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The WHO Drug Dictionary is now called WHODrug Global, a standardised medicines terminology maintained by the Uppsala Monitoring Centre (UMC) and used to code the drugs reported in clinical trials and pharmacovigilance. This guide goes past the one-line definition and decodes the drug code itself, using records printed in UMC’s own user guide, so you can read a WHODrug code and know what each part means.
What is the WHO Drug Dictionary?
UMC describes WHODrug Global as “the international reference for medicinal product information”. The user guide calls it “a global and standardised terminology for medicines and vaccines, developed, maintained and distributed by Uppsala Monitoring Centre (UMC), an independent, not-for-profit foundation.” It is used by pharmaceutical companies, contract research organisations, research organisations and regulatory agencies, in clinical trials and pharmacovigilance.
Coverage is broad. UMC states that it covers medicinal product information from nearly 150 countries and includes conventional medicines and herbal remedies, as well as biotech and blood products, diagnostic substances and contrast media. Subscribers receive text and csv files (the csv is UTF-8) or use the browsing tool WHODrug Insight.
WHODrug vs WHODrug Global: is it the same thing?
For current purposes, yes. The user guide states that since 1 March 2017 all WHODrug terminology types are combined into one terminology named WHODrug Global. “WHO Drug Dictionary” is the older, still widely searched name for the same UMC product. A Chinese version was introduced on 1 September 2019.
How a WHODrug drug code is built
In statistics a formula has symbols; in WHODrug the equivalent is the drug code. According to section 6.2 of the user guide, the drug code is “an aggregation of Drug Record Number (DrugRecNo), Sequence number 1 (Seq1) and Sequence number 2 (Seq2)”. It uniquely identifies a drug name and its substance or substances (or an Umbrella record), and it is the unique identifier in the B3 format.
| Part | Length | What it identifies |
|---|---|---|
| DrugRecNo | 6 characters | The substance, or combination of substances, “regardless of variation or plant part”. |
| Seq1 | 2 characters | The variation of the substance. Seq1 = 01 always identifies a specific active substance base or a combination of substance bases; higher values are variations. |
| Seq2 | 3 characters | The name of the record. Seq2 = 001 represents the substance or substance combination; Seq2 above 001 represents product names and substance synonyms. |
Worked example: decoding real WHODrug records
The user guide prints the following records, written as DrugRecNo, Seq1 and Seq2, followed by the drug name.
| DrugRecNo | Seq1 | Seq2 | Drug name |
|---|---|---|---|
| 000200 | 01 | 001 | Paracetamol |
| 006460 | 01 | 001 | Insulin human |
| 132106 | 01 | 001 | Desogestrel;Estradiol |
| 000005 | 01 | 001 | Ampicillin |
| 000005 | 02 | 001 | Ampicillin sodium |
| 000005 | 03 | 001 | Ampicillin trihydrate |
Reading these row by row:
- Paracetamol, 000200 01 001. Seq1 is 01, so the record is the active substance base. Seq2 is 001, so it names the substance itself rather than a product name or synonym.
- Desogestrel;Estradiol, 132106 01 001. One DrugRecNo covers a combination of substances. The record is still Seq1 = 01 because it is a combination of substance bases.
- The ampicillin group, 000005. All three records share one DrugRecNo because they are the same substance. Seq1 moves from 01 (the base) to 02 (sodium) and 03 (trihydrate), the variations. DrugRecNo alone therefore cannot distinguish ampicillin from ampicillin sodium; the full three-part code can.
Reading a code: interpretation guide
| If you see | It means (per the UMC user guide) |
|---|---|
| Seq1 = 01, Seq2 = 001 | The active substance base, or a combination of substance bases, named as the substance. |
| Seq1 above 01, Seq2 = 001 | A variation of the same substance, such as a salt or hydrate, sharing the base’s DrugRecNo. |
| Seq2 above 001 | A product name or a substance synonym. |
| A name ending in a bracketed ingredient, such as CALCIUM [CALCIUM GLUCONATE] | A non-unique name made unique in the B3 format by appending [INGREDIENT(S)]. The generic non-unique name CALCIUM carries no suffix. |
B3 vs C3 format
WHODrug Global is delivered in two formats, B3 and C3. The user guide states that all names in B3 are also in C3, and that since March 2019 the terminology is provided only in the B3 and C3 formats.
| Format | What it carries |
|---|---|
| B3 | Drug names, active substances and ATC classifications. |
| C3 | Everything in B3, plus country of sale, marketing authorisation holder, pharmaceutical form (EphMRA NFC) and strength. C3 also gives a higher precision of ATC code assignment, because each drug name is assigned specific ATC codes. |
UMC also offers an optional add-on, WHODrug Cross Reference ATC 5, for assigning ATC fifth-level codes.
