Sterilization Methods and Filtration Technology Flashcards

What is the minimum membrane filter pore size required to achieve sterilization by filtration of a compounded sterile preparation?

Answer: 0.22 micron

A pore size of ≤0.22 micron (also stated as 0.2 micron) is required for sterilizing-grade filtration because it retains bacteria. Larger pore sizes (0.45 micron) are used for clarification, not sterilization.

What are the standard parameters for terminal sterilization of a preparation by moist heat (autoclave)?

Answer: 121°C for a minimum of 15 minutes at 15 psi

The standard autoclave cycle is 121°C at 15 psi for at least 15 minutes. This combination of temperature and pressure is sufficient to achieve a sterility assurance level (SAL) of 10⁻⁶ for terminally sterilized preparations.

Which sterilization method is MOST appropriate for a heat-sensitive aqueous drug that cannot withstand autoclave temperatures?

Answer: Membrane filtration through a 0.22-micron sterilizing-grade filter

Membrane filtration through a ≤0.22-micron filter is the preferred method for heat-sensitive aqueous preparations. It removes bacteria and fungi without exposing the drug to destructive temperatures. Ethylene oxide is used for devices, and dry heat/radiation are not practical for liquids.

What is 'depyrogenation,' and which method is most commonly used to achieve it on glassware and equipment?

Answer: Removal of endotoxins; dry heat at ≥250°C for at least 30 minutes

Depyrogenation is the destruction or removal of pyrogens (primarily bacterial endotoxins). Endotoxins are heat-stable and survive standard autoclaving; dry heat at ≥250°C for ≥30 minutes is required to destroy them on glassware and stainless steel.

After filtering a compounded sterile preparation through a 0.22-micron membrane filter, a bubble point integrity test is performed. What does this test confirm?

Answer: That the filter membrane is intact and was not compromised during filtration

The bubble point integrity test verifies that the filter membrane has not been punctured, torn, or otherwise compromised. A breached filter could allow microorganisms to pass through, invalidating the sterilization process. USP requires post-filtration integrity testing for high-risk CSPs.

Which of the following BEST describes 'terminal sterilization' as opposed to 'aseptic processing'?

Answer: Sterilizing the final sealed container after filling to achieve a defined sterility assurance level

Terminal sterilization involves sterilizing the product after it has been filled and sealed in its final container (e.g., autoclaving a sealed vial). This is contrasted with aseptic processing, where sterile components are combined under aseptic conditions but the final container is never subjected to a sterilization step.