Drug products with which of the following codes may be substituted for one another?

The correct choice is based on the significance of the code "AB" in relation to drug substitution. The "AB" code in the FDA's Orange Book designates that the drug products are considered therapeutically equivalent. This means that they can be substituted for one another without a risk of differing in efficacy or safety when used as intended.

Therapeutic equivalence ensures that the active ingredients, dosage form, route of administration, and strength are the same or therapeutically equivalent, allowing for confident substitution by pharmacists or healthcare providers. This is crucial for maintaining consistency in patient care and adhering to regulatory standards.

In contrast, other codes like "BZ," "CX," and "A" do not convey the same equivalence. For instance, "A" generally indicates that a drug product is rated as therapeutically equivalent to another product, but it can also specifically refer to those that do not require further evidence of equivalency to support substitution. "BZ" and "CX" would generally indicate potential issues with bioequivalence or other concerns that prevent automatic substitution.

Thus, the identification of "AB" as the code for therapeutic equivalence makes it the correct answer for drug products that can be substituted for one another confidently.