what are the 3 types of stabilities in medicines?
- chemical
- physical
- microbiological
what is degradation? what could it be a change in?
- any chance that adversely affects the properties of the medicine
could be a change in:
- chemical composition (eg. amount of drug)
- physical characteristics (eg. caking or suspension separating)
- performance of the medicine (eg. rate of drug release)
- microbial contamination
describe the pharmaceutical term: pack
- the container, wrapper, leaflets etc.
- the whole packaging, everything you require to give to the patient
describe the pharmaceutical term: container
- the first layer the medicine comes into contact with
- the barrier that provides the main protection to the formulation against the environmental factors that cause degradation
- eg. for Calpol, amber glass bottle
describe the pharmaceutical term: shelf life
- the time over which a medicine in a specified pack remains stable when stored under the recommended conditions
- it’s the whole medicine / pack combination that provides the stability
- over the whole shelf life the medicine must remain stable as long as in the correct conditions
describe the pharmaceutical term: expiry date
- the ‘use by’ date on label
- tells the user the shelf life
describe the pharmaceutical term: storage conditions
- conditions under which the medicine should be stored to achieve its shelf life
- expiry only applies if kept within the conditions
what is potency?
- the amount of drug remaining in the medicine after storing it
- in stability testing, usually expressed as a percentage of the original drug content (‘label claim’)
what is the label claim of a medicine?
what the manufacturer is claiming is in the medicine
what is considered a ‘stable’ medicine?
- 90% of label claim must be retained by the end of the shelf life (10% loss is allowed)
- reduces to 5 or 3% loss allowed if toxic products are produced
what are stability tests?
- provide scientific evidence for shelf life and storage conditions
- manufacturer undertakes stability tests to prove the product is stable for how long they’re stating it will be
what is the desired effect of a product/pack combination?
- designed to maximise stability
- 4 factors work together to maximise shelf life for as long as possible
what are the 4 factors within a product/pack combination that work together to maximise shelf life?
- pack design
- drug and medicine stability
- storage conditions
- medicine design (formulation)
state some physical mechanisms that can give rise to instability
absorption
diffusion / partition
evaporation
particle size changes
separation
solubility changes
state some chemical mechanisms that can give rise to instability
hydrolysis
photolysis
oxidation
enzymes from microbes
state some consequences of instability
- changes in the rate of drug release from a medicine
- dose uniformity problems (over or under dosing)
- changes in the colour, smell and texture
- changes you cannot detect easily
- microbial growth
explain how colour, smell and texture can change in medicines and what these mean
- usually indicate chemical degradation
- can be a sign of microbial growth
- loss of drug and excipients
- loss of palatability
- medicine can’t be used
consequences of microbial growth in injections
- blood infections
- growth up catheters into bloodstream
consequences of microbial growth in eye and nose drops
- transfer of infections
- are they being used on other family members?
consequences of microbial growth in oral medicines
- sickness and nausea
- food poisoning
- loss of drug and excipients
- nasty smells and taste
what are the dose uniformity problems in solutions?
- precipitation due to solubility limit
- eg. paracetamol syrups in the fridge
