FDA Guidance for Drugs: Bracketing and Matrixing

  • FDA Guidance for Drugs: Bracketing and Matrixing

    Posted by David Taylor on October 25, 2022 at 1:45 pm

    What is Matrixing in Drugs?

    This guidance is intended to address recommendations on the application of bracketing and matrixing to stability studies conducted in accordance with the principles outlined in the ICH guidance Q1A(R) Stability Testing of New Drug Substances and Products (the parent guidance).


    The design of a stability schedule such that only samples on the extremes of certain design factors (e.g., strength and package size) are tested at all time points as in a full design. The design assumes that the stability of any intermediate levels is represented by the stability of the extremes tested.

    For example, this indicates that for a product with three different strengths, say tablets at 2, 4 and 6 mg, it may be possible to omit testing of the 4 mg tablets.


    The design of a stability schedule such that a selected subset of the total number of possible samples for all factor combinations is tested at a specified time point. At a subsequent time point, another subset of samples for all factor combinations is tested. The design assumes that the stability of each subset of samples tested represents the stability of all samples at a given time point.

    Therefore, at a given time point (other than the initial or final ones) not every batch on stability needs to be tested.

    The ICH Guideline for Stability Testing:

    Stability testing is a vital part of product development. It is, however, quite resource consuming and, with 12 months’ stability data generally required for a new product licence, is also often on the critical path of development. Therefore, it is vital that stability protocols are designed both properly, to ensure regulatory approval, and efficiently to minimize the time and resources required.

    FDA Guidance for Industry: Bracketing and Matrixing

    Fortunately, there are well-accepted procedures, namely bracketing and matrixing (B&M), to reduce the amount of stability testing required. These are procedures for reducing the number of samples of product tested for stability which, when correctly applied, should result in neither loss of data quality produced nor a significant change in the predicted shelf life. Such procedures are also theoretically applicable to drug substances, but, as there tend to be fewer presentations or batches tested than for products, the opportunities and benefits are more restricted.


    Stability samples must be manufactured, labelled and stored, so reducing the number of stability samples can also potentially save in sample production and management costs, especially since storage facilities are quite expensive to set-up and maintain.

    David Taylor replied 1 year, 8 months ago 1 Member · 0 Replies
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