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What is sterility?
Sterility is the total absence of pathogens in a finished sterile product.
Sterile products include: parenterals (injectables), ophthalmics, inhalation aerosols, and their administration devices.
One of the first steps in manufacturing a sterile product is the use of rigid aseptic procedures in a well designed controlled clean room environment.
Clean rooms are constructed, and maintained to prevent environmental contamination during manufacture.
- Includes:
- smooth walls and floors
- nonporous (e.g., stainless steel) counters
- Clean air – mostimportant component of the clean room
- Ultraviolet lights can also be used
How is clean air generated and maintained?
HEPA (High Efficiency Particulate Air) Filters: Used to filter the air that enters the clean room
- Removes 99.97% of particles 0.3 microns or larger
- Considerably reduces, but does not eliminate the chances of contamination
Positive Pressure: Filtered air admitted to a sterile area must be of higher pressure than the surrounding areas. This serves to force particles away from the clean room that might be introduced from other incoming areas, such as entry doors, or pass throughs.
Sterilization methods
sterilization = complete destruction or removal of living organisms and their spores
Physical Methods of Sterilization
Methods |
Conditions |
Applications/Comments |
1. Thermal
Moist (steam) heat |
121ºC for at least 15 min.
Conducted at high pressure in an autoclave. |
Economical, fairly low temperatures
Suitable for solutions, glassware, surgical
dressings, and instruments
Not suitable for oils, fats, or powders |
Dry heat |
170ºC for more than 120 min. |
For substances not effectively sterilized
by moist heat |
2. Filtration |
Retention of particles larger than the rated pore size
(generally 0.22 μm)
|
Only useful for solutions
Can be used for heat-sensitive products
Removes living and dead organisms and particulates.
Conven ient
Possible drug adsorption to the filter material |
3. Radiation |
Gamma-rays |
Can sterilize contents in sealed packages without heat. |
UV light (253.7 nm) |
Does not penetrate packaging well
Used most often as a step in maintaining sterile water systems |
Chemical Methods
4. Gas |
Diluted ethylene or propylene oxide |
Great penetration through packaging materials
Difficult, time-consuming, & dangerous |
Techniques for producing sterile solids
- Usually manufactured using sterile (aseptic) crystallization or lyophilization (freeze drying)
USP Sterility Tests
Sterility tests must be performed on all sterile products. The focus of these tests is on the absence of bacteria.
Two official (USP) methods: USP <71>
- Membrane Filtration (preferred)
- Direct transfer of sample to sterile culture media (used for all devices)
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