A sample view of the RxClass Browser is shown below.

RxClass allows users to search by class name or identifier to find the RxNorm drug members or, conversely, search by RxNorm drug name or identifier to find the classes that the RxNorm drug is a member of.

The RxClass search bar is shown below.

The search by class can be done either by navigating the class tree in the left side of the RxClass window, or by typing in a name in the search box. When typing in a class name, RxClass will give suggestions of class names containing the string. For example, when the term “coxib” is entered in the search box, the following class suggestions are provided:

A search by drug name or RxCUI will bring up a pop-up menu containing all the classes the drug is a member of. The example below shows the window when the name “fomivirsen” is entered as a drug name:

When the show data source box is checked, additional columns will be displayed in the drug table showing the source data that is mapped into RxNorm. The following images show the tables without and with the source data.

By default, RxClass does not show source data and the drug table(s) are displayed as ingredients. While most drug to class mappings occur at the ingredient level, two class types – CSA Schedule and VA classes – map drug products to these classes. When the data source box is enabled for those classes the drug products are shown in the table. For example:

Additionally, once a class is selected, RxClass offers similar classes in drug membership.

Note: In June 2018, NDF-RT was replaced by MED-RT as a source of drug class relations. Additionally, the VA drug-class relations contained in NDF-RT were replaced by VANDF data.

SNOMED CT® Usage Conditions RxClass includes SNOMED Clinical Terms® (SNOMED CT®) which is used by permission of the International Health Terminology Standards Development Organisation (IHTSDO). All rights reserved. SNOMED CT® was originally created by the College of American Pathologists. “SNOMED”, “SNOMED CT” and “SNOMED Clinical Terms” are registered trademarks of the IHTSDO. Use of SNOMED CT in RxClass is subject to the SNOMED CT Affiliate license provisions (incorporated in the License Agreement for Use of the UMLS Metathesaurus as Appendix 2) issued by the National Library of Medicine on behalf of SNOMED International.

Class Types

RxClass contains fourteen drug class trees displayed on the left side of the view.



The class types are explained below:

• ATC1-4 - Anatomical Therapeutic Chemical (ATC) containing class levels 1 through 4. The ATC classification system divides the drugs into different groups according to the organ or system on which they act and according to their chemical, pharmacological and therapeutic properties. The drugs are divided into 14 main groups (first level), with two therapeutic/pharmacological subgroups (second and third levels). The fourth level is a therapeutic/pharmacological/chemical subgroup and the fifth level is the chemical substance. The second, third and fourth levels are often used to identify pharmacological subgroups when these are considered to be more appropriate than therapeutic or chemical subgroups.
• Chem - Chemical structure and classification containing chemicals or other drug ingredients, organized into a chemical structure classification hierarchy. The high level non-MeSH classes, including the top level node of "Substances and Cells", were created as parents of the MeSH classes contained in the tree, which are part of the drugs and chemicals ("D" tree) category in MeSH. Note that some relations from MED-RT may not be included if they map to classes not contained in the Chem tree.
• Disease - Disease classification containing pathophysiologic as well as certain non-disease physiologic states that are treated, prevented, or diagnosed by an ingredient or drug product. May also be used to describe contraindications. The high level non-MeSH classes, including the top level node of "Diseases, Life Phases, Behavior Mechanisms and Physiologic States”, were created as parents of the MeSH classes contained in the tree. Specifically, the RxClass Disease tree incorporates the following high-level MeSH classes (MeSH tree ids in parenthesis) and their subclasses:
  • Diseases (C)
  • Behavior and Behavior Mechanisms (F01)
  • Mental Disorders (F03)
  • Reproductive Physiological Phenomena (G08.686)
  • Immune System Phenomena (G12)
  • Age Groups (M01.060)
  Note that some MED-RT disease relations may not be included if they map to classes not contained in the tree.
• DISPOS - Drug classification from SNOMED CT based on the “dispositions” of medicinal products (e.g., mechanism of action).
• EPC - FDA Established Pharmacologic Classes. In support of the FDA Structured Product Labeling (SPL) initiative, a hierarchy of FDA. Established Pharmacologic Class (EPC) concepts are contained in MED-RT.
• MeSHPA - Medical Subject Headings (MeSH) pharmacological actions. In MeSH, every drug and chemical MeSH heading has been assigned one or more headings that describe its pharmacological action (PA).
• MoA - Mechanism of Action in MED-RT, containing molecular, subcellular, or cellular effects of drug generic ingredients, organized into a chemical function classification hierarchy, beneath the “Cellular or Molecular Interactions” concept.
• PE - Physiologic Effects in MED-RT, containing tissue, organ, or organ system effects of drug generic ingredients, organized into an organ system classification hierarchy, beneath the “Physiological Effects” concept.
• PK - Pharmacokinetics in MED-RT, containing collections of concepts describing the absorption, distribution, and elimination of drug active ingredients, beneath the “Clinical Kinetics” concept.
• Schedule - The Controlled Substances Act (CSA) drug schedules(1-5), whose members are drug products (generic and branded).
• STRUCT - Drug classification from SNOMED CT based on the chemical structure of medicinal products.
• TC - Therapeutic Categories from MED-RT, a small, experimental collection of general therapeutic intents of drug generic ingredients, organized into an organ system-oriented classification hierarchy, beneath the “Therapeutic Categories [TC]” concept.
• THERAP - Drug classification from SNOMED CT based on the therapeutic role of medicinal products and medicinal product forms.
• VA - VA drug classes from VANDF, whose members are clinical drugs.

