What is the code used to identify drugs? A Guide to NDC, ATC, and More

The U.S. Food and Drug Administration (FDA) maintains a directory of all listed drugs, each identified by a unique code [1.2.2]. So, what is the code used to identify drugs? It's a system of unique identifiers crucial for safety and tracking, with the National Drug Code (NDC) being the US standard [1.2.1].

Quick Summary

The primary system for drug identification in the U.S. is the National Drug Code (NDC) [1.2.1]. Other global systems like the ATC and terminologies like RxNorm also play vital roles in classification and interoperability [1.4.1, 1.5.2].

Key Points

• Primary US Identifier: The National Drug Code (NDC) is the main code used in the United States to identify drugs for distribution and billing [1.2.1].

• NDC Structure: An NDC is a unique 10 or 11-digit, 3-segment number identifying the labeler, product, and package size [1.2.3].

• Global Classification: The Anatomical Therapeutic Chemical (ATC) system is a global standard from the WHO that classifies drugs by their therapeutic use [1.4.1].

• Clinical Interoperability: RxNorm is a terminology that normalizes drug names and codes, enabling different health IT systems to communicate effectively [1.5.2].

• Safety and Tracking: These codes are essential for preventing medication errors, managing the supply chain, and monitoring drug safety (pharmacovigilance) [1.8.1, 1.8.4].

• International Systems: Canada uses an 8-digit Drug Identification Number (DIN) for its regulatory system [1.6.1].

• Billing Format: For billing purposes in the U.S., NDCs are often converted to a standardized 11-digit format (5-4-2) [1.2.4].

The Core of Drug Identification

In the complex world of pharmaceuticals, accurately identifying a specific medication is critical for patient safety, supply chain management, and proper billing [1.8.1, 1.8.4]. The answer to the question, "What is the code used to identify drugs?" is not a single code but a collection of systems working in concert. In the United States, the primary identifier is the National Drug Code (NDC), a standard overseen by the Food and Drug Administration (FDA) [1.2.1]. However, other international and clinical systems, such as the Anatomical Therapeutic Chemical (ATC) classification and RxNorm, are also essential.

The National Drug Code (NDC): The US Standard

The NDC is a unique, universal product identifier for human drugs in the United States [1.2.4]. Every prescription and over-the-counter medication package is required to have this code, which provides transparency throughout the healthcare supply chain [1.3.1, 1.8.3].

Structure of the NDC

Each NDC is a 10 or 11-digit number composed of three distinct segments [1.2.3, 1.3.2]:

• Labeler Code: This first segment consists of 4, 5, or 6 digits and is assigned by the FDA [1.2.3, 1.2.6]. It identifies the specific firm that manufactures, repacks, or distributes the drug product [1.3.3].
• Product Code: The second segment, with 3 or 4 digits, is assigned by the labeler [1.3.3]. It identifies the drug's specific strength, dosage form (e.g., tablet, capsule), and formulation [1.2.1].
• Package Code: The final segment, with 1 or 2 digits, is also assigned by the labeler [1.3.3]. It specifies the package size and type [1.2.1].

These segments can appear in different configurations, such as 4-4-2, 5-3-2, or 5-4-1 [1.2.3]. For billing purposes, especially for claims submitted to the Centers for Medicare & Medicaid Services (CMS), the 10-digit NDC is often converted to a standardized 11-digit format by adding a leading zero to one of the segments to create a 5-4-2 structure [1.2.4, 1.3.1].

The Anatomical Therapeutic Chemical (ATC) System: A Global Perspective

While the NDC is U.S.-centric, the Anatomical Therapeutic Chemical (ATC) Classification System provides a global standard for drug research and monitoring [1.4.5]. Maintained by the World Health Organization (WHO), the ATC system classifies the active ingredients of drugs, not the commercial product itself [1.4.1].

Structure of the ATC Code

The ATC system has a five-level hierarchical structure [1.4.4]:

1. Level 1: A single letter for the main anatomical group (e.g., 'N' for Nervous System).
2. Level 2: Two digits for the therapeutic main group.
3. Level 3: A letter for the pharmacological/therapeutic subgroup.
4. Level 4: A letter for the chemical/pharmacological/therapeutic subgroup.
5. Level 5: Two digits for the chemical substance.

For example, one of aspirin's codes is N02BA01, which breaks down its classification from the nervous system down to the specific chemical substance [1.4.1]. This system is vital for drug utilization research, allowing health organizations worldwide to compare and analyze drug consumption statistics [1.4.5].

