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Substance Registration System – UNII Presentation

Substance Registration System – UNII Presentation

Presentation: March 20, 2007 

William A. Hess, CAPT 

Food and Drug Administration


SRS/UNII Purpose


The overall purpose of the joint FDA/USP Substance Registration System (SRS) is to support health information technology initiatives by providing unique ingredient identifiers (UNII) for substances in drugs, biologics, foods, and devices based on molecular structure and/or descriptive information.


  • The SRS is used to generate permanent, unique, unambiguous identifiers for substances in regulated products, such as ingredients in drug products. 
  • The SRS's non-proprietary Unique Ingredient Identifiers (UNIIs) are designed to be free for use in health information technology systems. 
  • Current substance identifiers used elsewhere in the federal government and in the private sector lack one or more of the characteristics important for supporting many of the health information technology initiatives. 
  • The UNII is one of the core components of the United States Federal Medication Terminology. 
  • The UNII is part of the FDA's Structured Product Labeling http://www.fda.gov/oc/datacouncil/spl.html, and can be used to generate other medication terminologies including the National Library of Medicine's (NLM's) RxNorm http://www.ncvhs.hhs.gov/060913lt.htm. SPL and the UNII will be made available in the DailyMed http://dailymed.nlm.nih.gov/dailymed/about.cfm, which is a medication information repository maintained by NLM. 
  • The UNII has been adopted by the United States Consolidated Health Informatics initiative http://www.hhs.gov/healthit/chiinitiative.html; http://www.hhs.gov/healthit/documents/chiinitiative/med_ingred_full_public.pdf 
  • The UNII is recommended by the National Committee on Vital and Health Statistics http://ncvhs.hhs.gov/031105lt2.pdf at page 8 UNIIs have been incorporated into the VA's National Drug File Reference Terminology (NDF-RT), which in turn is available through NLM's Unified Medical Language System (UMLS) http://www.nlm.nih.gov/research/umls/metab2.html
  • UNIIs have been incorporated into the National Cancer Institutes Enterprise Vocabulary Service http://www.cancer.gov/cancertopics/terminologyresources/page5 
  • UNIIs will be incorporated into the electronic version of the 2007 edition of the USP Dictionary of USAN and International Drug Names http:// www.usp.org/products/dictionary/, as well as subsequent printed versions. 
  • UNIIs will be assigned to each substance that is in the Environmental Protection Agency's Substance Registry System http://www.epa.gov/srs/index.htm. 
  • UNIIs are available through several of the above referenced websites, and are available through FDA's website http://www.fda.gov/oc/datacouncil/UNIIs.zip



SRS/UNII Design 


  • The SRS uses molecular structure and descriptive information to define a substance and generate the UNII. 
  • The primary means for defining a substance is by its molecular structure represented on a two-dimensional plane. 
  • When a molecular structure is not available (e.g., botanicals), the UNII is defined by descriptive information. 
  • When a molecular structure alone is insufficient (e.g., polymers), the UNII is also defined by descriptive information. 
  • The UNII consists of ten alphanumeric characters. 
  • The first nine alphanumeric characters are randomly generated. 
  • The tenth alphanumeric character is determined through a mathematical algorithm, and is appended to the first nine.




  • Substances that are registered in the SRS follow detailed business rules for that registration which were developed by the SRS Project Management Team. 
  • In addition, substances that are registered in the SRS follow a detailed and robust set of data rules that were developed by the SRS Board for drawing molecular structures and representing descriptive information. 
  • The SRS Board consists of experts from both the USP and FDA, and it works very closely with drug regulators from other nations in the development of these rules.




  • Foods 
    • Food substances are specific foods or components of food, regardless of whether the food is in conventional food form or a dietary supplement, such as vitamins, minerals, herbs, or other similar nutritional substances. 
  • Drugs 
    • Drug substances include both active and inactive ingredients used in drug products, including those for veterinary purposes. 
  • Biologics 
    • Biologic substances include both active and inactive ingredients used in biologics, such as blood products, therapeutic products, vaccines, cellular and gene therapy products, allergenic products, tissues, and certain devices (e.g., enzymes in stabilized solutions). 
  • Devices 
    • Device substances include certain components of some devices (e.g. silicon for implants, and chemical reagents for glucose test kits). 
  • Cosmetics 
    • Cosmetic substances are components of cosmetic products, such as flavors, fragrances, colorants, vitamins, plant- and animal-derived ingredients, and polymers.


SRS/UNII Questions


Questions about the UNII should be directed to: 

CAPT William A. Hess