Transcript STERILITY

STERILIZATION
The complete destruction of all living organisms and their spores or
their complete removal from the formulation.
All parenterals, as well as otic, nasal, ophthalmic solutions, must be
sterile,
 includes packaging materials
methods
 steam
 dry-heat
 filtration
 gas
 ionizing radiation
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Viruses
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Bacteria
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Bacterial Endospores
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Yeast and Mould
aspergillus
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penicillium
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Sterilization Methods
steam sterilization
 conducted in an autoclave
 method of choice
 121 C, 20 minutes
dry heat
 less effective than moist heat
 170 C, > 2 hours
 used to sterilize equipment
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Heat Resistances
 method determined by nature of micro-organism and
formulation ingredients
 protocols are developed based on reference organisms of
known sterilization resistance
micro-organisms possess different resistances to heat
cell type
resistance
bacterial endospores may survive hours in
boili ng water
fungal spores
death at > 80 C in 60
min.
yeasts
survive 20 min at 60C
bacteria
D60 = 1-5 min
viruses
rarely survive > 30 min
at 60 C
rapidly die at T > 40 C
protozoa, algae
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Steam Sterilization
Determination of steam sterilization protocol
 first select a reference organism
 determine its D value under defined conditions
 establish initial bioburden
 calculate time of exposure at 121 ºC
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Sterilization Methods
Filtration
 used for heat sensitive solutions
 pore sizes range from 14 to 0.025 mm
Gas sterilization
 used in hospitals and industry for thermolabile materials
 ethylene oxide, propylene oxide used
 500-1000 mg/L, 4 - 16 hours at 55 ºC, 50-60 %RH
 need to remove absorbed gas after sterilization
Ionization
 use of gamma rays
 limited application
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Kinetics of Cell Inactivation
death rate follows first order kinetics
N t  N0e  kt
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D value
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decimal reduction time
time required for 90% reduction in
cell count
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Z value
degrees of temperature/dose change required to achieve a tenfold
decrease in D
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Example
Using G. stearothermophilus as a reference organism (D121 = 1.5
min), and an initial bioburden of 1000 spores, determine the
sterilization time required to achieve a 1 in 1,000,000 chance of a
spore surviving using a steam autoclave.
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De-pyrogenation
Emphasis is placed on prevention of introduction of pyrogens
Removal
 glassware, metals
• 250 ºC for 45 minutes
 water
• oxidation to nonvolatile solvents using potassium
permanganate, then distill
• reverse osmosis
 plastics
• protect against contamination
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