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15 Cards in this Set
- Front
- Back
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What is an emulsion?
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A course dispersion in which the dispersed phase is composed of small globules distributed throughout a vehicle that it is immiscible in.
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Names the 3 phases of an emulsion.
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Dispersed phase - internal
Dispersion medium - external phase or continuous phase Emulsifying agent - third component to stabilize emulsion could be oil or water |
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Oils used in emulsions
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Active ingredients: castor oil, liquid paraffin, cod liver oil
IV feeding: cotton seed, soya bean, safflower oil For external: benzyl alcohol |
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Classification of phases
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Oil in water
water in oil less stable (control release systems) o/w/o & w/o/w |
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Purpose of preparing emulsions.
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To prepare stable and homogenous mixtures of immiscible substances
To optimize drug release and absorption by reducing droplet size (minute globules) |
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Emulsions as dosage forms.
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Orally: o/w mask taste
IV: o/w only! IM: w/o for extended release Externally: either |
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Emulsions used externally depends on...
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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 |
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Advantages of w/o emulsions used externally.
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Can be applied more evenly because skin has oil (sebum) layer.
More softening to the skin, resists drying out. |
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General requirements of emulsifiers as an excipient.
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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 |
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Types of Emulsifying agents:
Surfactants |
Selection based on HLB:
(HLB 3-6) w/o (HLB 8-18) o/w |
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Ionic properties of surfactants
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Anionic and cationic not compatible
Nonionic effective over pH 3-10 Cationic effective over pH 3-7 Anionic effective over pH 8 |
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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 |
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Types of Emulsifying agents:
Hydrophilic colloids Type 2: Protein Substances |
o/w emulsion
examples: Gelatin Egg Yolk Casein |
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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 |
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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 |
