Background:  PQ/CMC has a requirement to capture drug product impurities.  These impurities are substances.

Request adding a new element called impurity to MedicialProductDefinition

Element name: impurity  (0..*)  References SubstanceDefinition Resource

Definition:  Any component of the drug product which is not the chemical entity defined as the drug substance or an excipient in the drug product. This includes process-related impurities and contaminants, product-related impurities including degradation products. [Source: Adapted from ICH Q6A and ICH Q6B ]