RxClass - Frequently Asked Questions


Class Browser

What do the numbers signify after the class names in the Class Browser?
The numbers indicate how many RxNorm generic drugs are associated with the class.


Can the search for a drug class use an identifier instead of a name?
Yes, RxClass allows search by MED-RT identifier (NUI) for the EPC, MoA, PE, and PK drug classes. For ATC classes, an ATC identifier (ex:N01AB) is allowed. For MeSH pharmalogical actions, CHEM and disease drug classes, a MeSH identifer (ex:D058633) is accepted. The RxClass autocomplete feature will identify the class name when the identifier is entered.
Can I search drug classes with synonyms?
Yes, RxClass has incorporated many synonyms to aid in searching for drug classes. For example, entering "Lou Gehrig's Disease" will find the Disease class "Amyotrophic Lateral Sclerosis".
Can a RxCUI be used in the search?
The RxNorm identifier (RxCUI) can be used when searching for a drug name (when the "by RxNorm drug name/id" button is selected under the search area), but not for a drug class.
Can an NDC code be used in the search?
No, the only drug name identifiers allowed in the search are RxNorm identifiers (RxCUIs).
Can the drug name search handle brand names such as Tylenol?
Yes, brand names can be used in the drug name search.

Sources of Drug-Class Relations

What is the difference between DailyMed and FDASPL drug members?
While both DailyMed and FDASPL map to the same class trees, they associate with the drugs in two different ways. DailyMed associates the drug classes with drugs defined by a unique ingredient identifier (UNII) code. FDASPL associations are maintained as part of the MED-RT vocabulary, and the drug classes are associated by relations (called roles in MED-RT) through the drugs defined by RxNorm identifiers. See the overview for more information on the drug sources and the classes they associate with.
Why can't I check both DailyMed and FDASPL?
DailyMed and FDASPL associate drug members to the same class trees, and often contain the same drug members. We have chosen to allow users to only select one drug source for each class type to eliminate confusion by not displaying possible overlapping and redundant information.

Drug Member Display

Can the table be sorted on any column in the display?
Yes, sorting the table based on a single column can be done by single clicking the column header.
What does "INDIRECT" or "DIRECT" mean in the Relation column in the display?
A DIRECT relation means that the drug member is directly associated to the drug class. An INDIRECT relation means that the drug member is associated to a subclass of the selected class.
Can the table be bookmarked?
Yes. There is an icon with the arrow pointing down, just right of the class name under the search box on the class details page. Click that icon to bookmark that page until the end of your browsing session.