The Formation of the solid form by the isolation or crystallization process (solvent, temperature, rate, concentration) will dictate the physical and chemical purity, as well as morphology and particle size. Knowledge from the solid form landscape can inform aspects of isolation and scale up so that batches are produced with consistent properties. Generation and analysis of physical characterization data on batches produced can yield useful insights into process variation such as solvent inclusion, morphology changes or solid form purity.
The impact of subsequent processing downstream from isolation such as drying and particle size reduction (milling) are also important to characterize. Secondary changes to form such as dehydration and amorphization can occur due to drying and milling for many materials and can result in process induced transformation. These subtle changes can have subsequent impact on how the drug substance behaves in the formulation process, affect chemical stability and alter the formulation’s performance characteristics. Experimentally based assessment of the formation process stresses on the drug substance form can be conducted to determine the risk of process induced transformation. Likewise, when micronization is conducted, thorough solid state characterization can build important understanding of the risks of comminution and mitigation strategies.