Standardization of Drugs


Standardization of drugs may be defined as the achievement of uniform amount of active drug and uniform pharmacological activity in different pharmaceutical preparations of the same drug in accordance with the standards laid down in pharmacopoeia.


Assay is the estimation of the pharmacological activity in a unit quantity of preparation. There are different types of assay:

  • Chemical assay
  • Immunological assay
  • Biological assay (Bioassay)

Biological assays are indicated when:

  • Chemical assay is not available or not possible
  • Chemical composition of the drug is not known
  • Drug to be assayed is not in pure form (isolated form)

Disadvantages of bioassay include:

  • It is not very accurate
  • It is not easy to perform
  • Time consuming
  • Not cost-effective

Principles of Bioassay

  • Comparison with a standard
  • Response selected is close to the therapeutic or desired effect
  • Experimental conditions must remain constant
  • Statistical analysis is applied

Methods of Bioassay

  • Matching dose assay
  • 3-point assay
  • 4-point assay
  • Quantal assay

International Unit

A unit denotes a specific amount of pharmacological activity contained in a specific quantity of standard drugs. e.g.,

Insulin Unit

01 Unit: Amount of insulin required to decrease blood glucose levels from 120mg to 45 mg/dl in a 2Kg normal rabbit.

Heparin Unit

01 Unit: Amount of Heparin that prevents clotting of 1 ml of citrated sheep plasma for 1 hour after addition of 0.2 ml of 1:100 CaCl2 solution.

Biologically Standardized Drugs


  • Insulin
  • Oxytocin
  • Corticotrophin
  • Gonadotrophins

Immunological Products

  • Vaccines
  • Antitoxins
  • Antisera


  • Penicillin
  • Tetracycline
  • Streptomycin

Blood and Related Products

  • Factor VIII, IX
  • Protamine sulphate


  • Chymotrypsin
  • Hyalusonidase


Vitamin D

Next articleRoutes of Administration of Drugs
The writer enjoys medical education and has special interest in community medicine.