VALIDATION OF MOIST HEAT STEILIZATION

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VALIDATION OF MOIST HEAT STEILIZATION

• JM Tech.
• Do-Young Ahn

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Definition

• ? Sterilization
• The act or process, physical or chemical, that
  destroys or eliminates all viable microbes
  including resistant bacterial spores from a fluid
  or a solid.
• Examples of sterilization methods are steam
  treatment at 121?, dry heat at 230?, flushing
  with a sterilizing solution such as hydrogen
  peroxide (H2O2) or ozone (O3), irradiation, and
  filtration.
• ?Sterility
• The reduction of anticipated levels of
  contamination in a load to the point where the
  probability of survival is less than 10-6.

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Definition

• ?D-value
• The time in minutes required for a one-log or
  90 reduction of a specific microbial population
  under specified lethal conditions. For steam
  sterilization it is determined at a constant
  temperature
• ?z-value
• The number of degree of temperature change
  necessary to change the D-value by a factor of
  10.

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Definition

• ?F value(lethal rate, instantaneous Fo)
• The F value is a measurement of sterilization
  effectiveness. F(T,z) is defined as the
  equivalent time at temperature T delivered to a
  container or unit of product for the purpose of
  sterilization, calculated using a specific value
  of z.
• ?Fo value(accumulated Fo)
• The term "Fo " is defined as the number of
  equivalent minutes of steam sterilization at
  temperature 121.1C delivered to a container or
  unit of product calculated using a z-value of
  10C.
• Fo ? 10((121-T)/z)?t

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Methodology

• ?Overkill Sterilization
• ?Provides a minimum 12 log reduction of a
  resistant BI w/ a known D-value of not less than
  1 minute.
• ?Required minimal information on the bioburden
• ?Bioburden/Bioindicator Sterilization
• ?Provides a probability of survival of less than
  1 in 106 for the bioburden as demonstrated using
  a resistant BI w/ a known D-value.
• ?BI may not be inactivated
• ?Requires information on the numbers and heat
  resistance of the BI.
• ?Requires ongoing monitoring or control over
  bioburden.

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Methodology

• ?Bioburden Sterilization
• ?Provides a probability of survival of less than
  1 in 106 for the most resistance bioburden
  expected in the load.
• ?Requires information on the numbers and heat
  resistance of the BI.
• ?Requires ongoing monitoring or control over
  bioburden.

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Sterilizer Cycle

• ?Gravity Displacement
• ?Difference of density
• Density of air at 20? 1.2 g/l
• Density of steam at 100? 0.6 g/l
• ?Effectiveness of air elimination depends on the
  rate of steam supply
• Air pocket too rapidly
• Diffusion into the steam too slowly, more
  difficult to remove
• ?Specially designed steam trap permitting the
  passage of large volume of air

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Sterilizer Cycle

• ?Prevacuum cycle
• ?A more effective method
• ?By means of a mechanical vacuum pump or a steam
  eductor
• ?Vacuum as low as 1520 mmHg, apply for 810 min.
• ?Pulsing cycle
• ?A series of alternating steam pulses followed by
  vacuum excursions
• ?Air-steam mixture
• ?Terminal sterilization of large volume
  parenterals
• ?Air injection required to compensate the great
  expansion of air or nitrogen in the head space
  above the liquid
• ?Well mixed chamber fan, raining effect by
  external pump w/ cooling

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Cycle Development

• ?Consider factors into account
• ?Nature of the load porous materials, heat
  sensitivity of the products
• ?Type of the sterilizer
• ?Employed containers and closures
• ?Heat stable product overkill approach
• ?Heat liable product bioburden approach
• Bioburden studies number of microorganisms
• D-value studies only highly resistant spore
  formers,
• BIER(biological indicator evaluator
  resistometer)
• Inoculate the spore into the actual solutions
• For solid materials, precut strips

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Preparing for Validation

• ?Temperature sensing devices
• ? T type thermocouples(copper-constantan)
  encased in flexible sheaths
• ? Premium grades of wire having ?0.1? accuracy
• ?Temperature standards
• ? RTD traceable to the National Bureau of
  Standards , IPR, HTR
• ?Calibration of thermocouples
• ?At two temperatures 0 ?, 130 ?
• ?Correction factors
• ?Stability ?0.03?
• ?Accuracy ?0.5?

