Unique Ingredient Identifier

The UNique Ingredient Identifier (UNII) is a non-proprietary, free, unique and unambiguous identifier, non-semantic and alphanumeric linked to the molecular structure of a substance or descriptive information by the Registration System of the FDA Substance Registration System. A UNII is always ten characters in length, and is generated at random, so that it does not contain any information inherent in the time of entry or the type of substance.

SRS is used to generate permanent and unique identifiers for substances in regulated products, such as drug ingredients. The system uses molecular structure and descriptive information to define a substance and generate an UNII. The main means for the definition of a substance is by its molecular structure represented in a two-dimensional plane. When a molecular structure is not available (eg botanicals), UNII is defined from descriptive information.

The SRS procedure and management is provided by the SRS Board, which includes experts from the FDA and the United States Pharmacopeia (USP). Examples

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