In an aseptic process two sterilisation steps are of importance for heat labile products; bioburden reduction prefiltration and final sterilising filtration.
The integrity of the final sterilising filter should be verified by integrity testing before use (Pre-Use Post Sterilisation Integrity Test – PUPSIT), to check for damage and loss of integrity caused by the filter preparation prior to use. This verification should also be performed post-use, to detect any filter leaks or perforations that might have occurred during the filtration.
Ideally, the aseptic process is designed to enable in-place filter integrity testing, preferably as a closed system, both before use and post-use. In practice, pre-use testing of a sterilized filter remains debatable for the risks associated in its execution, or may not always be possible due to process constraints (e.g. very small volumes of solution). In these cases, regulatory bodies accept an alternative approach providing a thorough risk assessment has been performed and compliance is achieved by the implementation of appropriate controls to mitigate any risk of a non-integral filtration system.
This risk assessment should take into account at least the sterilisation method and its controls, supply chain, and the aseptic process design and product characteristics to ensure a proper justification for not performing the PUPSIT.
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