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Preparing for Validation

• ?Autoclave
• ?Validation nozzle and adaptor
• ?Data logger digital output and multi-channel
  device
• ?BIs or biological challenges
• ?Loads

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Validation Protocol

• Protocol should include
• ?Objectives of the validation
• ?Responsibilities of validation personnel and
  operating department personnel
• ?Identification and description of the sterilizer
  and its process control
• ?Identification of SOPs equipment
• ?Calibration of instrument SOPs and/or
  description
• ?Identification and calibration of the
  temperature monitoring equipment

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Validation Protocol

• ?A description of the following studies
• ?Bioburden determination studies(if applicable)
• ?Empty chamber heat distribution studies
• ?Container mapping studies(if applicable)
• ?Loaded chamber heat penetration studies
• ?Microbiological challenge studies
• ?Evaluation of drug product cooling water(if
  applicable)
• ?Integrity testing of vent filter
• ?Acceptance criteria
• ?References
• ?Review and approval

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Heat Distribution Studies

• ?To demonstrate the temperature uniformity and
  stability of the sterilizing medium throughout
  the sterilizer
• ?Conduct on both the empty and loaded chamber
  with max. and min. load configurations
• ?Acceptance criteria Less than 1?of the mean
  temperature
• ?Conduct 3 runs to obtain consistent results
• ?Distribution of the thermocouples geometrical
  representatives, exhaust drain, adjacent to the
  control sensor
• ?At least 10 probes, normally 1520 probes

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Heat Distribution Studies

• ?At loaded chamber heat distribution test, the
  thermocouples should be positioned in the same
  locations used for empty chamber heat
  distribution
• ?Avoid contacting solid surfaces
• ?Do not place within any containers
• ?Data should be obtained at regular intervals

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Container Mapping

• ?To determine the coolest point within the liquid
  filled container
• ?Temperature mapping should be conducted on all
  the different container types, sizes and fill
  volume to be validated
• ?The number of the thermocouples used depends on
  the container volume
• ?Possible to use a single thermocouple at
  different positions,
• and can be conducted in a smaller autoclave or
  retort
• ?Penetration thermocouples should be positioned
  at the cold spot having lowest temperature or Fo

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Heat Penetration Studies

• ?To determine the coolest point(s) within the
  specified load and configuration, and to assure
  that these points be consistently exposed to
  sufficient heat lethality
• ?Prior to conduct heat penetration studies,
  determine max. and min. load configurations
• ?Probed container at the cold spot should be
  distributed uniformly throughout the load
• ?Penetration thermocouple are positioned at
  points within the process equipment suspected to
  be the most difficult for steam heat penetration

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Heat Penetration Studies

• ?Lethal rate can be determined from the
  temperature data
• by the following formula
• L log-1(To-Tb)/z 10((To-Tb)/z)
• ?A summation over time of the lethal rate at a
  series of temperature(accumulated lethality)
• Fo ? 10((121-T)/z)?t
• ?Regard to product stability

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Microbial Challenge Studies

• ?Biological challenges are employed during heat
  penetration studies in order to demonstrate the
  degree of process lethality provided by the
  sterilization cycle
• ?Microorganism frequently utilized
• ?Overkill Bacillus stearothermophilus and
  Clostridium sporogenes
• ?Bioburden Calibrated BIs from environmental
  and process
• isolates such as E. coli
• ?Type of BI
• Spore strips or spore suspension into the
  suspending medium
• ?Microbial challenge studies are conducted
  concurrently with the heat penetration studies

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Validation Report

• ?Common elements of all reports
• ?Identification of the task report by number
• ?Reference to protocol
• ?A brief summary of the range of operational
  conditions experienced and how they were
  controlled
• ?A procedure for maintaining control within the
  approved range
• ?A summary and analysis of the experimental
  results
• ?A brief description of any deviation
• ?Conclusion
• ?Review and approval
• ?Cycle development reports are not usually a part
  of the validation report

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Maintenance of Validation

• ?A routine calibration program for all
  instruments critical to the operation of the
  sterilizer and its support system
• ?A preventative maintenance program including
  periodic operational rechecks and comparison to
  OQ record
• ?Routine monitoring of bioburden and periodic BI
  challenges(optionally)
• ?Operating records and equipment logs
• ?Process and equipment change control procedures
  including review to establish whether additional
  validations are required
• ?On-going validation

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Controversial Issues

• ?Incubation of the sterility test 7 days vs. 14
  days
• ?USP provide information concerning critical
  parameters for Parameteric Release
• ?Reduction extent and frequency of revalidation
• ?Verification of D-value of BIs
• ?Use of alternative to B. stearothermophilus as a
  BI