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Clarify the Complexity Please! NDC Codes and Drug Classification Systems

Christine Woolstenhulme, QMC QCC CMCS CPC CMRS

Different Drug classification systems are used to categorize drugs to identify the medication, with each system having their own logic. There are four main drug classification systems used in the United States, not to be confused with a class of drugs or "Drug Class". A drug class is the way drugs are grouped or classified according to the therapeutic use, reactions, and chemical structure. This article will address the main drug classification systems and the different ways drugs are identified for billing, research, and reporting.  

National Drug Code (NDC)

NDC- Divides into package size or manufacturer, displayed on the packaging in a 10-digit format. However, when billing with an NDC #, it is required to report 11-digits using a 5-4-2 format.

Converting NDC's from 10-digits to 11-digits 

When a drug is only showing 10 digits a -0- should be used to report the correct number of codes required. The -0- is placed in the position that is missing the correct number in the segment. 

NDC numbers are broke down into 3 code segments (XXXXX – XXXX – XX)

  • The first series XXXXX- Labeler code (manufacturer)
  • The second series XXXX - Product code (strength, dosage form, formulation)
  • The third series XX - Package code (package size/type)

NDC's may be shown in different formats, and be the same code like the example below shows 


The correct way to report this using the 5-4-2 format is 68982-0348-01

          5       4    2
      68982     0348    01

There are several types of drug classification systems. We will cover the following in this article:

  • Generic Product Identifier (GPI)
  • American Hospital Formulary System (AHFS)
  • Generic Code Number (GCN)
  • Consolidated Mail Outpatient Pharmacy (CMOP)

In addition, there are multiple ways to lookup drug products with different identifiers, such as NDC, GPI, GSN, GCN, RXNorm and VA CMOP ID.

Generic Product Identifier (GPI) - Used to collect and analyze how a drug class performs, review population usage and understanding costs. 

GPIs use several tier levels to identify drug products by using a hierarchical therapeutic classification tier system. It does not take into consideration package size or manufacturer. 

Products having the same 14-character GPI are identical with respect to the active ingredient(s), dosage form, route, and strength or concentration. The GPI does not consider the presence of inactive ingredients.  

For more information, refer to the following article: GPI Codes - Generic Product Identifiers.

The first 2 Digits = MAJOR CLASS  Vaccine 17  VACCINES
The first 4 Digits = MAJOR SUBCLASS Viral  17-10  Viral Vaccines
The first 6 Digits = MINOR SUBCLASS Influenza 17-10-00  Viral Vaccines
The first 10 Digits = MEDICATION NAME  Split Quadrivalent 17-10-00-20-25 Influenza Virus Vaccine Split Quadrivalent
The first 12 digits = MEDICATION NAME AND DOSAGE FORM Suspension 17-10-00-20-25-18  Influenza Virus Vaccine Split Quadrivalent Suspension

GPI # 17-10-00-20-25-18-00  Influenza Virus Vaccine Split Quadrivalent IM Inj.

     17  Vaccines/Toxoids/Passive Immunizing/Allergenic Extracts/Misc
     17  *VACCINES*
     17-10  *Viral Vaccines**
     17-10-00  *Viral Vaccines***
     17-10-00-20  Influenza Virus Vaccine
     17-10-00-20-25  Influenza Virus Vaccine Split Quadrivalent
     17-10-00-20-25-18  Influenza Virus Vaccine Split Quadrivalent Suspension
     17-10-00-20-25-18-00  Influenza Virus Vaccine Split Quadrivalent IM Inj

Therefore, you know if you see 17 as the first couplet it is a vaccine, if it is 17-10 it is a viral vaccine, etc.

  • 17 = VACCINE
  • 18 = TOXOIDS

American Hospital Formulary System (AHFS) - The AHFS also has a classification system used in the  Pharmacologic/Therapeutic Classification (PC), which is used by the International Pharmaceutical Abstracts (IPA) for clinical studies.

Generic Code Number (GCN) - A GCN is a standard number assigned by a drug pricing service called First DataBank. The GCN identifies each strength, formulation, and route of administration of a drug entity. Each drug has its own unique GCN. One drug entity may have multiple GCNs, depending on the product's available strengths (e.g., 50 mg, 100 mg, etc.), forms (e.g., tablet, capsule, liquid, etc.), and routes of administration (e.g., oral, transdermal, injectable, etc.).

Consolidated Mail Outpatient Pharmacy (CMOP) - The VA uses a National Drug file (NDF) and processes medications for veterans through the Consolidated Mail Outpatient Pharmacy (CMOP).