File Entry: DEFINITION “IMPURITY”

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Impurities are normally generated during the formation of Active PharmaceuticalIngredients and their intermediates. Chances of their generation during Drug Productsformation are less as formulation is a physical blending process. Care is taken that theseexcipients do not react with each other to produce the degradants. They may consist oforganic and inorganic, and define levels at which impurities/degradants should beidentified.ICH Q3A covers drug substances and Q3B covers drug products. These guidelines definewhat investigations and documentation should be made in investigating impurities anddegradation products seen in stability studies at recommended storage conditions. Basedon the data generated their specification can be arrived at. Depending on their amount thequalification, if required is carried out.Impurity synthesis involves three steps: Detection, Modes of Formation, Synthesis andStructure elucidation by using various techniques. Determination of Purity of Impurity ismandatory otherwise its quantification in the API and Drug products can be challenged.