EMULSION. DEFINITION. Combine two immiscible liquid phases one of which is dispersed as globules (the dispersed phase) in the other liquid phase (the continuous phase) stabilized by presence of emulsifying agent . Pharmaceutical applications of emulsions.
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1. They can mask the bitter taste and odor of drugs,
e.g. castor oil, cod-liver oil etc.
2. They can be used to prolong the release of the drug
thereby providing sustained release action.
3. Essential nutrients like carbohydrates, fats and
vitamins can all be emulsified and can be administered to bed ridden patients as sterile intravenous emulsions.
4. Emulsions provide protection to drugs which are
susceptible to oxidation or hydrolysis.
6. Emulsions are used widely to formulate externally
used products like lotions, creams, liniments etc.
Based on type:
1- Oil in water emulsions (O/W)
2- Water in oil emulsions (w/O)
3- Multiple emulsions (O/W/O) or (W/O/W)
Based on size of dispherse phase:
2. microemulsion (nanoemulsion)
1. It should be able to reduce the interfacial tension between the two immiscible liquids.
2. It should be physically and chemically stable , inert and compatible with the other ingredients of the formulation.
3. It should be non irritant and non toxic in the conc., used.
4. It should be able to produce and maintain the required viscosity of the preparation.
5. It should be able to form a coherent film around the globules of the dispersed phase and should prevent the coalescence of the droplet of the dispersed phase.
acacia - tragacanth- pectin- starch,
derivative of cellulose (semisintetic)
gelatin- cholesterol – lecitin, wool fat
They show considerable batch to batch variation
readily support M.O. growth
A- Anionic emulsifying agents
Soap of di/trivalent metal
Amine soaps: N(CH2CH2OH)3
Sulfated and sulfonated compound
B- Cationic surfactants
C- Nonionic surfactants
E.g. Tweens (polyethylene fatty acid ester)
Span ( sorbitanfatty acid ester)
glycerylmonostearate, propylene glycol monostearate, macrogol esters such as polyoxylstearates and polyoxyl-castor oil derivatives
D- Amphoteric surfactants
low pH cationic
high pH anionic
1. Physical nature of the interfacial surfactant film
For Mechanical stability, surfactant films are characterized by strong lateral intermolecular forces and high elasticity (Analogous to stable foam bubbles)
2. Electrical or steric barrier
Significant only in O/W emulsions.
In case of non-ionic emulsifying agents, charge may arise due to
(i) adsorption of ions from the aqueous phase or
(ii) contact charging (phase with higher dielectric constant is charged positively)
No correlation between droplet charge and emulsion stability in W/O emulsions
3. Viscosity of the continuous phase
4. Size distribution of droplets
5. Phase volume ratio
As volume of dispersed phase stability of emulsion
(eventually phase inversion can occur)
Temperature , usually emulsion stability
Temp affects – Interfacial tension, solubility of surfactant, viscosity of liquid, phases of interfacial film
1. Dilution test
2. Conductivity Test
3. Dye-Solubility Test
4. Fluorescence test
1. Continental or dry gum method
Emulsifier is triturated with the oil in perfectly dry porcelain mortar
water is added at once triturate immediately, rapidly and continuously (until get a clicking sound and thick white cream is formed, this is primary emulsion)
the remaining quantity of water is slowly added to form the final emulsion
2. English or Wet Gum Method
triturate gum with water in a mortar to form a mucilage
oil is added slowly in portions the mixture is triturated
after adding all of the oil, thoroughly mixed for several minute to form the primary emulsion
Once the primary emulsion has been formed remaining quantity of water is added to make the final emulsion
3. Bottle or Forbes Bottle Method
It is extemporaneous preparation for volatile oils or oil with low viscosity.
gum + oil (dry bottle)
water (volume equal to oil) is added in portions with vigorous shaking to form primary emulsion
remaining quantity of water is added to make the final emulsion
a) Flocculation and creaming
b) coalescence and breaking/cracking
c) Phase inversion
d) Miscellaneous physical and chemical change
It may be brought about by:
e.g. anionic + cationic emulsifying agent
2- chemical or microbial decomposition of emulsifying agent
1. Determination of particle size and particle count
2. Determination of viscosity
3. Determination of phase separation:
4. Determination of electrophoreticproperties