Hi @Rijnbeek, thanks for raising this - great catch and worth fixing or at least making deterministic and documented.
The route suffixes that appear in ATC class concept names in Athena/ATLAS were introduced in 2020. Before that change, ATC classes surfaced without route/form hints, so users often saw several codes with the same ingredient label and had to leave Athena/ATLAS to cross-check the WHO ATC browser by code. As I know, the intent of adding route hints was usability.
What you are observing now - labels like “ibuprofen; systemic, rectal” - comes from a normalization rule in the ATC ingestion step that maps WHO Adm.R to a succinct suffix. Specifically, O + P (oral + parenteral) is collapsed to “systemic” (because both oral and parenteral routes deliver drug into the bloodstream for body-wide effect). if R is also present, the suffix becomes “systemic, rectal.” That’s why classes with WHO routes O,P,R display as “systemic, rectal,” while O,R classes enumerate “oral, rectal.” Functionally nothing is missing from the source, but the summarization masks which systemic routes are present. Your audit is right that this creates ambiguity.
I see two clean ways forward. Either to remove route hints from names altogether and surface Adm.R only as structured metadata; or, to enumerate them so O,P,R → “oral, parenteral, rectal.” Given how people actually search and build concept sets, my recommendation is the latter: keep the hints but make them explicit and deterministic, and document the rule.
If vocab maintainers agree, the next step is to open an issue proposing (a) publication of the Adm.R→suffix mapping table and (b) adoption of deterministic route labels in the vocabulary’s load_stage scripts, followed by a PR; if ATC is not on the February 2026 roadmap, this can proceed as a community contribution.
Below is a mapping from WHO Adm.R route combinations to OMOP route suffixes for multi-route drugs. These reflect the 2020 implementation, details may have changed since.
| WHO Adm.R | Current OMOP suffix | Proposed explicit suffix (if keeping) |
|---|---|---|
| Chewing gum + Inhal + N + SL + TD | chewing gum, inhalant, nasal, sublingual, transdermal | - |
| implant + N + P | implant, nasal, parenteral | - |
| implant + P | implant, parenteral | - |
| Inh.aerosol + O + P + R + SL | systemic, rectal, sublingual | inhalant, oral, parenteral, rectal, sublingual |
| Inhal + Inhal.powder + Inhal.solution + P | inhalant, parenteral | - |
| Inhal. powder + Inhal.solution + O | inhalant, oral | - |
| lamella + ointment + Opht (S01) | ophthalmic | - |
| N + O | nasal, oral | - |
| N + O + P + R | nasal, systemic, rectal | nasal, oral, parenteral, rectal |
| N + O + P + R + TD + V | nasal, systemic, rectal, transdermal, vaginal | nasal, oral, parenteral, rectal, transdermal, vaginal |
| N + O + P + SL | nasal, systemic, sublingual | nasal, oral, parenteral, sublingual |
| N + P | nasal, parenteral | - |
| N + SL + TD | nasal, sublingual, transdermal | - |
| O (D11AX10) | oral, topical | - |
| O (A01A, A07EA06, R02AA0) | oral, local oral | - |
| O + oral aerosol + SL + TD | oral, oral aerosol, sublingual, transdermal | to check |
| O + P + R | systemic, rectal | oral, parenteral, rectal |
| O + P + R + SL + TD | systemic, rectal, sublingual, transdermal | oral, parenteral, rectal, sublingual, transdermal |
| O + P + R + V | systemic, rectal, vaginal | oral, parenteral, rectal, vaginal |
| O + P + SL | systemic, sublingual | oral, parenteral, sublingual |
| O + P + TD | systemic, transdermal | oral, parenteral, transdermal |
| O + P + V | systemic, vaginal | oral, parenteral, vaginal |
| O + R | oral, rectal | - |
| O + SL | oral, sublingual | to check |
| O + SL | oral, local oral | to check |
| O + TD | oral, transdermal | - |
| O + V | oral, vaginal | - |
| P + SL + TD | parenteral, sublingual, transdermal | - |
| P + urethral | parenteral, urethral | - |
| T (R01A) | inhalant, nasal | - |
| T (S03) | ophthalmic, otic | - |
| T (C05A) | rectal, topical | - |