stability study of drugs

Stability study of drugs in Pharmaceutical Chemistry

Stability study of drugs

Stability of pharmaceutical product may be defined as the capability of a particular formulation in a specific container/closure system to remain within its physical, chemical, microbiological, therapeutic and toxicological specification.

Instability may cause

  • An undesired change in performance, i.e. dissolution/bioavailability
  • Substantial changes in the physical appearance of the dosage form
  • Causing product failures

Factors affecting Stability

1- Environmental factors

  • Temperature
  • Light
  • Oxygen
  • Moisture
  • Carbon dioxide

2- Drugs or excipients in the dosage form

  • The particle size of a drug
  • pH of the vehicle

3- Microbial contamination

4- Trace Metal Contamination

5- Leaching from containers

Stability Study

Stability testing/study is termed as a complex process because of the involvement of a variety of factors including

  1. stability of the active ingredients
  2. container/closure system used for packaging
  3. heat and moisture conditions encountered during shipment, storage, and handling.
  4. type of dosage form
  5. an interaction between active ingredients and excipients

Need for Stability Study

  • Provide evidence as to how the quality of the drug product varies with time.
  • Establish half-life for the drug product.
  • Determine recommended storage conditions
  • Determine container and closure system suitability.
  • Safety point of view of the patient.

 Types of Stability


Pharmaceutical Degradation

  1. Physical degradation
  2. Chemical degradation
  3. Microbiological degradation

Microbiological stability

Microbiological stability implies that:

The formulation has not suffered from any microbiological attack and is meeting the standards with respect to lack of contamination/sterility.

Sources of Microbial Contamination:

Water gram-negative groups: Pseudomonas,
Xanthamonas, Flavobacterium
Air Mold spores: Penicillium, Aspergillus
Bacterial spores: Bacillus spp. Yeasts
Raw materials Micrococci
Starches Coliforms
Pigments Salmonella
Gums Actinomyces
Animal products Salmonella, Coliforms
Personnel Coliforms, Staphylococci, Sterptococci


Preformulation is a branch of pharmaceutical science that investigate physico-chemical properties of new drug compounds in order to develop safe, effective, and stable dosage form.

Goals of  Preformulation

  • To develop the necessary physicochemical parameters of new drug substances.
  • Determining the kinetic rate profile.
  • To set up physical characteristics
  • Compatibility with common excipients
  • Formulating an elegant, safe, efficacious dosage form with good bioavailability.
  • To formulate a new dosage form of already existing drug.

Some commonly evaluated parameters

  • Crystallinity & Polymorphism
  • Hygroscopicity
  • Particle size & shape and
  • Bulk density
  • Surface area and Solubility
  • Stability

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