What Orange Book designation indicates that there are no bioequivalence problems?

The designation that indicates there are no bioequivalence problems is denoted by the letter A in the Orange Book. The Orange Book, officially known as the "Approved Drug Products with Therapeutic Equivalence Evaluations," is published by the FDA and provides a system for classifying drugs based on their therapeutic equivalence.

When a drug product is classified with an A designation, it signifies that the product is considered therapeutically equivalent to other drug products and that there are no known or suspected bioequivalence issues. This means that the A-rated products can be substituted for each other without concern for variance in efficacy or safety in the clinical settings.

In contrast, a B designation indicates that a drug product may not be therapeutically equivalent due to bioequivalence problems, and it may not be safe to substitute it with products labeled A without the need for further evaluation. The BX designation is used specifically for products with unresolved bioequivalence issues, making it less favorable for substitution. The designation "O" is not part of the therapeutic equivalence classifications related to bioequivalence.

Thus, the letter A clearly conveys that the referenced product does not have any bioequivalence concerns, making it a safe choice for substitution in therapy.