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Health Informatics Standards and Big Data Challenges – Part I: Controlled Vocabularies for Drugs

The importance of a hermetic integration and interoperability between different systems in healthcare informatics research and management networks have been revealed before in previous blogs.

Different standards were developed through different organizations trying to reach an optimum solution to control vocabularies for a smooth and accurate data transfer between different systems.

Some of the most important controlled vocabularies have been introduced in brief in a previous blog.

This blog will concentrate on the vocabularies related to drugs with a focus on the RxNorm standard.

Many trials were made to put a basis for a controlled drug vocabulary.  The most prominent were:

Anatomical-Therapeutic-Chemical criteria (ATC)

ATC is a drug dictionary that could be considered as a subset of the WHO (World Health Organization) drug dictionary.

Every year 2000 new drugs are added to the ATC dictionary.  Different inputs come from 34 countries.

National Drug Codes (NDC)

The National Drug Codes (NDC) is a drug classification designed by the FDA.

NDC is an 11-digit code system that is divided into three parts. It is based on the drug manufacturer, and each manufacturer defines the specific codes for their products.

The NDC coding system has serious weakness points.  It is not designed in the form of a uniform hierarchy, so the codes may be redundant.

Another weak point is that similar drugs are not grouped.

These weakness points created a motive for the development of a new controlled vocabulary standard, namely RX-Norm.


RxNorm is developed by the National Library of Medicine and affords standardized names for clinical drugs. It covers only US drugs.  The names are linked to vocabularies that are frequently used in drug-interaction software and pharmacy-management applications.  The vocabularies used are those of Multum (the leaflets that provide the basic consumer drug information like drug descriptions, interactions, the side effects and the instructions for use), the First Databank, Micromedex, and the Gold Standard Drug Database.  It can be considered the main standard for any ePrescription system.

Through affording linkage between these vocabularies, RxNorm can guarantee smooth data transfer and transaction between different systems.

RxNorm now includes the United States Pharmacopeia (USP) Compendial (nonproprietary) Nomenclature.

USP is a cumulative data set of all Active Pharmaceutical Ingredients (API).

It includes information about the active ingredient, the strength and the dose of the drug.

RxNorm Files

They have the following properties:

  • They are pipe-delimited text files
  • Available in Rich Release Format (RRF)
  • They do not require the use of the MetamorphoSys program provided with the UMLS Knowledge Sources Files
  • The character set of RxNorm release files is Unicode UTF-8

If you care about obtaining clean and well-reviewed data in standardized formats, John Snow Labs catalog can be an ideal repository for you.  It contains a full RxNorm Drug Terminologies Data Package.  This data package includes many valuable datasets related to drug terminologies.  It includes datasets for RxNorm Prescription Drugs Names And Identifiers, RxNorm Attributes Data For Concepts And Atoms, RxNorm Archived Atoms InformationRxNorm Prescription Drugs Relationships Between Concepts And Atoms, and many more.

RxNorm Browser

RxNav 2.0 (the current version) is a browser for several drug information sources developed by the National Library of Medicine (NLM).  It handles different data sets like RxNorm, RxTerms, DrugBank databases, RxIMAGE API (for pill information), and DailyMed API (for NDC packaging).  Besides, it finds drugs in RxNorm from the names and codes.

RxNorm API

Currently, there are 2 types of APIs:

1. RxNorm RESTful Web API

It is a web service developed at the National Library of Medicine for accessing the RxNorm data.

Representational state transfer (REST) is a client/server architecture used for distributed hypermedia systems such as the World Wide Web.

The Client submits a request to the server where it is processed, and a response is sent back to the client.

2. RxNorm SOAP API

will be terminated on January 2020.

National Council for Prescription Drug Programs (NCPDP)

NCPDP is the standard used for a smooth transfer of prescription information and for billing retail drug sales.

For any software to be qualified as an e-prescribing program, it must use the most updated and accredited NCPDP Script standard.

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