ICH Q1D - Bracketing and Matrixing Designs for Stability Testing

What it says

Q1D describes reduced stability designs. Bracketing tests only the extremes of certain design factors, such as strength or container size, on the assumption that the intermediate levels are represented by the extremes. Matrixing tests a selected subset of the total number of possible samples at each time point, with the others tested at later points. Both need justification and are not suitable in every case.

Paraphrased for plain-language clarity. Always verify against the current published regulation text.

What it means in practice

• These designs can lower the number of samples tested, but only if the products are really similar in composition and container closure.
• The rationale must be written and scientifically justified in advance, not applied after the data are in.
• If the data show variability, the reduced design may need to be replaced with a full design.

What inspectors look for

• Whether the reduced design was justified in the protocol.
• Whether the factors bracketed are truly the extremes.
• Whether results support the design or show it was not appropriate.

Related regulations