Emulsion may be defined in a number of ways, but essentially, they are “heterogeneous system, usually containing two immiscible liquids”.

Purposes of emulsions
  1. Increased drug solubility
  2. Increased drug stability
  3. Prolonged drug action
  4. Improved taste
  5. Improved appearance
Types of Emulsions
  • Oil in water (o/w) emulsions is that type wherein oil droplets are dispersed in water.
    — This type of an emulsion is used for the administration of fats and oils, orally and parenterally,
  • Water in oil (w/o) emulsions — is that type wherein water droplets are dispersed in oil.
    — This type of an emulsion is used to disperse antigenic materials in mineral oil, for IM injection.
General Considerations of Emulsification
  • First Consideration: Knowledge of the various processes involved in emulsification to approach the formulation with some degree of confidence.
    • Droplet formation, formation of interfacial barrier, tendency of the particles to aggregate or coalesce
  • Second Consideration: Influence in viscosity
    — Emulsification process
    — Types of emulsion formed
  • Third Consideration: Emulsion Stability
    — Coalescence of droplets
    — Flocculation
    — Creaming
    — Sedimentation

Means of Detecting of Emulsion

  1. Dilution test
  2. Dye solubility
  3. Conductivity test
  4. Staining test (filter paper)
  5. Miscibility test
  6. Flourescence test
A. Dye solubility Test Amaranth green (-)
Sudan red (+)
B. UV Flourescence Test (+) absorption (-)
C. Conductivity (-) (+)
D. Cobalt Chloride Test Blue Pink
E. Direction of Creaming Sedimentation Creaming

Methods of Preparation

Dry gum (o + e) + w

Addition of gum to oil (mixing lightly to disperse), followed by adding all water and stir continuously & vigorously. Continuous trituration for further 2-3 minutes to produce white stable emulsion.

— The whiter the product, the smaller the globules. Other ingredients should be added gradually up to its final volume.

Wet gum (w + e) + o

Water is added to the gum and quickly triturated until gum has dissolved, to make mucilage. Oil is then added to mucilage in small proportions, triturating after each addition, until a thick primary emulsion is obtained.