Formulation of Advanced or Complex Medicines 8 Flashcards
What are high energy gamma rays used for in radiation sterilisation?
Industrial sterilisation of heat-sensitive products
Generally applied to articles in the dried state
- surgical instruments
- sutures
- prostheses
- unit-dose ointments
- plastic syringes
- dry pharmaceutical products
How is high energy gamma radiation sterilisation carried out?
Continuous-duty process
- products on a conveyer belt are passed through the rays/beam
What dose is used for sterilisation using gamma radiation?
Dose depends on exposure time
- typically 20 hours
What is the source of high energy gamma rays in radiation sterilisation?
Derived from isotopes
- cobalt-60
- caesium-137
Isotopes spontaneously decay from a high to a low energy state over time
Half life of 5.25 years
- Co-60 -> non-radioactive nickel
Radiation reduces by around 10% per year
Emits radiation at two energy levels
- 1.33 MeV
- 1.17 MeV
What are the advantages of high energy gamma rays in radiation sterilisation?
Mass processing
Highly effective
Products available to release immediately
What are the disadvantages of high energy gamma rays in radiation sterilisation?
Some product materials may be affected by the radiation
- effects greatest in presence of water
Destructive process may continue after sterilisation finished
Discolouration of some glasses and plastics
- PVC
Liberation of gases
- hydrogen chloride from PVC
Hardness and brittleness properties of metals may change
What are the two types of filtration used in filtration sterilisation?
Liquid filtration
Gas filtration
What is liquid filtration used for?
Generation of water for steam production
Critical applications
- water for injection
- rinsing water for medical devices
Temperature sensitive materials
- antibiotics
- vaccines
- ophthalmic solutions
What do the regulatory authorities state about filters used for liquid filtration?
The filter material must not shed fibres or leach undesirable material into solution being sterilised
What is gas filtration used for?
Air decontamination
- treatment of air supplied to aseptic areas
- clean rooms
- isolators
Part of venting systems on fermenters, centrifuges, autoclaves and freeze-dryers
Medicinal gas
- sterile
What is the most commonly used air filter?
High Efficiency Particulate Air (HEPA) filter
What size particles can HEPA filters remove?
HEPA filters can remove 99.997% of particles greater than 0.3 um in diameter
- removal efficiency is good since the majority of bacteria are found associated with the dust particles and only the larger fungal spores are found in the free state
- pre-filters are used to remove larger particles to extend the lifetime of the HEPA filter
What is screen/sieve membrane filtration?
Involves filtration across a membrane
All particles greater than a given size are excluded from the filtrate
- have an absolute pore size rating (e.g. 0.2 um)
Made from natural polymers
- cellulose acetate
- some plastics
- polyethersulfone
Can be sterilised by moist heat or ethylene oxide
What size filters are most commonly used in screen/sieve (membrane) filtration)?
0.2 - 0.22 um
- must be capable of retaining Pseudomonas (Brevundimonas) diminuta at a level of 10^7 cfu/cm^2 of filter
How can the efficiency of screen/sieve (membrane) filtration be increased?
Several discs can be used in parallel in multiple-plate filtration systems
Membrane filters can be fabricated into cylinders and installed in cartridges
Filters may be pleated
