Sources of Impurities in Medicinal agent

The origin of impurities in drugs is from various sources and phases of the synthetic process and preparation of pharmaceutical dosage forms.

Majority of the impurities are characteristics of the synthetic route of the manufacturing process.

There are several possibilities of synthesizing a drug; it is possible that the same product of different sources may giverise to different impurities.

Organic impurities

may arise from starting materials, by products, synthetic intermediates and degradation products.

Inorganic impurities may be derived from the manufacturing process and arenormally known and identified as reagents, ligands, inorganic salts, heavy metals, catalysts, filter aids and charcoal etc.

Sources of organic impurities:

Impurities originating from drugsubstance synthetic processes
Starting materials and intermediates
Impurities in the starting materials
Reagents, ligands and catalysts
By-products of the synthesis
Products of over-reaction
Products of side reactions
Impurities originating from degradation of thedrug substance.

Limit Test

Limit test is defined as quantitative or semi quantitative test designed to identify and control small quantities of impurity which is likely to be present in the substance.