Preservatives Flashcards
what are the consequences of microbial contamination of pharmaceutical products
- spoilage/ aesthetic effects/product changes
- toxic effects/health hazards
give examples of spoilage, aesthetic effects and product changes that can occur
- visible evidence of growth such as fungal colonies, turbidity or colour changes
- organoleptic properties affected as a result of microbial growth or breakdown of product
- audible effects- gas production, fizzing, explosions
- degradation of active constituents/excipients
- most ingredients are susceptible to microbial attack
give examples of toxic effects and health hazards that can occur
- production of toxins
- gram - bacteria contain lipopolysaccharides in their outer cell membranes - infections in patients and end users
- contamination by pathogens can result in infection
- in hospitals, contamination of multi dose products can serve as vehicles for spread of disease
what are the impacts of microbial contamination to the pharmaceutical industry
- product recalls
- loss of sales
- financial loss
- decreased customer confidence
- damage to company’s reputation
- legal proceedings
what are sources of contamination of pharmaceutical products
- raw materials
- environmental contamination
- manufacturing sources
- while in use
what are the different raw materials used
- mains/raw water
- purified water
- water for injections
- excipients and actives
what should be noted when using mains/raw water
- should be free from faecal coliforms
- eg. E coli - other microorganisms may be present
how is purified water achieved and what should be noted
- distillation, reverse osmosis, ion exchange
- Pharmacopoeias specific total viable counts
- pseudomonas aeruginosa grow in purified water
what is water for injections and what should be noted
- purified water sterilised by autoclaving
- water used as an ingredient of sterile medicines is often stored at temperatures greater than 80
- to prevent bacteria multiplying and increasing endotoxin load
give examples of genera of typical water borne bacteria
pseudomonas, klebsiella
what should be noted with the use of excipients and actives as raw materials
- synthetic compounds generally have low bioburdens
- raw materials of natural origin are at a greater risk
what is involved in environmental contamination
air and personnel
explain how air is a source of environmental contamination
- not a natural environment for microbial growth
- but untreated air contains bacteria, moulds and yeasts
- air contamination depends on the activity in the environment and the amount of dust which is disturbed
- handling of contaminated materials during dispensing, blending and their addition to formulations
- some packaging components contain moulds and bacteria, reflected in high counts around packaging machines
give examples of bacteria commonly isolated from air samples
spore forming bacteria
- bacillus
staphylococcus
give examples of sources of human contamination
- skin scales
- saliva
- gut bacteria
give an example of a manufacturing source of contamination
equipment
- biofilm formation is problematic
what is meant by contamination while in use
during storage, in use by patient, consumer, nurse or doctor
which pharmaceutical products offer higher contamination risk while in use
multiple use medicines offers higher risk of contamination
define contamination
introduction of organisms into or onto the product
define spoilage
result of subsequent microbial proliferation
does contamination always lead to spoilage
no
which pharmaceutical products are vulnerable to spoilage
- products containing water
- available to participate in chemical reactions and in quantities for growth to occur - dry products such as tablets, capsules and powders are not very susceptible to microbial spoilage
what are the factors affecting risk of contamination and spoilage
- types and size of microbial inoculum
- nutritional factors, moisture content and water activity
- storage temperature and pH
- packaging design
- protection of microbes within a product
- mode of intended use
- how long is the product likely to be used/stored
what does a risk assessment for the preservation of pharmaceutical products involve
- strategies to limit contamination and spoilage designed to deal with worse case scenarios
- must assume that all microorganisms are infective for routes of administration where likelihood of infection from contamination is high
- where risk is perceived to be lower, less expensive but also less effective measures are used to limit contamination
what is the ultimate in use contamination control
to supply sterile, single dose, individually packaged applications
what are the strategies available for the preservation of pharmaceutical products
- low temperature storage
- pH manipulation
- water activity manipulation
- use of specific chemical preservatives
describe how low temperature storage can be used for the preservation of pharmaceutical products
- some medicines stored at low temperatures to prevent spoilage
- often used for short term storage of unpreserved or weakly preserved products
- not suitable for most products
Describe how pH manipulation can be used for the preservation of pharmaceutical products
- useful for foods and other domestic products
- less useful for pharmaceuticals
- microbial spoilage is rare above pH 8
- fungi spoilage is more likely between pH 3-4
describe how water activity manipulation can be used for the preservation of pharmaceutical products
- for spoilage to occur, microbes require water
- no growth is expected below Aw 0.5
- Aw is very low for tablets and other dry products
- lower Aw of some aqueous formulations in order to inhibit microbial attack
- may be achieved through addition of solutes such as sugar
what is water activity Aw
the parameter that describes the amount of free water in a solution
- has no units
- scale from 1 (pure water) to 0
what is the equation for calculating Aw
Aw= vapour pressure of solution/vapour pressure of pure water
give examples of limiting values of Aw for microbial growth
- moisture soption isotherm
- enzyme activity
- mold growth
- yeast
- bacteria
outline the limitations of Aw modulation for preservation
- difficult to predict changes in Aw during storage
- appropriate and more expensive packaging may be required to stabilise Aw over lifetime of the product
- many fungi can grow at an Aw of 0.65 and it is difficult to lower Aw of aqueous solutions to this level
describe how specific chemical preservatives can be used for the preservation of pharmaceutical products
- to deal with possible contamination during storage, limit growth of contaminants and prevent spoilage
- never should be added to deal with contamination or spoilage as a result of heavily contaminated raw materials or poor manufacturing process
what are the properties of an ideal preservative
- broad spectrum of antimicrobial activity and no vulnerability to resistance development
- gram + and gram - bacteria, yeasts and moulds - rapid antimicrobial action/rate of kill
- chemically stable, effective under all pH conditions
- compatible with excipients and packaging materials
- non volatile, odourless and tasteless
- good solubility in water
- low toxicity and cost effective
how is a preservative selected
- no single preservative satisfies all criteria
- selection is a compromise determined by formulation characteristics and intended use of the product
- range of preservatives greatest for topical drugs and more restricted for oral and parenteral products
