VALIDATION OF STERILIZING PROCESS
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Transcript VALIDATION OF STERILIZING PROCESS
VALIDATION OF
MOIST HEAT STEILIZATION
JM Tech.
Do-Young Ahn
2015-07-16
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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 121.1°C delivered to a container or
unit of product calculated using a z-value of 10°C.
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 15~20 mmHg, apply for 8~10 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 15~20 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
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