Study of Physicochemical Characteristics of Drug Substances

• Understanding the Physicochemical Characteristics 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:

1. Physical Properties:

   • Physical form (crystalline vs. amorphous)
   • Particle size and shape
   • Flow properties

2. Chemical Properties:

   • Solubility and dissolution rate
   • pKa (acid dissociation constant)
   • Partition coefficient (log P)
   • Stability and degradation pathways

3. Thermal Properties:

   • Melting point
   • Glass transition temperature

4. Spectroscopic Properties:

   • Infrared (IR) spectroscopy
   • Nuclear Magnetic Resonance (NMR)
   • Ultraviolet-visible (UV-Vis) spectroscopy

5. Polymorphism:

   • Different crystalline forms of the same drug substance.

Importance of Physicochemical Characteristics of Drug:

• 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.

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