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RxNorm codes missing in concept ancestor table

I have isolated all valid/current RxNorm concepts CONCEPT table and have joined it with the ANCESTORS table in order to find their ingredients. This has worked for the majority of valid concepts. However, there are concepts that could not be mapped into ingredients becase their entries are missing in the ANCESTORS table.

See below 2 missing concepts. Note that they do have ingredients concepts (From RxNav).

46274502      1307662        anhydrous lactose        6211        lactose
46274497      1314368        medronic acid            1358207     medronate

Despite the drugs above have ingredients as per RxNav, they do not have any entries in ANCESTORS table (not as ancestor nor descendant), therefore I cannot find their ingredients. I have 15,000 concepts in the same situation. What am I missing? Any help is appreciated.

Note: Most of these missing RxNorm concepts have concept_class ‘Precise Ingredient’ and ‘Brand Name’

The forum suggests that this is the first time you posted something, so welcome to the community! :slight_smile:
Precise ingredients and Brand Names are non-standard, so they do not participate in the hierarchy. You can find their ingredients by following the links “Maps to” and “Brand name of” (+ limiting concept_id_2 to ingredient class) respectively.

Thanks for the welcoming! :smiley: Understood, thanks for the clarification and input.