Final answer:
An approved drug may become a new drug if made by a different manufacturer, uses different excipients or inactive ingredients, is used for a different purpose, or undergoes a substantial change.
Step-by-step explanation:
An approved drug may become a new drug in several instances. One example is when it is manufactured by a different manufacturer which could involve changes to the production process or quality controls. Another instance is when there is a change in the excipients or inactive ingredients that could affect the drug's stability, absorption, or overall effectiveness.
A third instance is when the drug is used for a different purpose, meaning it has a new indication or therapeutic use that requires additional approval. Lastly, a drug can be considered new if it undergoes a substantial change in formulation, dosage, or method of administration that could impact its safety and efficacy profiles.
Before a new drug can be marketed, it must be thoroughly evaluated and approved through a New Drug Application (NDA) by the FDA's Center for Drug Evaluation and Research (CDER), following significant testing in clinical trials for safety and effectiveness. Even after approval, continued monitoring through pharmacovigilance systems is critical to assess long-term safety and the impact on specific patient subgroups.