Observational Health Data Sciences and Informatics

NDC (National Drug Codes) is a coding system used for drugs commercially available in the US. NDC consist of three components:

1. manufacturer number (up to 5 digits)
2. product code (up to 4 digits)
3. packaging information (up to 2 digits)

The FDA assigns the manufacturer number to each manufacturer. Manufacturers can be an organizations that actually manufacture the drug, or resellers or distributors. Each manufacturer is responsible for encoding the product and packaging information. This system is not strictly enforced, which means that NDC codes with the same manufacturer number and product code do not always designate the same product. It also means that NDC codes can be repeated over time designating different products, though this happens very rarely.

There is no one comprehensive repository of all NDC codes available. Instead, the FDA, the NLM and a number of commercial providers distribute NDC code lists. OHDSI is trying to create a list as complete as possible by combining many sources and adding NDC codes found in observational databases. If NDC codes are missing from the CONCEPT table, please report those to the OHDSI forum.

NDCs are also reported in different format variants. OHDSI adopts the standardized format used by the NLM and described in Section 6 of the RxNorm documentation.