Appended below is a posting from the PCORI DSSNI group that provides a link to a presentation on the RxNorm suite given by Olivier Bodenreider. Folks can listen to the presentation if they wish. However, I posted the entire email because of one of the comments in the Chat Log that Shelly included in her email. I bolded the comment from Olivier that caught my eye about not using the legacy VA drug hierarchy but the recommendation to use classes from DailyMed or ATC instead.
Interested in hearing reactions from those on this list who have used the existing drug classes.
Michael Kahn
Good morning,
Dr. Bodenreider’s presentation has the honor of being the largest audience in the history of PCORnet Office Hours! We’re very grateful to him for sharing his expertise with us, and looking forward to further discussion and work.
The recording of this session is posted here: https://pcornet.centraldesktop.com/pcornetmain/folder/3659277/#folder:4504165
With thanks to Becky Wilgus, here are the questions that came in at the close of our session today with Dr. Bodenreider’s responses:
From Jessica Tenenbaum :
Is it possible to take advantage of this new class functionality to enable hierarchical searching of RxNorm coded drugs in i2b2? Know of any groups doing that?
Olivier Bodenreider:
I believe it is, Jesse. The classes (regardless of source) are linked directly to RxCUIs. The API provides not only the drug-class relations, but also the hierarchy of the classes, so class-enabled search should be possible (as it is in RxClass)
from Roy Pardee (GHRI) to Everyone:
@Jessica–it’s not so slick, but we imported the VA’s class hierarchy out of UMLS to create a hierarchy for our i2b2.
Olivier Bodenreider:
I had heard about i2b2 using the VA classes from a question sent to us (about why there were not available through RxClass).
I would recommend against using the “legacy” VS classes, because they are no longer used in any clinical system. The classes from DailyMed or ATCseem more reliable and appropriate.
The small advantage the VA classes offer (at least in theory) is the ability to take into account the route of
administration in the class assignment – SCDs, not INs, are linked to VA classes.
from Rahul Jain to Everyone:
interesting i2b2 discussion… would be interested in learning more.
Olivier Bodenreider:
Keep your questions coming 
Send them to RXNAVINFO@LIST.NIH.GOV. We are happy to help.
Best wishes,
Shelley