L5: Creams/ Ointments/ Pastes Flashcards
What is a cream always miscible with?
It’s continuous phase
What is a cream?
Two phase semisolid emulsion.
What type of cream is an ‘oily cream’ and what is its continuos phase?
Continuous phase = oil.
–> w/o cream.
What can oily creams be used as?
Bases.
–> and have good emollient properties.
Describe oily creams.
They are:
Creamy
White or translucent
Rather stiff
What type of cream is an ‘aqueous cream’ and what is its continuos phase?
Oil in water.
Continuous phase = water.
What can aqueous creams be used as?
As a base for RAPID ABSORPTION, and penetration of drugs.
Why are creams more acceptable than ointments? (4)
1) Less greasy
2) Easier to spread
3) Easier to wash away
4) Water evaporating from w/o cream has cooling and soothing effect.
How are drugs incorporated into a cream?
Soluble solids
Added into the molten base, at the LOWEST possible temperature, and stirred until cold.
How are drugs incorporated into a cream?
Insoluble solids
Incorporated using a tile and spatula.
More than one –> doubling up technique.
How are drugs incorporated into a cream?
Non volatile miscible liquids
Mixed with the molten base in an evaporating basin.
How are drugs incorporated into a cream?
Volatile or immiscible liquid
Triturate with the base in ointment tile.
Small amount of liquid can be folded into the base.
What type of surfactant can be used for o/w creams?
Ionic AND non ionic
What type of surfactant can be used for w/o creams?
Non ionic
What are ointments?
Semisolid preparations with greasy bases.
Ointment bases consist of a mixture of….. (3)
Waxes
Fats
Oils
What are 4 types of ointment bases?
1) Hydrocarbon bases
2) Absorption bases
3) Water-miscible/emulsifying bases
4) Hydrophilic (water soluble) bases
Describe hydrocarbon bases (3)
Water free mainly
Not absorbed by the skin
Usually consist of soft paraffin/ mixture of soft and liquid paraffin.
Hydrocarbon bases are used mainly for their emollient effect… Describe how?
Form a greasy waterproof film on the skin,
to prevent water loss from skin,
and therefore improve hydration of the skin.
Describe absorption bases?
Already w/o emulsion that permits the incorporation of small, additional quantities of aqueous solution.
Describe water-miscible emulsifying bases
Anhydrous bases,
Containing o/w emulsifying agents,
Making them miscible with water.
Describe hydrophilic bases
Contain both water soluble and insoluble components.
Incompatible with many chemicals, e.g. Phenol, iodine,potassium iodide.
Reduce anti microbial properties of quaternary ammonium compounds
Name advantages of hydrophilic bases (3)
Non irritant to skin
Easily washed off
Allows medications to mix with skin secretions
General considerations of selecting a base (5)
1) desired release rate of particular drug from ointment base
2) enhancing drug absorption
3) short/long term stability of the drug in base
4) influence of the drug on the features of the base
5) patient factors
How are semisolid products packed?
Always packed in jars or in tubes
Factors needed to consider during packaging and storage (5)
1) air
2) light
3) moisture
4) heat
5) possible chemical reactions between preparation and the container
What are pastes?
Semisolid preparations for external use.
Very stiff.
