Q.01

How do I use the FDA inactive ingredient database?

The FDA Inactive Ingredient Database (IID) lists the excipients used in the final dosage forms of FDA-approved drugs. For each excipient it gives the route of administration, the dosage form and the highest amount approved so far. You use it to show that your excipient, at your level, has already been used in an approved product with the same route and dosage form. FDA says that once an excipient has appeared in an approved product for a particular route, it is "not considered new and may require a less extensive review" the next time.

How to use it

  1. Searching online. Use FDA's search page at accessdata.fda.gov/scripts/cder/iig/index.cfm and enter at least three characters of the ingredient name. Results are sorted alphabetically by ingredient, then by route, then by dosage form (FAQ).
  2. Matching on route and dosage form. Both come from the current approved labeling. FDA's controlled terms for them are in its Data Standards Manual (field descriptions). A precedent for one route or dosage form does not carry over to another.
  3. Reading the amounts:
    • Maximum potency is "the highest unit dose amount of the excipient used in approved products" for that dosage form. For topical products it is a percentage of the formula. It goes up when FDA approves a product with a higher level.
    • Maximum Daily Exposure (MDE) is calculated as excipient (mg) × number of units, at the maximum recommended daily dose. For oral products it is also called maximum daily intake (MDI). Your formulation is compared against both the per-unit-dose amount and the daily exposure (FAQ).
  4. Identifying the substance by code. Use the CAS number and the UNII (from the joint USP/FDA Substance Registration System) to pin down the exact excipient and cross-search other databases. The amount and unit fields "may be blank" where the value can't be calculated (field descriptions).
  5. Downloading for bulk or trend work. The file comes as comma-delimited text and Excel, under 2 MB unzipped, with seven fields: Inactive Ingredient, Route, Dosage Form, CAS Number, UNII, Potency Amount and Potency Unit. FDA updates it each quarter (by the tenth working day of January, April, July and October). The latest version is October 2026, and past text files go back to 2009, so you can track how an entry changed over time (download page).

What it doesn't tell you

  • It covers only ingredients the manufacturer named as inactive.
  • It does not cover contaminants.
  • It covers only final dosage forms of approved products.

FDA guidance

  • FDA's guidance Using the Inactive Ingredient Database is still a draft. It was issued in July 2019 (docket FDA-2019-D-2397) and its recommendations are non-binding.
  • It covers how the IID bears on excipient safety at filing and during scientific review, plus the database's structure, naming, maximum potency levels and units (guidance page).
  • I couldn't open the guidance PDF itself (fda.gov/media/128687/download), so the detail above comes from FDA's FAQ and field-description pages.

Approach: The IID isn't in the datasets I can search, so I used FDA's own IID pages: the FAQ, the field descriptions, the download page and the guidance landing page.

If you send an excipient name, route and dosage form, I can look up the current IID entry from FDA's site.

Q.02

Does an ingredient listing mean the FDA approved my formulation?

No. An IID listing does not mean FDA approved your formulation. FDA approves a specific drug product through its application. Under the generic-drug rules in 21 CFR Part 314, you still have to justify every inactive ingredient in your own product, and FDA can refuse approval on excipient grounds even if each ingredient appears somewhere in an approved product.

What the regulations require

  • You must provide your own justification. In an ANDA, "an applicant must identify and characterize the inactive ingredients in the proposed drug product and provide information demonstrating that such inactive ingredients do not affect the safety or efficacy of the proposed drug product" (§ 314.94(a)(9)(ii)) [1].

  • FDA judges the whole formulation, not single ingredients. FDA "will refuse to approve" an ANDA if the inactive ingredients are unsafe, or if "the composition of the drug product is unsafe... because of the type or quantity of inactive ingredients included or the manner in which the inactive ingredients are included" (§ 314.127(a)(8)) [2]. A combination or level of excipients can fail even when each excipient is listed.

  • Some changes "may raise serious questions of safety or efficacy." The examples FDA lists include [2]:

    • an inactive ingredient not previously approved for human use by the same route of administration;
    • for parenteral and ophthalmic products, an ingredient not previously approved in a product for that use;
    • "a significantly greater content of one or more inactive ingredients than previously used in the drug product."

    This is why the route of administration and the maximum amount in the IID matter. A listing for a different route, or for a lower amount, does not support your use.

  • Some products must match the reference drug's excipients. This applies whatever the IID shows:

    • Parenteral products must generally contain the same inactive ingredients in the same concentration as the reference listed drug. Only preservatives, buffers and antioxidants may differ, and only with supporting data (§ 314.94(a)(9)(iii)) [1].
    • Ophthalmic and otic products follow the same rule. Only preservatives, buffers, tonicity agents and thickeners may differ, and an ophthalmic product may not change a buffer or tonicity agent to claim a therapeutic advantage (§ 314.94(a)(9)(iv)) [1].
    • Topical products, solutions for aerosolization or nebulization, and nasal solutions "shall contain the same inactive ingredients" as the reference listed drug, unless the differences are characterized and shown not to affect safety or efficacy (§ 314.94(a)(9)(v)) [1].

How to use an IID listing. Treat it as evidence that an excipient has been used before, for a given route and dosage form, up to a given amount. You cite it in your application to support your excipient choice and level. Approval comes only when FDA approves your application for your specific product.

Approach: I searched FDA's application and approval regulations in 21 CFR Part 314 (current eCFR text). The quoted rules are the ones for ANDAs (generic applications); I didn't pull the equivalent NDA provisions.

Q.03