ABSTRACT
SOLID FORMS AND THEIR CHARACTERISTICS An awareness of the properties of the solid form in which drug substances (APIs) are manufactured and isolated today plays an important role in pharmaceuticals development. In the majority of cases a crystalline form is preferred, which enables the substance to be produced reliably and reproducibly with well-defi ned and characterized physical properties. However, a recent trend in pharmaceuticals development is a move toward APIs that are more lipophilic, hydrophobic, and insoluble in nature (1), and in these cases limitations in bioavailability may favor the development of amorphous or metastable forms with higher solubilities and dissolution rates (2). Whatever solid form is chosen will provide the starting point for the formulation of the drug, and the formulation and means of delivery will conversely exert requirements and restrictions on the solid form selection (3). For example, an amorphous API is not desirable for administration via a conventional dry powder inhaler.
