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B. Amsden CHEE 440
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
Viruses
B. Amsden CHEE 440
Bacteria
B. Amsden CHEE 440
Bacterial Endospores
B. Amsden CHEE 440
Yeast and Mould
B. Amsden CHEE 440
aspergillus penicillium
B. Amsden CHEE 440
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
B. Amsden CHEE 440
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 heatcell type resistance
bacterial endospores may survive hours inboiling water
fungal spores death at > 80 C in 60min.
yeasts survive 20 min at 60C
bacteria D60 = 1-5 min
viruses
protozoa, algae
rarely survive > 30 minat 60 Crapidly die at T > 40 C
B. Amsden CHEE 440
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
B. Amsden CHEE 440
Sterilization Methods
Filtration used for heat sensitive solutions pore sizes range from 14 to 0.025 m
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
B. Amsden CHEE 440
Kinetics of Cell Inactivation
death rate follows first order kinetics
N t =N0e−kt
B. Amsden CHEE 440
D value
• decimal reduction time• time required for 90% reduction in
cell count
B. Amsden CHEE 440
Z value
degrees of temperature/dose change required to achieve a tenfold decrease in D
B. Amsden CHEE 440
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.
B. Amsden CHEE 440
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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