Pharmacopoeial Discussion Group
The four pharmacopoeias — European, Indian, Japanese and US — harmonising general chapters and excipient monographs so one test gives the same accept/reject decision under each. Formed in 1989; IPC joined in October 2023; WHO observes.
What this page does not claim
SPEQ curates and cross-references these bodies. It is not affiliated with, accredited by, or endorsed by any of them, and a count of decoded standards is a measure of SPEQ’s coverage, not of a body’s importance.
WHAT PDG COVERS
The Pharmacopoeial Discussion Group (PDG) is the forum in which the major pharmacopoeias harmonise their texts. It was formed in 1989 by the European Directorate for the Quality of Medicines & HealthCare (for the European Pharmacopoeia), the United States Pharmacopeial Convention, and the Japanese Pharmacopoeia of the Ministry of Health, Labour and Welfare. The World Health Organization has taken part as an observer since May 2001, and in October 2023 the Indian Pharmacopoeia Commission joined as the fourth member. PDG works on general chapters and excipient monographs — the procedures and acceptance criteria that would otherwise force a manufacturer to test the same material three or four different ways. It has no website of its own; its policy, working procedure, meeting highlights and signed-off texts are published by its members, including PMDA for the Japanese Pharmacopoeia.
WHAT PDG PUBLISHES
- 01Statement of Harmonisation Policy (revision October 2023) — the definition of "harmonised" and the commitment not to revise harmonised texts unilaterally
- 02Working Procedure of the PDG (revised version 6, October 2025) — the Pre-PDG and Stage 1–5 process and the sign-off rules
- 03Sign-off documents and cover sheets for each harmonised general chapter and excipient monograph, listing harmonised provisions and non-harmonised parts
- 04Stage 2 drafts for official inquiry, published in each member pharmacopoeia's forum
- 05Meeting highlights and the work programme, published by member pharmacopoeias
HOW ITS REQUIREMENTS BITE
PDG has no legal force of its own. A harmonised text is drafted by a coordinating pharmacopoeia, published for comment in each pharmacopoeia's forum at Stage 2, agreed and signed off at Stage 3, then adopted by each pharmacopoeia under its own procedure at Stage 4. Only that adoption makes it official, and each pharmacopoeia sets its own implementation date. Harmonisation is achieved, by PDG's own definition, when the text is official in all the pharmacopoeias. Where full harmonisation is not possible, PDG harmonises by attribute and records the remainder as non-harmonised parts on the sign-off cover sheet.
What practitioners get wrong
- "Harmonised" is a claim about one chapter and one cover sheet, not about the pharmacopoeias in general. A "–" against a pharmacopoeia, or a listed non-harmonised part, is exactly where interchangeability stops.
- Sign-off is not implementation. The same signed-off text can be official in one pharmacopoeia and pending in another, so a multi-region specification must track each region's date.
- Each pharmacopoeia flags its own residual differences in the published text with black diamonds — check for them before claiming one test serves every market.
- Regulatory interchangeability is a separate step: ICH Q4B annexes cover 16 PDG-harmonised texts, and PDG now maintains those annexes for ICH.
WHERE IT SITS INTERNATIONALLY
PDG sits beside ICH rather than inside it. Under its harmonisation policy PDG maintains the 14 annexes of ICH Q4B, which give regulatory interchangeability for 16 PDG-harmonised texts, and submits revised annexes to ICH. Since the January 2025 revision of the working procedure, signed-off texts are also shared with other world pharmacopoeias through the International Meeting of World Pharmacopoeias contact list. The member compendia remain separately binding in their own territories.
PDG STANDARDS SPEQ DECODES · 1
DISCIPLINES IN PDG’S REMIT
PDG: frequently asked questions
Reference answers on Pharmacopoeial Discussion Group’s mandate, what it publishes, and how its requirements acquire force.
Who are the members of the Pharmacopoeial Discussion Group?
The European Pharmacopoeia (EDQM), the Indian Pharmacopoeia Commission, the Japanese Pharmacopoeia and the United States Pharmacopeia. PDG was formed in 1989 by the European, Japanese and US pharmacopoeias; WHO has been an observer since May 2001, and the Indian Pharmacopoeia Commission joined in October 2023.
What does it mean for a pharmacopoeial text to be harmonised by PDG?
PDG defines a text as harmonised when a substance tested by the harmonised procedure yields the same results and the same accept/reject decision. Harmonisation is achieved when the text has become official in all PDG pharmacopoeias; where full harmonisation is not possible, residual differences are listed as non-harmonised parts on the sign-off cover sheet.
What are the stages of the PDG harmonisation process?
After a Pre-PDG concept stage, Stage 1 is the first draft, Stage 2 the official inquiry published in each pharmacopoeia's forum, Stage 3 consensus and sign-off, Stage 4 regional adoption and implementation, and Stage 5 inter-regional acceptance for chapters evaluated under ICH Q4B. The current working procedure is revised version 6, October 2025.