs and those in the pharmaceutical pipeline has persisted as a challenging issue for the industry over the past several decades. The development of amorphous solid dispersion (ASD) has gained considerable importance in recent years. ASD involves dispersing drug molecules in amorphous polymeric carriers, preventing crystallisation, and ultimately improving solubility. Spray drying, due to its ability to facilitate extremely quick solvent evaporation, stands out as an effective technology for the production of solid dispersions. The formation of ASDs is influenced not only by the kinetics of solvent evaporation but also by various other elements. The state in which the active pharmaceutical ingredient (API) is in solution, the interaction between the API, carrier, and solvent, formulation variables such as feed concentration or solvent type, and process parameters such as drying gas flow rate or solution spray rate are some examples of these. The final physical structure of the solid dispersion particles is influenced by all of these elements combined. ASD formulations that perform well and remain stable over the pharmaceutical product’s shelf life are mostly dependent on formulations, polymer selection, and spray-drying parameter settings. By addressing the instability challenges of ASD, the pharmaceutical industry could leverage the promise of ASD to overcome stability limitations and usher in a new era of enhanced drug delivery systems.

Keywords: Solid dispersion, Stability, Polymer, Solvent, Spray drying, Process control