The first letter in the orange book rating code indicates?

What does the first letter in the Orange Book rating code mean?

In the FDA’s Orange Book rating code, the first letter indicates the drug product’s therapeutic equivalence category—specifically whether the product is considered therapeutically equivalent to a listed reference listed drug (RLD).

How are the Orange Book therapeutic equivalence letters interpreted?

The common letter used in practice is:

- A: The active ingredient in the applicant’s drug product is considered therapeutically equivalent to the RLD (i.e., the generic can be substituted for the brand under the FDA’s therapeutic equivalence framework).

What about other letters you might see?

Other letters correspond to products that are not rated as therapeutically equivalent in the same way as category A (for example, when the product is not rated as therapeutically equivalent or when additional data are needed). The specific letter-to-meaning mapping depends on the exact Orange Book code shown.

If you paste the exact code, I can tell you the meaning of that first letter

If you share the full Orange Book rating code (or the letter and the product it appears next to), I can translate the first letter in that specific context.

Sources

1. FDA Orange Book – Therapeutic Equivalence Evaluations (general information)