Topical preparations e.g cream, ointment

What is the definition of topical + give examples

Something that is applied to any external body surface for a localized effect 

Eye, nasal mucosa, mouth buccal mucosa, rectal mucosa, vaginal mucosa, skin, skalp

What must be on all products for the skin

For external use only 

Why do we give treatment locally to the skin?

• To enhance barrier function of the skin

• Targeted delivery to specific layers of the skin e.g fungal infections on the outermost part of the skin but eczema needs to deliver drugs deeper into the skin 

• Fewer side-effects compared with oral delivery of drugs as it goes straight to its target 

What is the function of sunscreen ( topical lecture)

Protect against UV radiation 

What is the function of topical antibiotics for abrasions 

To protect against infection

What is the function of emollients ( preparations that add moisture)

Improve dry skin conditions, adds moisture 

What is the function of barrier creams

Prevent exposure of skin to harsh chemicals ( e.g for hair stylists)

What does occlusive mean 

The formulation prevents water movement out of the body, increases skin hydration and moisture content by locking in the water present 

Enhances skin barrier and forms a “shield” on skin 

Good penetration of drugs through the skin 

What type of skin is occlusive formulations good for and what is it bad for 

Good for dry skin 

Bad for infected skin, creates an environment for bacteria to grow

What are ointments 

Semisolid preparations intended for external application to the skin or mucous membranes ( e.g  nose, ear)

What are the two types of ointments composed of  for the skin

• Hydrocarbons from petroleum or other oils which are not water soluble 

• Emulsifying ( water-soluble/ washable ointments)

What is the main/ most common ingredient in ointments

Soft paraffin 

What is the role of liquid paraffin or hard paraffin

to thin or thicken formulations as needed

What are the two types of soft paraffin 

• Yellow petrolatum ( Petroleum Jelly) Vaseline

• White petrolatum ( white petroleum jelly) which has been bleached to remove yellow colour for people who are allergic

What are the properties of hydrocarbon ointments 

• Occlusive : prevents water movement out of the body

• Emollient :  softening or soothing the skin

• Skin hydration keeps skin supple

• Difficult to remove, just water doesn’t work 

• Greasy 

• Good if drug isn’t stable in water

EXAM QUESTION: If a drug is unstable in water + poorly water soluble, What formulation should be used

Ointment or suspension

What are the properties of water-soluble ointments 

• Water soluble 

• Washable 

• Non-greasy 

• Non-occlusive or not as occlusive as hydrocarbon ointments so they do not lock water in as well as hydrocarbon ointments 

What is a paste 

An ointment where we add high amounts of dry powder material, 20 to 50% of solid material 

Which is stiffer + thicker  ointments or pastes 

Pastes

Paste properties 

• Very good protective barrier - water impermeable 

• Prevent dehydration: used to prevent windburn on skiers 

• Pastes are used to prevent nappy rash - absorb ammonia from break down of urine

What are the two phases in creams 

Oil phase and a water phase 

What type of formulation are creams and what is needed to make them stable 

Creams are emulsions; they can be o/w (most common) or w/o

They need emulsifying agents ( surfactants) to stabilise them 

As well as an emulsifying agent, what else needs to be added to creams 

Preservative to stop contamination as water is present in creams 

What are the advantages (3) and disadvantage (1) of creams

• Good delivery system for many drugs 

• Good patient acceptability 

• Spread easily 

• Not as occlusive as ointments 

• For O/W creams, water evaporates to leave a thin “film” on the skin