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 numbers)
3. packaging information (up to 2 numbers)

The FDA assigns the manufacturer number to each manufacturer. Manufacturer can be an organization which actually manufactures the drug, or a reseller or distributor. The manufacturer is responsible for the product code and packaging information. This system is not 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 for different products.

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 from observational databases. If NDC codes are missing from the CONCEPT table, please report those cases to the OHDSI forum.

NDCs are also mentioned in different formats. OHDSI adopts the standardized form used by the NLM and described in Section 6 of the RxNorm documentation.