Sources of Drug-Class Relations

There are nine sources which associate generic drugs to the classes listed above.

• ATC (level 5). The fifth level of the ATC tree contains the drugs.
• DailyMed. The DailyMed API maps substances through their UNII Code values to EPC, Chem, MoA and PE classes.
• FDASPL. The FDASPL drug source maps drug concepts in MED-RT to EPC, Chem, MoA and PE classes.
• FMTSME. The FMTSME drug source maps drug concepts in MED-RT to TC classes.
• MEDRT. Drug concepts in MED-RT are associated to Disease, MoA, Chem, PE, and PK classes.
• MeSH. MeSH drugs are associated with the pharmacological actions.
• RxNorm. CSA schedules for drug products are contained in the RxNorm data set in several drug sources.
• SNOMEDCT. Drug classes (groupers) from the medicinal product hierarchy of the U.S. Edition of SNOMED CT, linked to medicinal products and medicinal product forms (as RxNorm ingredients).
• VA. The VA drugs are associated with the VA classes.

Note: the three sources - DailyMed, MEDRT and FDASPL - contain overlapping and redundant associations of drugs to some of the class trees (see tables below), so to avoid confusion only one of those sources is selected at any given time in RxClass.

The following table lists the drug sources and the classes they associate with .

Class Type \ Source	ATC	DailyMed	FDASPL	FMTSME	MEDRT	MeSH	RXNORM	SNOMEDCT	VA
ATC1-4	X
Chem		X	X		X
Disease					X
DISPOS								X
EPC		X	X
MeSHPA						X
MoA		X	X		X
PE		X	X		X
PK					X
Schedule							X
STRUCT								X
TC				X
THERAP								X
VA									X

Relationships to Drug Classes

The following table shows the relationships each drug source uses to identify with the drug class.

Drug Source	Relation	Class Type	Description
ATC (level 5)		ATC1-4	Drug members of an ATC class
DailyMed	has_EPC	EPC	Drug members of a FDA Established Pharmacologic Class
DailyMed	has_Chemical_Structure	Chem	Drugs that have a chemical structure
DailyMed	has_MoA	MoA	Drugs that have a Mechanism of Action
DailyMed	has_PE	PE	Drugs that have a Physiologic Effect
FDASPL	has_EPC	EPC	Drug members of a FDA Established Pharmacologic Class
FDASPL	has_Chemical_Structure	Chem	Drugs that have a chemical structure
FDASPL	has_MoA	MoA	Drugs that have a Mechanism of Action
FDASPL	has_PE	PE	Drugs that have a Physiologic Effect
FMTSME	has_TC	TC	Drugs that have Therapeutic Categories
MEDRT	CI_ChemClass	Chem	Drugs that are contraindicated with a chemical class
MEDRT	has_ingredient	Chem	Drugs that are members of a chemical class
MEDRT	has_active_metabolites	Chem	Drugs that have active metabolites in a chemical class
MEDRT	CI_with	Disease	Drugs that are contraindicated with a disease
MEDRT	induces	Disease	Drugs that induce a disease
MEDRT	may_diagnose	Disease	Drugs that may diagnose a disease
MEDRT	may_prevent	Disease	Drugs that may prevent a disease
MEDRT	may_treat	Disease	Drugs that may treat a disease
MEDRT	CI_MoA	MoA	Drugs that are contraindicated with a Mechanism of Action
MEDRT	has_MoA	MoA	Drugs that have a Mechanism of Action
MEDRT	CI_PE	PE	Drugs that are contraindicated with a Physologic Effect
MEDRT	has_PE	PE	Drugs that have a Physiologic Effect
MEDRT	has_PK	PK	Drugs that are members of a Pharmacokinetics Class
MEDRT	site_of_metabolism	PK	Drugs that have a site of metabolism in a Pharmacokinetics Class
MeSH		MeshPA	Drug members of a MeSH Pharmacologic Action
RXNORM	has_schedule	Schedule	Drugs that are considered controlled substances under the Controlled Substances Act (CSA)
SNOMEDCT	isa_disposition	DISPOS	Drugs that have a "disposition" (e.g., mechanism of action)
SNOMEDCT	isa_structure	STRUCT	Drugs that have a chemical structure
SNOMEDCT	isa_therapeutic	THERAP	Drugs that have a therapeutic role
VA	has_VAClass	VA	Clinical drugs that are members of a VA Class
VA	has_VAClass_extended	VA	Related clinical and branded drugs that are derived members of a VA Class. For example, branded drugs related to clinical drugs that are mapped to a VA class, or clinical drugs that have a different dosages from ones that are mapped to a VA class.

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