The coding system for therapeutic equivalence evaluations allows users to determine whether FDA has evaluated a particular approved product as therapeutically equivalent to other pharmaceutically equivalent products (first letter) and to provide additional information on the basis of FDA's evaluations (second letter). Sample TE codes: AA, AB, BC.

• FDA assigns therapeutic equivalence codes to pharmaceutically equivalent drug products. A drug product is deemed to be therapeutically equivalent ("A" rated) only if:
• a drug company's approved application contains adequate scientific evidence establishing through in vivo and/or in vitro studies the bioequivalence of the product to a selected reference listed drug.
• those active ingredients or dosage forms for which no in vivo bioequivalence issue is known or suspected.
• Some drug products have more than one TE Code.
• Those products which the FDA does not deem to be therapeutically equivalent are "B" rated.