The Category field in the portal contains data taken from the MeSH Pharmacological Action (PA) vocabulary. It has cross references from the MeSH file, as well as some added by NLM. You may search these using the “By Category” radio button.
Once you retrieve a drug record, you may search for the Categories that may be listed in the box below the name by clicking on them. These will retrieve other drug records that are also categorized in this way.
General drug classes can be also searched by using the generic name stem of a drug. A table of these stems are available. They may be searched in the name search box by using asterisks for truncation, such as *azepam* to find drug names that correspond to antianxiety drugs such as Lorazepam.