Guide to validation of terminal sterilization process of drugs (GUI-0074): Phase 2, process performance qualification 

Ensure performance qualification (PQ) shows that the process can be reproduced. PQ should include consecutive successful runs (where specified acceptance criteria are met throughout the load for the duration of the proposed routine process specification). Determine the number of required runs using a quality risk management approach.

Loads used for PQ should represent products routinely sterilized, including the most challenging routine loads.

On this page

• Equipment
• Sterilization indicators
• Microbial performance qualification (MPQ)
• Sterilization process interruptions

Equipment

Ensure that:

• the range, resolution, accuracy, reproducibility and response time of all controlling, monitoring and recording equipment can demonstrate that defined process conditions are met
• any failure in control function does not lead to a failure in recording the process parameters, making an ineffective process appear effective (fail-safe feature)
• the standards you use for calibration follow an appropriate standard
  • document and keep records of equipment calibration
• measuring equipment is adequately calibrated and qualified
  • includes all measuring equipment used in analytical methods and the measurement of process parameters for operating the sterilization process

Note: Control instruments should be independent of monitoring instruments and recording charts.

Before you do a validation study, you must make sure the equipment is appropriately qualified for its intended use. More guidance on equipment qualification is available in Guide to validation: Drugs and supporting activities (GUI-0029).

Sterilization indicators

Clearly label each basket, tray or other carrier and indicate whether it has been processed. You may use physical/chemical indicators or a validated electronic product track and trace systems to distinguish between processed and unprocessed goods. These devices indicate exposure to certain sterilization conditions by a visible change, but do not indicate that the load is sterile.

You must:

• use calibrated sterilization indicators or dosimeters in validation studies and requalification, where applicable
  • confirm the supplier's certificate indicates that performance criteria have been met before using the sterilization indicator in validation studies
  • ensure sterilization indicators are appropriately stored and used before they expire
  • ensure detailed written test procedures and records of test results are available
• ensure that data demonstrating adequate pre-determined response to both time and exposure for physical and chemical indicators is available
• test biological indicators for viability and quantification of the challenge organism for indicators obtained commercially
  • test biological indicators prepared in-house for D-value, z-value (moist heat only) and survival/kill time
• ensure a certificate of testing for each lot is available for commercial biological indicators (indicating the population, expiration, D-value and z-value (moist heat only) of the lot)
  • the quantification is acceptable if a biological indicator count provided by the manufacturer has been qualified and periodically confirmed, as per written procedures
• when qualifying commercial or in-house biological indicators, ensure that you choose the media (such as pH, electrolytes, carbohydrates) and sample carriers (such as suspension in ampoules, paper strips, inoculated products and inoculation on solid carriers) based on the BI supplier's recommendations
  • ensure they're consistent with the materials used to validate the terminal sterilization process

Microbial performance qualification (MPQ)

Biological challenge reduction studies for moist heat and ethylene oxide sterilization

Biological challenge reduction studies demonstrate that the sterilization processes will effectively reduce microbial levels to required sterility assurance levels. These studies are required for :

• Phase 1
  • to establish a process and assure it is reliable and effective
• Phase 2
  • to demonstrate the terminal sterilization process can consistently meet requirements

You should:

• consider the product/material bioburden profile over multiple lots of product/material fabricated at different times of the year when choosing the level of biological challenge for the study.
  • consider the type and resistance of the surviving microorganism recovered (will allow you to capture possible seasonal changes)
• implement a worst-case bioburden challenge using an appropriate organism described in Table 1 or another BI organism that demonstrates a greater D-value than the product bioburden
  • in all other cases, use the microorganism with the highest D-value occurring in the natural population (determined by sampling the environment) and provide a scientific justification for your choice
• assess the sterilization process by introducing a known quantity of challenge microorganisms (for example, BI or product bioburden) with established D-values and by assessing the level of reduction over time
  • confirm the sterilization process will deliver a probability of survival of less than 1 in 10⁶ in all cases.

Note: The D-value of the chosen organism must be assessed along with the material to be sterilized and its formulation. This is because resistance of the microorganism can change with changes to parameters such as pH.

For more information, consult the section on the F₀ and D-value.

Table 1: Organisms for biological challenges

Sterilization method	Recommended organism
Moist heat	Geobacillus stearothermophilus
Ethylene oxide	Bacillus atrophaeus

Note: The use of prions (infectious proteins) is not currently recommended to validate moist heat sterilization cycles. The detection and quantification of prions, which is based on animal models, is complex. Also, these proteins may be resistant to moist heat sterilization. They could present a danger if they are accidentally spread in a manufacturing facility.

You should:

• run positive controls for each biological indicator tested with every load to verify the viability of the challenge organism and ensure that viable microorganisms can be detected by the recovery method
• define the placement of biological challenges
  • should be located as close as possible to worst-case locations and next to any sensors (if run alone with distribution studies/penetration studies, refer to Process validation, sterilization by moist heat)
  • should be in containers wherever possible or within process challenge devices (PCDs) to reflect the desired processing conditions
• determine the number of cycles for each load configuration under evaluation based on a documented risk assessment as well as knowledge of the process and operations
  • bracketing strategies may apply to intermediate loads
• conduct robustness studies by changing 1 or more process variables (such as temperature, humidity) and comparing them to the set points used in routine sterilization (below or at minimum levels specified for routine control)
• document and keep records of the biological challenge reduction studies, including:
  • the placement of the biological challenge
  • organism type and name
  • D-value
  • challenge level
  • lot number
  • placement
  • growth result

Sterilization process interruptions

You may need to interrupt the sterilization process for mechanical, safety or operational reasons. For affected products/materials capable of sustaining microbial growth, define the impact of any such interruptions and the maximum length of time allowed for an interruption.

Proper procedures must be in place to direct the operator to the appropriate person to contact if the sterilization process is interrupted or delayed at any point. Investigate any process interruptions.