Study of Physicochemical Characteristics
Understanding the physicochemical properties of drug substances is paramount in pre-formulation studies.
These characteristics influence the drug's behavior during formulation, processing, and storage, as well as its bioavailability and therapeutic performance.
Key Physicochemical Characteristics:
Physical Properties:
Physical form (crystalline vs. amorphous)
Particle size and shape
Flow properties
Chemical Properties:
Solubility and dissolution rate
pKa (acid dissociation constant)
Partition coefficient (log P)
Stability and degradation pathways
Thermal Properties:
Melting point
Glass transition temperature
Spectroscopic Properties:
Infrared (IR) spectroscopy
Nuclear Magnetic Resonance (NMR)
Ultraviolet-visible (UV-Vis) spectroscopy
Polymorphism:
Different crystalline forms of the same drug substance.
Importance:
Formulation Design: Physicochemical properties determine the choice of dosage forms (e.g., tablets, capsules, injectables) and the selection of excipients.
Manufacturability: Properties like flowability and compressibility affect manufacturing processes such as tableting and encapsulation.
Stability: Understanding how the drug reacts to environmental factors ensures the formulation remains effective over its shelf life.
Bioavailability: Solubility and dissolution rates influence how the drug is absorbed in the body.