What are the local uses?
Inflammation, pain, itching, protection, lubricant, emollient
What are the types of semi solids?
Ointments, creams, pastes, gels
What is the systemic action?
Percutol ointment (vasodilator)
What are the features of ointments?
- They are greasy
- have an oily (usually anhydrous) vehicle
- may contain a surfactant if used as a wash
- they are highly occlusive and so good for dry skin
What are the features of creams?
- they are semi solid emulsions
- they have a cooling effect on the skin
- less greasy and less occlusive than ointments
- they are hydrous so require preservatives
What are the features of pastes?
- stiff preparations so less spreadable
- they are ointments with up to 50% water
- they provide precise localised treatment
- forms a thick, impermeable layer on the skin
- they are used for lesions, sun block, rashes
What are the features of gels?
- they have two components, a polymer to produce a matrix, and a high water content
- they are used for lubrication or for mouth ulcers
What are the types of excipients needed in semi solids?.
oily/water miscible vehicles, gelling agents, surfactants, humectants, solids, preservatives, anti-oxidants
What are the different types of oily vehicles used?
- mineral oils such as liquid paraffin (these are occlusive but have limited penetration)
- Vegetable oils such as caster/olive/coconut (these can turn rancid)
- synthetic oils such as dimethacone (water repellent and occlusive)
What surfactant would be used for a w/o emulsion?
lanolin or bees wax
What do antioxidants do?
they prevent decomposition
In what ways can the stability of semi solids be affected?
They are affected by heat, light and microbial growth. Emulsions can crack
Oils can turn rancid
The higher the water content, the less stable
How can semi solids be packaged?
glass/plastic jars, aluminium/plastic tubes, pump dispensers, nozzles, sachets
What are the advantages of ointments and pastes?
- more stable than creams and gels
- occlusive and protective
- good for dry skin
- less need for preservatives
- some ointments can be used as washes
What are the disadvantages of ointments and pastes?
- they’re greasy and sticky
- slow skin absorption
- can’t be used on macerated skin
- high oil content can be flammable
What are the advantages of creams and gels?
- non greasy and more acceptable to patients
- rapid skin absorption
- have a cooling effect on evaporation
- can be used on macerated skin
- gels have less additives
What are the disadvantages of creams and gels?
- susceptible to microbial contamination
- require preservatives
- less stable and creams can crack (have a short expiry)
- short duration of action due to rapid absorption
Discuss aerosols for topical application
- They can be in solution or suspension formulated as liquid or foam
- They require a propellant such as CFC’s or HFA’s
- They’re packaged in metal canisters which can’t be stored above 50 degrees (chance of explosion)
- You have to shake the aerosol to disperse the propellant and drug
