2. CLASSIFICATION OF IMPURITIES

Organic impurities can arise during the manufacturing process and/or storage of the new drug substance .They are normally known and identified and include : Reagents,ligands and catalysts.Since these are generally of known toxicity , the selection of appropriate controls is easily accomplished ( see ICH Guideline Q3C on Residual Solvents ) .Excluded from this document are : extraneous contaminants that should not occur in new drug substances and are more appropriately addressed as Good Manufacturing Practice(GMP)issues, polymorphic forms, and ( 3 enantiomeric impurities .