semi solid preparation Flashcards
where do epidermal semi solids work?
locally at the skin’s surface
uses of epidermal semi solids:
antimicrobials, astringents, lubrication, moisturising, UV protection
where do endodermal semi solids work?
work locally in dermis or lower (Second layer under epidermal)
uses of an endodermal semi solid:
anti-inflammatory, local anaesthetic, anti itching
where do ttransdermal semi solids work?
absorb through the skin, but they work systemically (below all dermal layers)
uses of transdermal semi solids:
heart medicines, hormone replacement therapy. for transdermal delivery systems, patches are more common than demi solids
different types of semi-solid formulations?
creams, gels, ointments, pastes
what is more greasy, ointments or creams?
ointments due to their oily vehicle (liquid paraffin, soft paraffin, paraffin wax)
when may an ointment contain a surfactant?
when used as a wash
uses of ointments:
emollients, local and systemic drug delivery, eyes. highly occlusive therefore good for dry skin
how does a cream feel on the skin?
cool on the skin
why does a cream require a preservative?
its hydrous, high water content,
uses of a cream:
emollient (skin softening) and local drug delivery
what’s more occlusive, ointments or cream? what is the benefit for each
ointments are more occlusive so good for dry skin.
creams are less occlusive so good for macerated skin
what doe a paste feel like?
stiff
how does a paste relate to an ointment?
its an ointment with up to 50% powder
what are pastes used for:
lesions, skin protectants, sun block. it provides a v precise localised treatment.
how does a paste work?
it forms a thick impermeable layer on the skin
which semi solid is a 2 component semi solid?
gel
which semi solids have a high water content?
gels, creams
what are gels used for?
lubrication, delivering a drug (drug diffuses through the gel for delivery to site of action). use in the mouth (bongela)
List excipients found in semi solids
oily vehicles, water miscible vehicles, gelling agents, emulsifying agents (surfactants), humectants, solids, preservatives, anti-oxidants
list types of oily vehicles:
mineral oils, vegetable oils, synthetic oils. all are occlusive
what is liquid paraffin, soft paraffin, paraffin wax
oily vehicles
list some water water miscible vehicles:
water, alcohols and macrogols
what part does alcohol play in excipients?
it is a water miscibile vehicle. it is used for cooling via evaporation
list some aqueous gel gelling agents:
tragacanth, alginates, pectin, gelatine. they vary in viscosity.
what do emulsifying agents (surfactants) do?
- help oil and water to form a stable uniform mix.
- will also increase the penetration of the drug
list some emulsifying agents for water in oil:
lanolin, beeswax
what is beeswax?
an emulsifying agents used in water in oil semi solids
list some emulsifying agents (Surfactants):
polyethylene glycols, non ionic surfactants, emulsifying waxes
what do humectants do?
reduce water loss from creams and gels.
examples of humectants
glycerol, propylene glycol
examples of preservatives:
EDTA, parabens.
what is a disadvantage of using preservatives?
they can cause allergy / skin sensitisation
what affects the stability of semi solids?
heat, light, microorganism growth
what can happen to oils over time?
turn rancid
What composition must a semi solid have to be most stable?
products low in water are most stable (ointments and pastes)
which semi solids are the most stable?
ointment and pastes
Advantages of ointments and pastes:
they are more stable than creams and gels, they are occlusive and protective so good for dry skin, less need for preservatives, some ointments can be used as washes.
Disadvantages of ointments and pastes:
they are greasy and sticky so less appealing, they absorb slower into the kin, not to be used on macerated skin, high oil content so can be flammable
Advantages of creams and gels:
Non greasy so more accepted by patients, absorb rapidly into the skin, they have a cooling effect on evaporation, can be used on macerated skin, gels have less additives
disadvantages of creams and gels:
susceptible to microbial contamination so require preservative which could cause sensitiation, they are less stable and creams can crack (short expiry). short duration of action due to rapid absorption
why must you shake the aerosol?
to disperse the propellant and drug
give 3 examples of propellants
Hyroflouro-alkanes (HFAs) Vs Chloroflourocarbons (CFCs)
Butane
why do you need to grind and sieve powder?
to increase surface area and reduce clumping
what is trituration?
Method of incorporation of liquids or powders into a semi-solid base using a ceramic tile
Powders – doubling up and mixed using levigation
Liquids – making a small well and then mixed in gradually
what is levigation?
Applying pressure to incorporate a powder into a semisolid
Avoids a gritty product
what are some things that you need to check about the product during the final check?
uniformity, correct final weight, appearance, clean jar
