FDA representatives stated that not all testing or measurements conducted to verify that a finished lot of excipient material complies with its required properties must be performed on samples taken from the finished lot. The representatives do not believe that testing or measurement of in-process materials to verify product quality constitutes skip testing. To ensure that a lot of excipient material complies with its required properties, it is acceptable to rely on tests or measurements conducted on samples of material taken at an in-process stage of production, provided that the in-process material will not be affected by subsequent processing or holding with respect to the attributes being verified. There should be justification that test results or measurements, or product performance characteristics, do not change from the in-process stage to the finished product.

According to FDA representatives, an appropriate determination to ensure that each lot conforms to appropriate specifications could involve some combination of the following approaches:

• End-product testing
• In-process testing
• Continuous monitoring of an attribute with statistical process controls
• Documented rationale that, based on the method of manufacture, the test attribute cannot be present and therefore the test is not applicable (e.g., residual solvents).

Using end-product testing alone requires testing each lot of excipient material for conformance to all specifications. In-process testing might involve the use of an on-line test to determine whether a product attribute meets an appropriate acceptance criterion, provided that the attribute does not change during the subsequent processing steps until the finished excipient is produced. Continuous process monitoring with statistical process controls involves comprehensive testing of an attribute using on-line monitoring and corresponding process and/or product adjustments to prevent lot-to-lot variation in the product. Depending on the product and specification, any of the above approaches might be appropriate for conducting a determination to ensure that each batch of the product conforms to the specification.

The representatives stated for clarity, FDA prefers the term measurement instead of test as it relates to product quality, because measurement conveys the correct idea of analytical testing of material quality using either nondestructive in-line or on-line analytical techniques as well as off-line destructive analysis commonly used today. This approach gives excipient manufacturers more latitude to use various options to verify a given product attribute.

PAT for excipient manufacturing. PAT uses appropriate design, analysis, and control of manufacturing processes, including in-process testing and controls to ensure that a finished drug product is manufactured under appropriate controls. A benefit of using PAT is that finished-product testing can be minimized by a drug-product manufacturer on their final dosage forms. One meeting participant asked, "Why can't these same concepts be applied to excipient testing when the excipient manufacturer applies similar control strategies?" Additional guidance or clarification is needed from the regulatory agency(ies) on these topics.

ICH Q6A applies to drug products, and an official clarification by FDA with a specific guidance for excipients is needed. Alternatively, an industry group such as IPEC-Americas may wish to present industry guidance suitable for self-regulation. Documents in this area are currently being developed by IPEC-Americas.

How characterization of excipient physical and chemical properties helps build quality into the drug product

This topic was described to the participants as follows:
Following the spirit of FDA's 21st Century Pharmaceutical CGMP and Quality by Design (QbD) initiatives, the workshop will explore ways to improve product quality by characterization and control of physical and chemical properties of critical excipients in a given product (8-10).