Ben Forbes Flashcards
What is a pyrogen?
Fever inducing substance including microorganisms
Can be endogenous or exogenous
Example - LPS in gram -ve bacteria (endotoxin)
Where are pyrogens found?
Solvents
Excipients
Manufacturing apparatus
Mostly found in infusions due to large, moist environment ideal for growth
Why are heating, filtration and chemical disinfection unsuitable for eliminating pyrogen contamination of water?
- Chemical disinfectants can be toxic
- Thermostable so won’t be destroyed by heating
- Water soluble so you cannot filter it
- Insensitive to pH changes
How would you generate a pyrogen free water?
Distill sample at 80 degrees
What are the two pyrogen tests?
Done for all injections > 15mL and powders for reconstitution
- Rabbit test:
- Inject rabbit with sample and see if there is an increase in temp
- If 3 rabbits have combined increase of more than 2.65 degrees, the product fails
- Expensive, time consuming and ethical issues
- Some injections cause same response e.g.) insulin - LAL test:
- In vitro test for bacterial endotoxin based on clotting mechanism (amoebocytes) of horseshoe crab
- Crab has blue blood based from copper
- Enzymes from the crab’s blood + endotoxin will form a gel (coagulation). So if the blood clots, the sample contains an endotoxin
- This is a way to protect the crab
What are particulates?
Presence of visible/subvisible extraneous matter
Not part of the product itself
What formulation has the highest risk for particulate matter?
Large volume parenteral fluids
> 15 mL has to be IV, cannot be subcut or IM
Why can you not use sterilisation to kill particles?
They are not living
You can only use filtration
Where can particulates come from?
- Material may not be filtered out at the manufacturing stage prior to filling
- Material may not be removing during rinsing prior to filling
- Material may fall into final container from the environment (skin, hair, fibres, cellulose)
- Deposition of closure compartments during sterilisation such as clay
- Reaction or formulation with container (glaking of glass)
- Rubber fragments due to coring by needles
- Glass fragments when opening ampoules
Can use special glass that is non-shedding
What are the risks associated with particulate matter?
- Vacular occlusion - could block artioles and capillaries forming emboli. This is particularly the case with the capillaries in the lung as they are very thin and can result in scarring on their lungs e.g. IV drug users
- Inflammatory response - irritation around where the particle has lodged
- Neoplastic response - potential for cancer if over a long period of time
- Antigenic response- patient becomes more sensitised to material which can cause an allergic response
In terms of particulates, what does the risk depend on?
- Size of particle
>8 micrometers will lodge in lung
3-5 micrometers will be taken up in liver and spleen - Size of blockage
- Nature of particle
- Risk increases with increased number of particles
- Shape and surface characteristics as this can affect adherence and where it will get lodged
- Host response from the body
What are the 4 main ways to detect particles?
- Visual inspection
- Optical microscopy
- Electrical sensing zone method (Coulter counter)
- Light blockage method
What is visual inspection?
What are the advantages and disadvantages?
Can see particles 50 microns from naked eye
GMP recommends that you examine each container by trained personnel
Advantages:
- Detects gross contamination and incompatibilities with mixture
- Non destructive
Disadvantages:
- Subjective
- Only larger particles are detected
- Needs to be in a clear plastic container
What is optical microscopy?
What are the advantages and disadvantages?
USP METHOD
25mL solution is filtered and particles are collected on the filter membrane and counted
Advantages:
- Identification of particles
Disadvantages:
- Labour intensive
- Special facilities needed
- Difficult with oily and viscous solutions
- Only a small sample is measured
What is electrical sensing zone method?
Based on Ohm’s law V=IR via a conducting system
Measures resistance of particle in fluid blocking the orifice and measures its equivalent spherical diameter (volume)
Counts and sizes particles
Advantages:
- Not dependent on operator technique
- Reliable, reproducible
Disadvantages:
- Bubbles - false counts
- 2 particles are counted as one
- Destructive so only tests a small number of samples
- No identification of particle
