FDA inactive ingredient database search and interpretation
Search the FDA inactive ingredient database for excipient precedent. Check route, dosage form and potency without treating a listing as FDA approval.
The FDA inactive ingredient database (IID) records inactive ingredients used in the final dosage forms of FDA-approved drugs. Search the IID database by ingredient name, then compare the route, dosage form, listed amount and unit with your proposed use. An entry provides evidence of previous approved use, not approval of your formulation. FDA explains these limits in its IID FAQ.
Use the official IID search for a lookup. If that application is unavailable, use FDA's Inactive Ingredients Database download in text or Excel.
What an IID entry means
IID covers final dosage forms, not contaminants. An ingredient's role also matters: the same substance can be active in one formulation and inactive in another. The FDA IID FAQ says prior approved use for a particular route may mean the ingredient is no longer considered new for that purpose and may require a less extensive review, but that does not establish suitability for every formulation or exposure.
Treat a matching entry as a starting point. A listing for another route or dosage form does not establish equivalent precedent. It calls for an appropriate assessment rather than an assumption that the proposed use is either permitted or prohibited.
How to search the inactive ingredient database
Start with an ingredient name
Enter at least three characters from any part of the ingredient name. FDA describes results as alphabetical by ingredient, then route and dosage form. The routes and dosage forms come from current approved labeling. The FDA FAQ gives these search steps.
Check the substance identity before comparing amounts. CAS numbers and Unique Ingredient Identifiers (UNIIs) help identify the ingredient, but neither proves approval. Not every inactive ingredient has a UNII, so a missing identifier does not settle the assessment. FDA explains missing values in its IID FAQ.
Match the route and dosage form
Read the route and dosage form alongside the ingredient name. Do not select the largest amount across all entries and apply it to your formulation.
Record the amount together with its unit. FDA distinguishes unit-dose amounts from percentages used for topical and other percentage-based formulations. The FDA FAQ defines both.
Use the download when needed
FDA offers comma-delimited text and Excel files. Its download page documents seven columns: Inactive Ingredient, Route, Dosage Form, CAS Number, UNII, Potency Amount, and Potency Unit. Use those fields to keep identity, route and amount together in your review.
FDA says potency can show NA when there is no calculable measurement. NA is not zero. Do not treat it as unlimited use either. The FAQ also explains N/A entries for identifiers.
Read maximum potency separately from daily exposure
FDA defines maximum potency as the highest unit-dose excipient amount in approved products behind an entry. For topical and other percentage-based formulations, it means the highest formula percentage. Maximum daily exposure (MDE) is the total excipient amount used in a day based on the maximum daily dose, per FDA's definitions.
| Measure | What to compare |
|---|---|
| Maximum potency | The amount per dosage unit, or formula percentage, for the relevant entry |
| Maximum daily exposure | Total daily excipient exposure based on the maximum daily dose |
For a specified product, multiply the excipient amount per dosage unit by the maximum recommended units per day. That calculates that product's daily exposure. Oral MDE may also be called maximum daily intake (MDI), according to the FDA FAQ.
But don't calculate an authoritative IID MDE by multiplying a listed potency by an assumed dosing schedule. FDA says potency and MDE can come from different approved applications. Do not assume an MDE replacement is a multiple of the potency it replaced. FDA is adding MDE values in phases, so do not expect one in every record. The quarterly change log explains the replacement rule. Neither measure is automatic permission for a proposed use.
Check the release and record changes
FDA describes quarterly IID updates in January, April, July and October. The change log lists an October 2026 publication. The download page is current as of October 19, 2026, and the previous file it lists is July 2026. As a practical recordkeeping step, save the source, release details and entry used for your assessment.
The change log is not a complete list of additions, which is easy to miss if you only open that file. FDA says new records and increases appear in the primary IID display with "Y" in Updated Record. A deletion can reflect a route or dosage-form correction, rather than removal of the excipient as a whole. Check the change-log explanation before drawing conclusions from a changed row.
IID and the NDC Directory answer different questions
An NDC listing alone establishes neither approval nor IID precedent. The NDC Directory contains labeler-submitted listings for approved and unapproved products. FDA says inclusion does not mean it has verified the data or approved the product. Assignment of an NDC does not denote approval either. These limits appear on the NDC Directory page.
Do not assume that an NDC listing automatically populates IID. FDA describes IID potency and MDE as coming from approved applications in its change-log explanation. Use the IID entry itself when assessing excipient precedent.
RegAffairs AI's answer on the inactive ingredient database covers the lookup and why a listing does not approve a formulation.