Final answer:
A generic drug must be therapeutically equivalent to its brand-name counterpart to be substitutable, as per FDA requirements.
Step-by-step explanation:
In order for a generic drug to be substituted for a name brand drug, it must be considered therapeutically equivalent. The U.S. Food and Drug Administration (FDA) requires that a generic drug must provide the same clinical benefit and be as safe as the brand-name drug that it intends to duplicate. This ensures that the generic version can be interchangeable with its brand-name counterpart. A process known as an Abbreviated New Drug Application (ANDA) is used by the FDA to evaluate and approve generic drugs for therapeutic equivalence.