What is the difference between active ingredient and generic name? Is generic name always equal to the active ingredients or are these sometimes different?

For example, Benadryl has a generic name, according to RXList, of diphenhydramine. Basically, RXList, drugs.com, and other sites call diphenhydramine the generic name, while the FDA API calls diphenhydramine the active ingredient.

So are these two terms synonyms?

1 Answer 1


The FDA API data dictionary defines active_ingredient as:

A list of the active, medicinal ingredients in the drug product.

The FDA also has a helpful glossary:

Active Ingredient
An active ingredient is any component that provides pharmacological activity or other direct effect in the diagnosis, cure, mitigation, treatment, or prevention of disease, or to affect the structure or any function of the body of man or animals.

In contrast the data dictionary defines generic_name as:

Generic name(s) of the drug product.

The glossary notes:

Generic Drug
A generic drug is the same as a brand name drug in dosage, safety, strength, how it is taken, quality, performance, and intended use. Before approving a generic drug product, FDA requires many rigorous tests and procedures to assure that the generic drug can be substituted for the brand name drug. The FDA bases evaluations of substitutability, or "therapeutic equivalence," of generic drugs on scientific evaluations. By law, a generic drug product must contain the identical amounts of the same active ingredient(s) as the brand name product. Drug products evaluated as "therapeutically equivalent" can be expected to have equal effect and no difference when substituted for the brand name product.

The difference is easily apparent when you consider one of the many combination drugs. These are two or more active ingredients in one.

For example, consider Hyzaar. This brand-name drug is an attempt by a drug company to market a combination of two generically available drugs and jack up the price (Sacks et al 2018. PMCID PMC6142946). The API lists the generic name as:


While the active ingredients are listed in an array:

  "strength": "12.5MG"
  "strength": "50MG"

Consider the API results for Zegerid, which is a combination of omeprazole and sodium bicarbonate. The active ingredients list both, but there is in fact no generic listed, probably because there is no other company trying to market omeprazole together with Tums.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.