NDC (National Drug Codes) is a coding system used for drugs commercially available in the US. NDC consist of three components:
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.
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.
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.
NDC are not used as Standard Concepts.
NDC concepts are either listed as full 11-digit or as shorted 9-digit (omitting the 2-digit packaging information) codes. The Concept Classes are “11-digit NDC” and “9-digit NDC” respectively.
Most NDC are listed under the Drug Domain. However, those that can be asigned to Medical Devices have the Device Domain, and cosmetics, supplements, medical foods and allergens are assigned Observation Domain.
NDCs are mapped to RxNorm
There is a problem that NDC can update the vocabulary using the same concepts for a different drug concepts: in the 18/12/17 release we found out that:
44865343 “Aminophylline 200 MG Oral Tablet” changed to “Cephalexin 500 MG Oral Capsule”
45092451 “Aluminum Hydroxide 200 MG / Magnesium Hydroxide 200 MG Oral Tablet [Rulox #1]” changed to “Allopurinol 100 MG Oral Tablet”
45084807 “GLIMEPIRIDE 4 MG TABLET” changed to “Naproxen sodium 550 MG Oral Tablet” (number provided is the concept_id)
so these concepts totally changed their meaning during the update