Impurities: Definition, Classification and Sources

 Impurities

An impurity in a drug substance as defined by the international conference on harmonization (ICH) guidelines is -any component of the drug substance that is not the chemical entity defined as the drug substance and affects the purity of active ingredient or drug substances.

An impurity in a drug product is any component of the drug that is not the chemical entity defined as the drug substance or an excipient in the drug product.

Common terms of impurities:

1. Intermediate penultimate intermediate andn byproducts

2. Transformation products

3. Interaction products 

4. Related products 

5. Degradation products 

 

Classification of impurities:

Impurities in drug substance can be classified into the following categories-

1. Organic impurities

2. Inorganic impurities 

3. Residual solvents

Sources of impurities:

1. Raw materials 

2. Method of manufacture 

3. Impurities due to storage condition 

                   a) Chemical instability 

                   b) Changes in the physical properties 

                   c) Reaction with container materials 

                   d) Temperature