## PharmTech Poll Results: How do you define 'design space'?

Oct 23, 2007
By Pharmaceutical Technology Editors
Untitled Document

PharmTech Poll Results: How do you define ‘design space’?

Thanks to all of you who participated in our poll! Here are a few of your answers, followed by the definition of ‘design space’ given by the FDA.

1. “The multidimensional ‘space’ is defined by the extreme combinations of all operating parameters for process, equipment, and facilities. Narrow design space by identifying critical (direct impact) or key (indirect impact) parameters on critical to quality product attributes.”

2. “The mathematical and statistical equations defining the combination of independent factor space and dependent response space from designed experiments that results in a system, product or process that consistently meets its quality characteristics with a high degree of assurance.”

3. “I think ‘design space’ is just a new buzz word for defining the acceptable range of a product and process, which is something an optimization program should have done for many years now.”

4. “The multidimensional combination and interaction of input variables (e.g., material attributes) and process parameters associated with a high probability of the critical quality attributes all meeting specification. Mathematically, it is: Design Space={x such that Prob(Y is in S given x) is at least some acceptable reliability value}, where Y is a vector of critical quality attributes, S is a multidimensional specification region, and x is a vector of controllable process parameters. See Peterson, J. J. (2004) Journal of Quality Technology, 139-153, Figure 6.”

According to FDA

FDA defines design space in its Guidance for Industry Q8: Pharmaceutical Development, as:

“The multidimensional combination and interaction of input variables (e.g., material attributes) and process parameters that have been demonstrated to provide assurance of quality. Working within the design space is not considered as a change. Movement out of the design space is considered to be a change and would normally initiate a regulatory postapproval change process. Design space is proposed by the applicant and is subject to regulatory assessment and approval.” The guidance is available here.