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

– Undesired change in performance, i.e. dissolution/bioavailability

– Substantial changes in 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

-Particle size of 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 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.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 shelf life for the drug product.
  • Determine recommended storage conditions
  • Determine container and closure system suitability.
  • Safety point of view of 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 Mould 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 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 uo physical characteristics
  • Compatibility with common excipients
  • Formulating an elegant, safe, efficacious dosage form with good bioavailability.
  • To formulate 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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