The sponsor may have evidence that a related impurity present in the drug product is a previously
identified/qualified synthetic impurity. In this case, no further qualification for that impurity is required at the
drug product stage. The concentration reported for the established synthetic impurity may be excluded from
the calculation of the total degradation products in the drug product, and should be clearly indicated as such
in the drug product specifications. Evidence should be provided in the submission demonstrating the related
impurity is indeed a synthetic impurity (e.g., by showing constant levels during accelerated and/or shelf-life
stability studies and confirmation by providing chromatograms of spiked samples). In cases where the
methodology applied to the drug substance and drug product differs, the claim should be confirmed by
appropriate studies and the results submitted (e.g., using actual reference standards for that compound).
