FDA Inactive Ingredients Guide

According to the FDA, an inactive ingredient is merely an additive to help any active ingredients produce an effect on the human body. As such, the FDA does not monitor inactive ingredients during the production phase of drugs, or during clinical trials; instead, the FDA monitors the finished product and keeps record of any inactive ingredients through the Inactive Ingredients Database.

Inactive Ingredients Database

The FDA monitors inactive ingredients regularly; the Inactive Ingredients Database provides information of inactive ingredients already present in FDA-approved pharmaceuticals. The database serves as an educational resource that aids in future drug development. The Office of Generic Drugs is responsible for monitoring new drugs on the market and for chronicling any new inactive ingredients. In addition, if a specific inactive ingredient appears to be unavailable, you can contact the Office of Generic Drugs for more information. All inactive ingredients listed in the database possess a CAS RN as well as a UNII.

Office of Generic Drugs

7500 Standish Place

Rockville, MD 20855


Chemical Abstracts Service (CAS)

The American Chemical Society's division, known as CAS, remains a comprehensive source for chemical information. CAS Registry Numbers, or CAS RNs, are unique identifiers for chemical substances, such as inactive ingredients. The FDA uses these numbers in order to properly catalogue inactive ingredients within the Inactive Ingredient Database.

Chemical Abstracts Service

2540 Olentangy River Road

Columbus, OH 43202



Unique Ingredient Identifier (UNII)

Through collaborations with USP Substance Registration System (SRS), the FDA has created unique ingredient identifiers for substances in drugs, such as inactive ingredients. This UNII is a completely unique identifier based on a substance's molecular structure. The FDA uses it for product labeling, and the US government uses it in order to identify drug ingredients and food allergens within new drug products. Any query application for an inactive ingredient requires the UNII. You can obtain a UNII free of charge by contacting the FDA by email at SRS@cder.fda.gov.

Understanding the Database

Any inactive ingredient registered with the Inactive Ingredients Database contains six fields: the actual name of the inactive ingredient, the route and dosage form, the CAS number, the UNII, the maximum potency amount and the potency unit. The route is basically a description of how the drug is administered to a patient, whereas the dosage form describes the form in which the drug is produced, be it liquid, pill, capsule, etc. The maximum potency details the maximum amount of inactive ingredients per dosage. If the inactive ingredient is incalculable, then that field remains blank. By understanding such field descriptions, you can better understand any results found with the Inactive Ingredient Database.

FDA/Center for Drug Evaluation and Research

Office of Generic Drugs

Division of Labeling and Program Support


10903 New Hampshire Avenue

Silver Spring, MD 20993