ICH Q8(R2) vs ICH Q11
Quality by Design for the drug product vs for the drug substance.
What a comparison is not
A comparison is SPEQ’s reading of how two published documents differ. Neither is the right answer, it is not a determination of which applies to you, and neither is summarised in a way that replaces reading it.
ICH Q8 and ICH Q11 both apply Quality by Design (QbD), but to different parts of the product. Q8 covers pharmaceutical development of the drug product — the formulation and process that make the finished dosage form. Q11 extends the same QbD concepts to the drug substance (the API). They share the vocabulary of QTPP, CQAs, design space, and control strategy, applied to different objects.
| ASPECT | ICH Q8(R2) | ICH Q11 |
|---|---|---|
| Object | The drug product (finished dosage form) | The drug substance (API) |
| Shared concepts | QTPP, CQAs, design space, control strategy | Same QbD concepts, applied to the substance |
| Starting point | Formulation and manufacturing process design | Selecting starting materials and the synthetic route |
| Key extra topic | Excipient and formulation variables | Starting-material justification; both approaches (traditional & enhanced) |
| Output | Product control strategy and (optional) design space | Substance control strategy and (optional) design space |
| Relationship | Foundational QbD guideline | Extends Q8 QbD to the API; used with Q9/Q10 |
Use ICH Q8 for developing the finished drug product — formulation, dosage-form process, and the product control strategy.
Use ICH Q11 for developing and justifying the drug substance — the synthetic route, starting-material selection, and the substance control strategy.
Same QbD toolkit, two objects: Q8 for the product, Q11 for the substance. They are not alternatives — a full development programme applies Q8 to the dosage form and Q11 to the API, both underpinned by Q9 risk management and living in a Q10 quality system. The distinctive Q11 question is justifying starting materials; the distinctive Q8 question is formulation.
ICH Q8(R2) vs ICH Q11: frequently asked questions
Common questions on how ICH Q8(R2) and ICH Q11 differ and when each applies.
What is the difference between ICH Q8 and Q11?
ICH Q8 covers Quality by Design for the drug product (formulation and dosage-form process); ICH Q11 applies the same QbD concepts to the drug substance (API), including selecting the synthetic route and justifying starting materials. Same methodology, different object.
Do Q8 and Q11 require a design space?
No. A design space is one optional QbD element in both. You can develop a product or substance with a traditional approach or an enhanced (QbD) approach; a formal design space is not mandatory under either guideline.
How do Q8/Q11 relate to Q9 and Q10?
Q8 and Q11 are the development guidelines; Q9 provides the risk-management methodology that supports development decisions; Q10 is the quality system in which the resulting control strategy operates across the lifecycle. They form an integrated set.
What is a control strategy?
A planned set of controls — derived from product and process understanding — that assures process performance and product quality. Both Q8 (product) and Q11 (substance) culminate in a control strategy, whether developed traditionally or through enhanced QbD.