Formulation of Advanced or Complex Medicines 7 Flashcards
Why is extensive desorption needed with ethylene oxide?
Diffuses readily into many packaging materials
- rubber
- plastics
- fabric
- paper
What are the limits of ethylene oxide on plastic syringes?
10 ppm
How can the chance of explosions with ethylene oxide be reduced?
Explosive in as little as 3% air
Use restricted to tightly sealed, enclosed environment
What is the process of gaseous sterilisation using ethylene oxide?
Air can limit ethylene oxide penetration
- draw a vacuum
Low pressure also allows production of low temperature steam
- control humidity (40 - 80%)
- control temperature (45 - 65C)
Ethylene oxide is injected
Forced gas circulation is often employed to minimize variations in conditions throughout the steriliser chamber
What concentration of ethylene oxide is used for gaseous sterilisation?
400 - 1200 mg/L
How is ethylene oxide evacuated from the chamber after gaseous sterilisation?
Gases are evacuated either directly to the outside atmosphere or through a special (catalytic) exhaust system
Desorption of ethylene oxide from chamber/load by a series of vacuum and steam pulses, followed by vacuum and pulses of sterile air to cool and dry the load
How long does ethylene oxide sterilisation take?
Slow processes - even at high temperatures
22 mg/L = > 24 hours
44 mg/L = 24 hours
88 mg/L = 10 hours
442 mg/L = 4 hours
884 mg/L = 2 hours
As concentration increases, aeration time
What are the advantages of using ethylene oxide for gaseous sterilisation?
High penetrability
Sterilisation of temperature sensitive materials
Not degrading to plastic/metals etc
Rapidly degraded in the environment
What are the disadvantages of using ethylene oxide for gaseous sterilisation?
Toxicity
Flammability
Long cycle times
Cannot be used to sterilise liquids
What materials can be sterilised by radiation?
Liquids
- disinfectants
- water
- serum
- proteins
- enzymes
Foods
- fruits and vegetables
- meats
- pre-packaged meals
Devices
- pacemakers
- implants
- needles
- syringes
Other materials
- plasticware
- gloves and gowns
- bandages
What types of radiation can be used for sterilisation?
Gamma rays
Accelerated electrons
- beta rays
UV light
- limited application
- surface sterilisation
- water
Infrared radiation
- limited application
- surface sterilisation
- dry heat sterilisation
What are the advantages of radiation sterilisation?
‘Cold’ proecss
- no preconditioning for heat/humidity
No aeration phase required to make products residue/chemical free
What is the mechanism of action for ionising radiation in radiation sterilisation?
Strips off electrons from the atoms of the material through which it passes
- energy from this radiation results in ionisation
- highly active electrons
- highly reactive free radicals
What does radiolysis of water lead to?
Breakdown into assorted chemicals, electrons and free radicals
What are free radicals responsible for?
Structural damage in microbial DNA
- OH radicals will cleave phosphodiester bonds in DNA
Unless repaired will inhibit DNA synthesis or cause errors in protein synthesis
