Interchangeability
Can one product be substituted for another at the counter? Compare two NDCs, or read the plain-English decoder below.
ⓘ How this was built
- FDA Orange Book therapeutic-equivalence (TE) codes
- FDA Purple Book interchangeability status
Two products are compared by their FDA-assigned TE code (Orange Book) or interchangeability status (Purple Book); the decoder restates FDA's own code definitions.
Pipeline and calculations built by Claude (Fable 5) from the public datasets above. Educational only — verify against primary sources before acting.
Compare two NDCs
Informational only, based on the latest FDA Orange Book, Purple Book, and NDC Directory data loaded here. Substitution rules vary by state, and ratings change — verify in the current Orange Book before dispensing. Not clinical advice.
The Orange Book codes, decoded
Every FDA-approved multi-source drug gets a two-or-three character therapeutic equivalence (TE) code. Only the first letter answers the substitution question: A means yes, B means no. Everything after it is context.
| Code | What it means at the counter |
|---|---|
| AA / AN / AO / AP / AT | A-rated, no known equivalence problems. The letter after A just describes the dosage form (AN aerosols, AO injectable oil, AP injectable aqueous, AT topical). Substitutable. |
| AB | A-rated after bioequivalence studies — the most common code on generics. Substitutable with other AB products of the same drug, strength, and form. |
| AB1, AB2, AB3… | The trap: numbers mean this drug has more than one reference product. AB1 products are only equivalent to other AB1s — an AB1 and an AB2 of the very same drug and strength are NOT substitutable. |
| B* / BC / BD / BE / BN / BP / BR / BS / BT / BX | B-rated: FDA has NOT shown therapeutic equivalence (documented or potential bioequivalence problems, or data under review — BX). Not substitutable. |
Two products must also be pharmaceutical equivalentsbefore the code matters at all: same active ingredient, same strength, same dosage form, same route. A 10 mg tablet is never substitutable for a 20 mg tablet, whatever the codes say.
Biologics work differently (Purple Book)
Biologics have no TE codes. A biosimilar is highly similar to its reference product but may not be substituted at the pharmacy — prescriber involvement is required. An interchangeable biosimilar carries an extra FDA designation that permits pharmacy-level substitution for its reference product, subject to state law. Two things trip people up: the designation only runs against the reference product (two biosimilars of Humira are never substitutable for each other), and the four-letter suffixes matter — adalimumab-adbm and adalimumab-afzb are different products.