Practical Considerations for Spray Dried Formulation and Process Development

Engineering Advances in Spray Drying for Pharmaceuticals

Spray drying is a versatile technology that has been applied widely in the chemical, food, and, most recently, pharmaceutical industries. This review focuses on engineering advances and the most significant applications of spray drying for pharmaceuticals. An in-depth view of the process and its use is provided for amorphous solid dispersions, a major, growing drug-delivery approach. Enhanced understanding of the relationship of spray-drying process parameters to final product quality attributes has made robust product development possible to address a wide range of pharmaceutical problem statements. Formulation and process optimization have leveraged the knowledge gained as the technology has matured, enabling improved process development from early feasibility screening through commercial applications. Spray drying's use for approved small-molecule oral products is highlighted, as are emerging applications specific to delivery of biologics and non-oral delivery of dry powders. Based on the changing landscape of the industry, significant future opportunities exist for pharmaceutical spray drying.

Combination of Colloidal Silicon Dioxide with Spray-Dried Solid Dispersion to Facilitate Discharge from an Agitated Dryer

A feasibility evaluation of the addition of fumed silica (SiO₂) into an agitated dryer to aid spray-dried solid dispersion intermediate (SDSDi) flow during secondary drying and discharge is described. The quantity of SiO₂ to enhance the flow character of SDSDi was assessed by measuring particle size distribution, bulk density, and flow-through-an-orifice. Results indicate that the addition of the SiO₂ did not alter the drying kinetics and did not impact the bulk particle size distribution of the SDSDi. While bulk density of SDSDi increased with the addition of SiO₂, the flow, and thus the recovery of the SDSDi-SiO₂ batch from the secondary dryer, was significantly higher than that for the intermediate alone. Imaging indicated uniform distribution of SiO₂ in the bulk powder and coating on intermediate particles. Premixing and co-sieving of the SiO₂ with a portion of pre-dry SDSDi promotes the uniform distribution of SiO₂ within the bulk powder bed.

Effects of the Preparation Process on the Properties of Amorphous Solid Dispersions

The use of amorphous solid dispersions to improve the bioavailability of active ingredients from the BCS II and IV classifications continues to gain interest in the pharmaceutical industry. Over the last decade, methods for generating amorphous solid dispersions have been well established in commercially available products and in the literature. However, the amorphous solid dispersions manufactured by different technologies differ in many aspects, primarily chemical stability, physical stability, and performance, both in vitro and in vivo. This review analyzes the impact of manufacturing methods on those properties of amorphous solid dispersions. For example, the chemical stability of drugs and polymers can be influenced by differences in the level of thermal exposure during fusion-based and solvent-based processes. The physical stability of amorphous content varies according to the thermal history, particle morphology, and nucleation process of amorphous solid dispersions produced by different methods. The in vitro and in vivo performance of amorphous formulations are also affected by differences in particle morphology and in the molecular interactions caused by the manufacturing method. Additionally, we describe the mechanism of manufacturing methods and the thermodynamic theories that relate to amorphous formulations.

New Strategies for Improving the Development and Performance of Amorphous Solid Dispersions

The understanding of amorphous solid dispersions has grown significantly in the past decade. This is evident from the number of approved commercial amorphous solid dispersion products. While amorphous formulation is considered an enabling technology, it has become the norm for formulating poorly soluble compounds. Despite this success, improvements can still be made that enable early development formulation decisions, to develop a rationale for selecting a manufacturing process, to overcome degradation and phase separation during processing, to help achieve physical stability during storage, and to optimize dissolution behavior. The purpose of this literature review is to present recently reported strategies for improving the development and performance of ASDs. The benefits and limitations of each strategy as well as recent relevant case studies will be presented in this review. The strategies are presented from three different aspects: (a) prediction techniques that enable formulation decisions, (b) manufacturing considerations that help produce physically and chemically stable ASDs, and