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STERILITY the complete destruction of all living organisms and their spores or their complete removal from the formulation all parenterals must be sterile, as well as otic, nasal, ophthalmic solutions includes packaging materials methods steam dry-heat filtration gas ionizing radiation
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Sterilization steam sterilization dry heat
method determined by nature of micro-organism and formulation ingredients protocols are developed based on reference organisms of known sterilization resistance 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 micro-organisms possess different resistances to heat
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Filtration used for heat sensitive solutions
pore sizes range from 14 to mm advantages fast for small volumes effective for thermolabile materials inexpensive removes other particulate matter disadvantages possibility of tears in membrane comparatively slow for large volumes
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Sterilization Methods
Gas sterilization used in hospitals and industry for thermolabile materials ethylene oxide, propylene oxide used mg/L, hours at 55 ºC, %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 guaranteed sterility would require an infinite time D value decimal reduction time time required for 90% reduction in cell count Z value degrees of T change required to achieve a tenfold decrease in D
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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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Example Using B. stearothermophilus as a reference organism (D121 = 0.5 min), and an initial bioburden of 100 spores, determine the sterilization time required to achieve a 1 in 100,000 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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