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:

While most sources of drug/class relationships relate ingredients to classes, some sources relate products to classes. To facilitate comparison of classes from distinct sources, RxClass ordinarily displays a normalized view of class members as ingredients, transparently translating products to their ingredients. Alternatively, you can view class members as provided by the source, including any ID or name in the mapped vocabulary, by selecting the Show Source Data checkbox.

When the show source data 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, CSA Schedule, VA and ATC Product map drug products to these classes. When the source data box is checked, 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.

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 groups drugs 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.
• 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 ten sources which associate generic drugs to the classes listed above.

• ATC. Drug (ingredient-level) ATC class members are curated by the World Health Organization Collaborating Center for Drug Statistics Methodology.
• ATCPROD. Drug (product-level) ATC class members are curated by the National Library of Medicine.
• 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.
• 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: 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.

The following table lists the class-member sources available in RxClass for each type of class.

Multiple sources map drugs to some class types. RxClass presents them as alternatives. For example, RxClass shows Chem class members from DailyMed by default, but you may select FDASPL or MEDRT instead, by choosing Edit Drug Sources.

The table below marks with “X” the sources of drug/class mappings, and marks with “X**” the source shown in RxClass by default.

Class Type	Drug Source
	ATC	ATCPROD	DailyMed	FDASPL	FMTSME	MEDRT	RXNORM	SNOMEDCT	VA
ATC1-4	X	X**
Chem			X**	X		X
Disease						X
DISPOS								X
EPC			X**	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 term types of RxNorm drug concepts that are members of a class (identified by class type and membership source) and the relationship by which RxClass signals the association.

Drug Source	Class Type	Relation	Member Types	Description
ATC	ATC1-4		IN MIN PIN	Drug (ingredient-level) ATC class membership curated by the World Health Organization Collaborating Center for Drug Statistics Methodology
ATCPROD	ATC1-4		BPCK GPCK SBD SCD	Drug (product-level) ATC class membership curated by the National Library of Medicine
DailyMed	EPC	has_EPC	IN MIN PIN	Drug members of a FDA Established Pharmacologic Class
DailyMed	Chem	has_Chemical_Structure	IN MIN PIN	Drugs that have a chemical structure
DailyMed	MoA	has_MoA	IN MIN PIN	Drugs that have a Mechanism of Action
DailyMed	PE	has_PE	IN MIN PIN	Drugs that have a Physiologic Effect
FDASPL	EPC	has_EPC	IN MIN PIN	Drug members of a FDA Established Pharmacologic Class
FDASPL	Chem	has_Chemical_Structure	IN MIN PIN	Drugs that have a chemical structure
FDASPL	MoA	has_MoA	IN MIN PIN	Drugs that have a Mechanism of Action
FDASPL	PE	has_PE	IN MIN PIN	Drugs that have a Physiologic Effect
FMTSME	TC	has_TC	IN MIN PIN	Drugs that have Therapeutic Categories
MEDRT	Chem	CI_ChemClass	IN MIN PIN	Drugs that are contraindicated with a chemical class
MEDRT	Chem	has_ingredient	IN MIN PIN	Drugs that are members of a chemical class
MEDRT	Chem	has_active_metabolites	IN MIN PIN	Drugs that have active metabolites in a chemical class
MEDRT	Disease	CI_with	IN MIN PIN	Drugs that are contraindicated with a disease
MEDRT	Disease	induces	IN MIN PIN	Drugs that induce a disease
MEDRT	Disease	may_diagnose	IN MIN PIN	Drugs that may diagnose a disease
MEDRT	Disease	may_prevent	IN MIN PIN	Drugs that may prevent a disease
MEDRT	Disease	may_treat	IN MIN PIN	Drugs that may treat a disease
MEDRT	MoA	CI_MoA	IN MIN PIN	Drugs that are contraindicated with a Mechanism of Action
MEDRT	MoA	has_MoA	IN MIN PIN	Drugs that have a Mechanism of Action
MEDRT	PE	CI_PE	IN MIN PIN	Drugs that are contraindicated with a Physologic Effect
MEDRT	PE	has_PE	IN MIN PIN	Drugs that have a Physiologic Effect
MEDRT	PK	has_PK	IN MIN PIN	Drugs that are members of a Pharmacokinetics Class
MEDRT	PK	site_of_metabolism	IN MIN PIN	Drugs that have a site of metabolism in a Pharmacokinetics Class
RXNORM	Schedule	has_schedule	primarily BPCK GPCK SBD SCD; few IN PIN	Drugs that are considered controlled substances under the Controlled Substances Act (CSA)
SNOMEDCT	DISPOS	isa_disposition	IN MIN PIN	Drugs that have a "disposition" (e.g., mechanism of action)
SNOMEDCT	STRUCT	isa_structure	IN MIN PIN	Drugs that have a chemical structure
SNOMEDCT	THERAP	isa_therapeutic	IN MIN PIN	Drugs that have a therapeutic role
VA	VA	has_VAClass	primarily BPCK GPCK SBD SCD SCDF SCDG; few IN MIN PIN	Clinical drugs that are members of a VA Class
VA	VA	has_VAClass_extended	GPCK SBD SCD	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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