Filter fluid interaction studies involve physico-chemical compatibility, extractable and adsorption studies.

Physico-chemical Compatibility

Compatibility is determined by performing the following tests both prior to and after the worst case exposure:

• Integrity test results using the reference fluid
• Flow Rates
• Membrane Thickness
• Weight of the membrane

The filter is exposed to the process fluid for a specified period under pre-determined conditions that include, exposure times exceeding the maximum process time and temperature exceeding maximum process temperature.

Extractable Studies

• Extractable studies are conducted based on the model solvent approach, defined by PDA Technical report 26, 2008. Model solvent streams are selected based on the component profile of the drug product and the studies are conducted under simulated worst case process conditions.
• These studies involve extract preparation with process scale filters, representing the sterilizing filters used in the drug manufacturing process, in terms of design and materials of construction.

Adsorption Studies

• It is critical that filters are selected to minimize adsorption and loss of product components. Laboratory-scale filter tests are used to generate adsorption profiles to help with filter selections and process qualification.
• Process conditions such as temperature and filter fluid contact time (flow rates) are simulated as these may have an impact on adsorption.