Physical Evaluation of Drugs

Definition

• Measurement of physical parameters and constants that help gauge purity and identity.

Common Physical Tests

1. Foreign Matter Content: Visual or sieve-based inspection.

2. Moisture Content / Loss on Drying: Prevents microbial growth, ensures stability.

3. Ash Values

   • Total Ash: Inorganic residue after incineration.

   • Acid-Insoluble Ash: Detects silica and dirt.

   • Water-Soluble Ash.

4. Extractive Values: Water-soluble, alcohol-soluble extractives indicating content of soluble constituents.

5. Volatile Oil Content: For aromatic drugs (clove, cinnamon).

6. Melting/Boiling Point: Helps identify purified natural compounds (e.g., camphor).

7. Specific Gravity / Optical Rotation: Characteristic for certain oils and solutions.

Significance

• Quantitative measure of purity (limits set in pharmacopoeias).

• Quality control benchmark across batches.

Limitations of Physical Evaluation of Drugs

• Does not definitively confirm chemical identity of active constituents.

• Some tests can vary based on environmental or processing factors.