Practical Flashcards
Potable water meaning
Tap water - taken from mains supply and suitable for drinking
What is potable water suitable for?
Internal and external preparations
What is potable water not suitable for?
- injectable preparations
- ophthalmic preparations (for eyes)
What is purified water?
Distilled potable water
When would purified water be used instead of potable?
- when mains water comes from storage tank
- if mains water unsuitable for formulation
What is purified water used for?
Internal and external preparations including ophthalmic preps
Which kind of water is PREFERRED for external preparations?
Purified
For what reasons might the means water be unsuitable for a preparation?
- water contains high levels of dissolved or undissolved solids
- water has high or low pH
What must be done with purified water before use?
Freshly boiled and cooled
Why must purified water be boiled and cooled before use?
Likely to be contaminated with microorganisms
What sort of water must be used for injectable medicines?
Water for injections BP
When preparing a liquid formulation, what must be the first step?
Establish the solubility of the ingredients in the diluent(s)
For what two reasons is it necessary to make a small extra amount of product?
- as an ‘excess’ to allow for losses in production
- as an ‘overage’ i.e. to ensure the entire dose can be withdraw from a single-dose container and administered to the patient
For sorts of formulation would an ‘excess’ be necessary?
What percent more more product is recommended?
Creams, ointments, suppositories
30-50%
For what sort of formulations would an ‘overage’ be necessary?
What % more product is recommended?
Injections
10%
Why are preservatives included in formulations?
- to protect against microbial growth
- to extend shelf lives
Why is it better not to include preservatives in oral medicines for children?
Preservatives have been known to cause adverse effects
What does BP stand for?
British Pharmacopoeia
When was chloroform removed from the BP?
2016
What are preservative-free products at a greater risk for?
Microbial growth
How can the risk of microbial growth in preservative-free products be reduced?
- single-use containers
- sterilisation
- shorter shelf lives
- refrigerated storage
A product designated by the BP as being ‘freshly prepared’ is usually prepared assigned how long of a shelf life?
14 days
A product designated by the BP as being ‘recently prepared’ is assigned how long of a shelf life?
28 days
A product’s expiry date cannot be later than the what?
The expiry date of the ingredients
How do you decide an appropriate expiry date for a product if no shelf life is available from a monograph?
Base it on the products’ stability and risk of microbial contamination
What is the most common shelf life given to extemporaneously produced solutions, suspensions and emulsions?
14 days or 7 if preservative-free
Products containing what can be classed as ‘self-sterilising’?
- > 15% alcohol
- > 85% syrup
- high conc of sugar plus polyol
How o you assign an expiry to a self-sterilising product?
As if a preservative is present
What is the common shelf life of semi-solids e.g. ointments and creams?
7-14 days
What is the common shelf life of solids e.g. suppositories?
28 days if no water present
What is the BP?
Reference source for the quality control of medicines in the UK
What two pharmacopoeia’s have legal status in the UK?
- British
- European (PhEur)
What is Martindale: The Complete Drug Reference used for?
Detailed info on nomenclature, physical and pharmaceutical properties, adverse effects, use of drugs, etc etc
What is Article 65?
Lists all excipients that could have an effect on the patient
(Must always be listed on a medicine’s label if present or at above listed ‘threshold’ concentration)
What are the electronic balances capable of weighing in the lab?
Between 100mg and 200g
What are the electronic balances capable of weighing in the lab?
Between 100mg and 200g
If a quantity of less than 100mg is required what is needed?
A dilution or titration
What are the required characteristics to measure out a weight of excipient of less than 100mg?
- minimum of 100mg
- multiple of 10
If we need 30mg of an excipient, how much might you weigh out?
120mg because
- over 100g
- multiple of 30
How do you decide how much diluent to use?
Consider
- The multiplication factor e.g. for 30mg it was 30mg x 4 for 120mg so try to use a volume divisible by 4
- The volume available in the final product
E.g. working formula: drug to 30mg, syrup 25ml, water to 50ml (here the volume of drug-containing vehicle must be 25ml or less bc 50-25) - Solubility of drug (see martindale or BP)
(Easier to select volume of diluent that will allow drug to dissolve)
Why must a measure be clean and dry before measuring liquid?
Greasy measures will give a flattened, inaccurate meniscus
Why must a bottle of liquid be shaken?
To ensure we obtain a homogenous mixture
Solutions should not be made in a measure unless you are certain of what?
That the solid will dissolve in the available amount of solvent, as it may require heating and solute may be lost when transferring to suitable container
Many excipients have more than one use. what factors can help decide why an excipient has been included?
- type of product being made
- concentration of excipient
What is one advantage of using natural products in a formulation?
Usually cheaper than synthetic products
What are the disadvantages to using natural products in a formulation?
- Can suffer from batch-batch variation more than synthetics, semi-synthetics
- More of a risk for spore and/or microbial contamination
How can the risk of microbial contamination be accounted for when using natural products in formulations?
- use for short shelf-life products
- use antimicrobial preservative
What are some examples of polysaccharides used as viscosity modifiers?
- tragacanth
- alginates
- acacia gum
- starch
- xanthan gum (Keltrol)
What can polysaccharide viscosity modifiers be used to form?
- viscous, thixotropic, pseudoplastic preparations
- internal or external preparations (though sometimes too sticky for external)
What are some disadvantages to polysaccharides as viscosity modifiers?
- quite narrow pH stability ranges
- used mainly for short shelf-life products as usually natural
Why are acacia and starch often used in combo with tragacanth?
They do not give very viscous systems alone
What are some examples of water-soluble celluloses as viscosity modifiers?
- sodium carboxymethylcellulose
- methyl cellulose
- hydroxyethylcellulose
- microcrystalline cellulose
What are some characteristics of water-soluble celluloses as viscosity modifiers?
- semi-synthetic polysaccharides with varying chain lengths
LONGER chain lengths = INCREASED viscosity - stable over wide pH ranges
- some are non-ionic so suitable for use with ionic additives
What are some examples of hydrated silica’s ad viscosity modifiers?
- bentonite
- hectorite
- magnesium aluminium silicate AKA Veegum
What are some advantages to hydrated silicas as viscosity modifiers?
- natural products therefore relatively cheap
- can be used for internal and external meds
- readily absorb up to 12 times their own mass of water, forming thixotropic gels
What are two other commonly used viscosity modifiers?
- Carboxypolymethylene
- Colloidal silicon dioxide
What are some characteristics/considerations of carboxypolymethylene as a viscosity modifier?
- synthetic
- usually used externally
- forms very high viscosity product between pH 6 and 11 only
What are some characteristics/considerations of colloidal silicon dioxide as a viscosity modifier?
- aggregates in water to form a 3D product
- can be used in non-aqueous suspensions
What are some characteristics/considerations of colloidal silicon dioxide as a viscosity modifier?
- aggregates in water to form a 3D product
- can be used in non-aqueous suspensions
