Control of degradants on stability

It is expected that the potency, purity, and quality of the drug substance be maintained over time. The chemical, physical, enzymatic, and microbiological quality, as appropriate, should be retained through to the claimed life of the drug substance and also through the life of the formulated drug substance, that is, the marketed drug product. 

For drug substances, a retest date is generally determined. The period up to the retest date is a period during which the material is known to adhere to its specification, for example, for assay or degradants. The retest date may be assigned on the basis of real-time stability data obtained at the recommended storage conditions or on the basis of accelerated stability data obtained under more stressful conditions. 

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