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15 Cards in this Set

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What is an emulsion?
A course dispersion in which the dispersed phase is composed of small globules distributed throughout a vehicle that it is immiscible in.
Names the 3 phases of an emulsion.
Dispersed phase - internal

Dispersion medium - external phase or continuous phase

Emulsifying agent - third component to stabilize emulsion could be oil or water
Oils used in emulsions
Active ingredients: castor oil, liquid paraffin, cod liver oil

IV feeding: cotton seed, soya bean, safflower oil

For external: benzyl alcohol
Classification of phases
Oil in water
water in oil

less stable (control release systems)
o/w/o & w/o/w
Purpose of preparing emulsions.
To prepare stable and homogenous mixtures of immiscible substances

To optimize drug release and absorption by reducing droplet size (minute globules)
Emulsions as dosage forms.
Orally: o/w mask taste
IV: o/w only!
IM: w/o for extended release
Externally: either
Emulsions used externally depends on...
1. nature of the therapeutic agent

2.skin irritating agents (better in internal phase)

3. desirability of emollient or softening affect

4. condition of the skin surface
Advantages of w/o emulsions used externally.
Can be applied more evenly because skin has oil (sebum) layer.

More softening to the skin, resists drying out.
General requirements of emulsifiers as an excipient.
1. Most be compatible with other ingrediants

2. does not interfere with stability or efficacy of therapeutic agent

3. nontoxic

4. Little odor, taste, color
Types of Emulsifying agents:

Surfactants
Selection based on HLB:
(HLB 3-6) w/o
(HLB 8-18) o/w
Ionic properties of surfactants
Anionic and cationic not compatible

Nonionic effective over pH 3-10

Cationic effective over pH 3-7

Anionic effective over pH 8
Types of Emulsifying agents:

Hydropilic colloids
Type 1: Carbohydrate materials
Polysaccharides

Produce o/w emulsions

Mechanism:
interfacial film
Retard droplet settling (viscocity regulator - thickening agent)

Examples:
Acacia
Tragacanth agar
chondrus
Pectin
Microcrystalline cellulose
Types of Emulsifying agents:

Hydrophilic colloids
Type 2: Protein Substances
o/w emulsion

examples:
Gelatin
Egg Yolk
Casein
Types of Emulsifying agents:

Hydrophilic colloids
Type 3: High Molecular weight alcohols
Can be...
surfactants
Thickening agents
stabilizers

For external o/w emulsions for lotions and ointments use
stearyl alcohol, cetyl alcohol, or arid glyceryl monostearate

For external w/o emulsions use cholesterol and cholesterol derivatives
Types of Emulsifying agents:

Finely devided particles
Colloidal clays
Form o/w emulsion when:
1. aqueous phase is greater than oil phase
2. powdered solid is added to aqueous phase

Form w/o emulsions when:
1. when oleaginous phase is greater then aqueous
2. when powder solid is added to oil

Examples:
Bentonite
Magnesium hydroxide
aluminum hydroxide