Causes of Drugs Instability and their Preventation

 The Drug instability can be defined as the ability of the drug or formulation to remain in the fixed specification of identity and purity (i.e. chemical, physical, therapeutical, microbial, toxicological states, etc.) up to some specific period of time into a specific storage condition.

Causes of Instability and their Prevention

Common causes of instability and degradation are:

1. Hydrolysis
2. Oxidation
3. Photolysis

1. Hydrolysis

It is the breaking of molecule due to reaction with water.

Drugs which commonly hydrolysed are: Ester, Ether and Lactams.

    

A. Hydrolysis of Ester:

Examples: Procaine, Atropine, Aspirin, Physostigmine, etc.

Procaine

Atropine

Aspirin

Physostigmine

B. Hydrolysis of Amide:

Examples: Dibucaine, Ergometrine, Chloramphenicol, Barbiturates, etc.

C. Hydrolysis of lactams