Other Key Drug Identification Systems

Beyond the NDC and ATC, several other systems play crucial roles.

RxNorm: The Language of Interoperability

RxNorm, produced by the U.S. National Library of Medicine, serves as a normalized naming system that helps different health IT systems communicate effectively [1.5.2]. It links various drug vocabularies and codes. For instance, different NDCs from various manufacturers for the same drug (e.g., naproxen 250mg oral tablet) can be grouped under a single RxNorm Concept Unique Identifier (RxCUI) [1.5.5]. This is essential for preventing ambiguity in electronic health records (EHRs) and e-prescribing [1.5.4].

International and Commercial Codes

• Drug Identification Number (DIN): In Canada, drugs are identified by an 8-digit DIN assigned by Health Canada. It confirms that the drug has been evaluated and authorized for sale in Canada [1.6.1, 1.6.4].
• Global Trade Item Number (GTIN): This is a global standard used to identify trade items in the supply chain, often seen as a barcode on packaging [1.7.4]. For pharmaceuticals, the GTIN can be used to encode the NDC along with a unique serial number, creating a Serialized National Drug Code (sNDC) for enhanced tracking and tracing [1.2.5].

Comparison of Major Drug Coding Systems

Feature	National Drug Code (NDC)	Anatomical Therapeutic Chemical (ATC)	RxNorm
Governing Body	U.S. Food and Drug Administration (FDA) [1.2.1]	World Health Organization (WHO) [1.4.1]	U.S. National Library of Medicine (NLM) [1.5.5]
Primary Purpose	Identification for U.S. distribution & billing [1.2.1]	Therapeutic & pharmacological classification for research [1.4.5]	Semantic interoperability in EHRs [1.5.2, 1.5.4]
Geographic Scope	Primarily United States [1.2.1]	International [1.4.1]	Primarily United States [1.5.5]
Code Structure	3-segment numeric (Labeler-Product-Package) [1.2.1]	5-level alphanumeric hierarchy [1.4.4]	Concept Unique Identifiers (RxCUI) [1.5.5]
What it Identifies	Specific drug product & package size [1.2.3]	Active ingredient's therapeutic use [1.4.1]	Normalized clinical drug concepts [1.5.5]

Conclusion

There is no single answer to "what is the code used to identify drugs?" because the context dictates the system used. The NDC is the foundational code for identifying and tracking specific drug products and packages within the U.S. healthcare system, crucial for everything from pharmacy dispensing to insurance reimbursement [1.8.4]. The ATC system provides a global framework for classifying drugs by their function, enabling international research and statistics [1.4.5]. Meanwhile, terminologies like RxNorm are the digital glue, ensuring that data about these drugs can be exchanged and understood accurately across different software and systems [1.5.2]. Together, this multi-layered approach to drug coding forms the backbone of modern medication management, ensuring safety and efficiency from the manufacturer to the patient.

For more information, you can visit the FDA's National Drug Code Directory.

Frequently Asked Questions

Is the NDC number the same as a prescription number?

No. The NDC is a universal product identifier for the drug itself, found on the manufacturer's package [1.2.4]. A prescription number is assigned by a pharmacy to identify a specific patient's order.

Can I look up a drug by its NDC number?

Yes, you can look up a drug by its NDC using online databases such as the FDA's National Drug Code Directory or the National Library of Medicine's DailyMed website [1.2.2, 1.9.2].

Is an NDC required on all drug packaging?

The NDC is present on all prescription and over-the-counter medication packages and inserts in the United States [1.3.1]. However, not all listed drugs are in the NDC directory, such as animal drugs or blood products [1.2.4].

What is the main difference between an NDC and an ATC code?

The NDC identifies a specific drug product and its package size for commercial distribution and billing in the U.S. [1.2.1]. The ATC code classifies a drug's active substance based on its therapeutic and pharmacological properties for research purposes globally [1.4.1].

Who assigns the NDC number?

The first segment of the NDC, the labeler code, is assigned by the FDA. The other two segments, the product and package codes, are assigned by the drug manufacturer or distributor [1.2.3].

Does having an NDC number mean the FDA has approved the drug?

Not necessarily. The presence of an NDC number on a drug label does not denote FDA approval. The NDC Directory contains unapproved drugs as well as approved ones [1.2.2].

How is RxNorm different from an NDC?

An NDC identifies a specific package from a specific manufacturer [1.2.1]. RxNorm is a higher-level naming system that groups all NDCs for the same clinical drug (e.g., same ingredient and strength) under a single concept, which aids in data interoperability [1.5.5].