When mapping a drug from your local formulary to RxNorm, you may come across two different RxNorm drug concepts with the same ingredient, strength, form and route. Which RxNorm concept you choose depends on how you will be using the drug data. As a rule, RxNorm normalizes their generic drug concepts to consist of ingredient, strength, and dose form (which may include route of administration), but there may be certain instances, depending on use case, where two drugs may need to be distinguished even though they don’t differ based on the ingredient, strength, or routed dose form.
RxNorm has a new quasi-attribute in their terminology model, called Qualitative Distinction. This sounds rather ambiguous and it is. There was a need to “add flexibility” to the drug model, so a level of granularity was added to distinguish certain drug concepts from other concepts that are essentially the same. As an example, RxNorm now can differentiate between two Bupropion drug concepts having the same ingredient, strength or routed dose form with the addition of the terms Smoking Cessation as a Qualitative Distinction. This distinguishes it from the otherwise identical drug concept which might be intended as an antidepressant. Note that Qualitative Distinction is added to the front of the string value (prefix), thus could look a little peculiar in some cases, such as for drugs that include the Food and Drug Administration (FDA) New Drug Application (NDA) moniker in the string, like NDA019430 0.3 ML Epinephrine 1 MG/ML Auto-Injector [Epipen].
Here are several examples of how the Qualitative Distinction attribute is used:
• Abuse-Deterrent 12 HR Oxycodone Hydrochloride 15 MG Extended Release Oral Tablet [Oxycontin] is a different RxNorm drug concept from Oxycodone Hydrochloride 15 MG Extended Release Oral Tablet [Oxycontin]
• Smoking Cessation 12 HR Bupropion Hydrochloride 150 MG Extended Release Oral Tablet [Zyban] is a different RxNorm drug concept from Bupropion Hydrochloride 150 MG Extended Release Oral Tablet [Zyban]
• NDA019430 0.3 ML Epinephrine 1 MG/ML Auto-Injector [Epipen] is a distinct drug concept from Epinephrine 1 MG/ML Auto-Injector [Epipen]
As of November, 2017, there are only 25 Qualitative Distinctions (listed below), but the list is growing. 
0.5 UNT Doses
30/70 Release
3-Bead
3-Month
40/60 Release
4-Month
50/50 Release
Abuse-Deterrent
Atrial Fibrillation
Augmented
Biphasic
Emollient
Matrix Delivery
Microencapsulated
Modified
NDA019430
NDA020800
NDA201739
Once-Daily
Osmotic
Preservative-Free
Smoking Cessation
Soft Gelatin
Sprinkle
Sugar-Free
The HDD has had a similar attribute, called Clinical Drug Modifier, since many years ago, as we recognized the need for this distinguishing characteristic when we map our customers’ formulary items into the HDD. There are similar members between the HDD’s modifier attribute and RxNorm’s Qualitative Distinction attribute, for example, “preservative free” and “sugar free”. However, other RxNorm Qualitative Distinctions would be captured by additional, new HDD concepts within one of the core attributes of ingredient, strength, route and form, wherever appropriate (e.g., sprinkle), and clinical intent such as Atrial Fibrillation or Smoking Cessation would more likely be captured using relationships to other concepts. Nevertheless, awareness of the Qualitative Distinction attribute may be of help when you are standardizing to RxNorm.
If you have questions or would like assistance with RxNorm implementation or mapping, please contact us.