21 CFR 211.72 - Filters

What it says

Filters for liquid filtration used in the manufacture, processing or packing of injectable drug products must not release fibres into the product, and any use of an asbestos-containing filter must be followed by a second non-fibre-releasing filter, with filter integrity testing performed before and after use for sterilising filtration.

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

What it means in practice

• Pre-use and post-use filter integrity testing together form the evidentiary basis that a sterilising filtration step actually achieved sterility for that specific batch, not simply that the filter was rated appropriately.
• Post-use integrity testing specifically is what confirms the filter did not fail or degrade during the actual filtration run, which pre-use testing alone cannot demonstrate.
• Filter compatibility with the specific product being filtered must be validated, since a filter appropriate for one formulation may interact differently with another.

What FDA inspectors look for

• Whether both pre-use and post-use filter integrity test results are documented for every batch relying on sterilising filtration, not just pre-use testing.
• Whether filter validation data reflects the specific product and process conditions actually used, rather than generic filter manufacturer specifications.
• Whether a failed post-use integrity test triggers a documented investigation into potential impact on the batch's sterility assurance.

Related regulations