pharmaceutical code pharmaceutical code pharmaceutical codes are used in medical classification to uniquely identify medication. they may uniquely identify an active ingredient, drug system (including inactive ingredients and time-release agents) in general, or a specific pharmaceutical product from a specific manufacturer. examples drug system identifiers (manufacturer-specific including inactive ingredients): national drug code (ndc) — administered by food and drug administration. drug identification number (din) — administered by health canada under the food and drugs act hong kong drug registration — administered by the pharmaceutical service of the department of health (hong kong) national pharmaceutical product index - south africa hierarchical systems: anatomical therapeutic chemical classification system (at, or atc/ddd) — administered by world health organization generic product identifier (gpi) — hierarchical classification number published by medispan snomed — c axis ingredients: unique ingredient identifier proprietary database identifiers include those assigned by first databank, micromedex, medispan, gold standard drug database (published by elsevier), and cerner multum medisource lexicon; these are cross-indexed by rxnorm, which also assigns a unique identifier (rxcui) to every combination of active ingredient and dose level.