How WHODrug uses ATC codes
The user guide states that “the ATC classification is integrated in WHODrug”. ATC (Anatomical Therapeutic Chemical) is maintained by the WHO Collaborating Centre for Drug Statistics Methodology in Oslo and has five levels under fourteen main groups. The guide’s own example for morphine reads as a path down the hierarchy:
- N: Nervous system
- N02: Analgesics
- N02A: Opioids
- N02AA: Natural opium alkaloids
- N02AA01: Morphine
The WHO Collaborating Centre explains that the single-code principle “allows aggregation of data in drug utilization monitoring and research”. The user guide adds a caution: ATC is mainly used for drug utilisation research and is not primarily intended for identifying all the indications a specific medicinal product might have. See also the defined daily dose (DDD) entry, which belongs to the same WHO ATC/DDD system.
WHODrug vs MedDRA
The two dictionaries answer different questions. WHODrug codes the medicine; MedDRA codes the medical event. The two are compared side by side in the MedDRA coding of trial safety data guide. For where drug coding sits in a wider data workflow, see clinical data management, ICSR processing and data management plans for clinical trials.
Assumptions and common mistakes
- Treating DrugRecNo as the whole code. Salts and hydrates of one substance share a DrugRecNo, as the ampicillin records show. Store and compare all three parts.
- Treating a product name as a substance. Seq2 above 001 is a product name or synonym. Only Seq2 = 001 represents the substance or combination.
- Ignoring the bracketed suffix. In B3, a name like CALCIUM [CALCIUM GLUCONATE] is a different record from the generic CALCIUM. Dropping the bracket merges records that the dictionary keeps apart.
- Reading ATC as an indication list. The user guide says it is not primarily intended for that.
- Not recording the release. The dictionary is updated twice a year, so the version you coded against is part of the result.
How often is WHODrug Global updated?
UMC states that there are new releases twice a year, on 1 March and 1 September. The user guide cited here is the March 2026 edition.
How to cite WHODrug Global
Name the publisher, the product and the release you used, because the content changes twice a year. For example: Uppsala Monitoring Centre. WHODrug Global, March 2026 release. https://who-umc.org/whodrug/whodrug-global/what-is-whodrug-global/. In a trial report or data management plan, state the format (B3 or C3) as well as the release.
FAQ
Who maintains the WHO Drug Dictionary?
The Uppsala Monitoring Centre (UMC), an independent, not-for-profit foundation, develops, maintains and distributes it.
Does WHODrug include herbal products?
Yes. UMC states that it covers both conventional medicines and herbal remedies, together with biotech and blood products, diagnostic substances and contrast media.
What is the difference between B3 and C3?
C3 contains everything in B3 and adds country of sale, marketing authorisation holder, pharmaceutical form and strength, with more precise ATC assignment.
Is WHODrug the same as the ATC classification?
No. ATC is maintained by the WHO Collaborating Centre in Oslo; WHODrug integrates ATC codes alongside its own drug records and drug codes.
How do I read a WHODrug code such as 000005 02 001?
000005 is the DrugRecNo (ampicillin), 02 is the Seq1 variation (ampicillin sodium) and 001 is the Seq2 value that names the substance rather than a product or synonym.
Sources
- Uppsala Monitoring Centre. What is WHODrug Global. https://who-umc.org/whodrug/whodrug-global/what-is-whodrug-global/ (checked 2026-10-29).
- Uppsala Monitoring Centre. WHODrug User Guide, March 2026 (PDF, sections 5.2.1, 6.2 and 10). https://edit.who-umc.org/media/k1wmz52z/whodrug-user-guide-march-2026.pdf (checked 2026-10-29).
- WHO Collaborating Centre for Drug Statistics Methodology. ATC structure and principles. https://atcddd.fhi.no/atc/structure_and_principles/ (checked 2026-10-29).
