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
give
rise 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
are
normally known and identified as
reagents, ligands, inorganic salts, heavy metals, catalysts, filter aids and charcoal etc.
Sources of organic
impurities:
- Impurities
originating from drug
substance 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 the
drug 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.
Limit test is generally carried out to determine the inorganic impurities present in compound.