Bioavailability preformulation studies

Although they are often categorized as inert, preformulation studies can determine the inhuence of excipients on stability, bioavailability, and processability. Excipients are categorized into groups according to their main function, although some may be multifunctional, and examples of common excipients used in the manufacture of tablets and capsule are detailed in Table 3. 

Preformulation studies including interaction, challenge (similar (1) above), dissolution studies, polymorphic form, release, bioavailability, etc. 

Early on in product development, the potential for the successful development of a solid oral dosage form is assessed, based on the physicochemical properties of the API (1). Prior to solid dosage form development, it is necessary to anticipate the physicochemical properties that can have a major influence on product manufacture and performance. The early development (preformulation and early formulation development) studies should focus on these properties so as to avoid problems at later stages of development. While the molecular properties dictate the intrinsic solubility and the chemical stability of the compound, by controlling the physical form of the compound and by modifying physical properties (e.g., particle size), the dissolution rate can be enhanced with the potential for improving bioavailability. This chapter will focus on physical properties including particle characteristics, and most importantly, the physical form (i.e., solid state) of the API. 

Additional preformulation and physicochemical characterization of the candidate compound are performed and stress stability studies may be initiated. Ideally, the optimal solid state (polymorphic) and chemical (salt) form of the molecule are identified as part of clinical candidate selection. Selection of the most stable and bioavailable form will expedite subsequent development. The methods for testing the drug substance are refined and additional methods may be developed. 

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