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Summary Sterilisation methods
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Industrial pharmacy - 1st semester Includes bullet points, key diagrams and images
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Sterilisation MethodsDefinitions
Sterility- absence of viable micro-organisms
Sterilisation- process to achieve sterility
Sterility assurance level (SAL)- probability that organisms survive (terminally
sterilised products <10-6 and aseptic<10-3 meaning 1 micro-organisms in 10-3
vials)
Sterilisation
Most preparations sterilised in final packaging
Injections and IVs
Sterile fluids
Implants
Dressings
Moist Heat Sterilisation
Using high temperature and pressure (steam)
Usually done in an autoclave
121oC/15psi for 15 minutes
Method of choice for thermostable aqueous preparations
Causes hydrolysis of proteins
Heating is effected by: size and shape of container, size of load and porosity and
entrapment of air
MHS for Bottled Fluids
Autoclave cycle
1. Air removed and steam administered (20-30 minute heat up)
2. Expose (holding phase)
3. Cooling (spray cooled)
MHS Porous Loads
Wrapped goods and porous materials
1. Air removal (vacuum)
2. Pulses of steam and evacuation in cycles (improve air extraction and steam
penetration)
3. Common conditions 134o for 3 minutes
4. Drying via steam exhaustion and vacuum
5. Restore air pressure and administer sterile air
6. Cycle 35 minutes
MHS Flexible/Semi Ridge Containers
Products in flexi bags like IVs
1. Air ballasting- proportion of air in chamber to prevent the package from
breaking (no vacuum) and fan to mix steam
2. Heating and holding period
3. Steam stopped by pressure maintained
, 4. Water/cooled air to cool- product not removed until safe temperature and
pressure is reached
5. Can be done at 121o for 15 minutes or as low as 115o for 30 minutes
Advantages
Terminal process for aqueous solutions
Wide safety margin
Kills bacteria and viruses
Disadvantages
Product must be thermostable
Cant be used for oil based products
Dry Heat Sterilisation
No steam so use higher temperature
160o for 2 hours, 170o for 1 hour or 180o for 30 minutes
Used for thermostable dry powders, oil based injections, glassware or metal
instruments
Heat oxidises proteins
Slower and less efficient than MHS
Used if paper, cardboard or aluminium
Avoid packing in many items
Screw cap containers half unscrewed to prevent bursting but tighten after
cooling
DHS Process
1. Load should all be same size and type
2. Pack the oven evenly spaced and containers are sealed or covered
3. Heat transferred by convection (fan) and radiation (reflect off oven)
4. Air cooling with HEPA filter
Advantages
Used for substances affected by moisture
Suitable for assembled apparatus
Less damage to glass and metal than (MHS)
Disadvantages
Damages plastic or rubber
Not suitable for dressings as doesn’t penetrate and causes deterioration
Gaseous Sterilisation
Ethylene oxide
Volatile at RTP
Miscible in water
Explosive in air so mixed with 10% CO2 or HFCs)
Toxic, irritant, burns and carcinogenic
Application of Ethylene Oxide
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