Table 2

FDA Coding System for Therapeutic Equivalence for Drug Products

CodeDescription
ADrug products that the FDA considers to be therapeutically equivalent to other pharmaceutically equivalent products, that is, drugs for which:
  • There are no known or suspected bioequivalence problems. These are designated AA (conventional dosage forms), AN (solutions and powders for aerosolization), AO (injectable oil solutions), AP (injectable aqueous solutions), or AT (topical products)

  • Actual or potential bioequivalence problems have been resolved with adequate in vitro and/or in vivo evidence supporting bioequivalence. These are designated AB. Drugs coded as AB under a specific product heading are considered to be therapeutically equivalent only to other drugs coded as AB under that heading.

BDrug products that the FDA at this time considers not to be therapeutically equivalent to the other pharmaceutically equivalent products for which 1 of the following is true:
  • Actual or potential bioequivalence problems have not been resolved by adequate evidence of bioequivalence. Often the problem is with specific dosage forms rather than the active ingredients.

  • The quality standards are inadequate, or the FDA has had an insufficient basis to determine therapeutic equivalence.

  • The drug products are currently under regulatory review.


The subcodes consist of BC (extended-release capsules, injectables, tablets); BD (active ingredients and dosage forms with documented bioequivalence problems); BE (delayed release oral dosage forms); BN (aerosol-nebulizer drug delivery); BP (active ingredients and dosage forms with potential bioequivalence problems); BR (suppositories and enemas); BS (products having drug standard deficiencies); BT (topical products); BX (drug products with insufficient data); or B.

FDA indicates U.S. Food and Drug Administration.

Table content adapted from U.S. Food and Drug Administration (1).

  • A number is added to the end of the code (e.g., AB1, AB2), which indicates that >1 reference drug of the same strength has been designated under the same heading. Two or more reference medications are identified only when there are at least 2 potential reference drug products that are not bioequivalent to each other.

  • Code B represents drugs that may have been previously assigned an A or B code before new information raising significant questions about therapeutic equivalence was received by the FDA. The therapeutic equivalence of the product may be redetermined after the FDA completes its investigation and review.