Emulsion

• Emulsions are heterogeneous systems consisting of at least one immiscible liquid that is intimately dispersed in another liquid in the form of droplets or globules
• Emulsions are thermodynamically unstable mixtures of two essentially immiscible liquids with an emulsifying agent to hold them together
• The process of combining immiscible liquids with an emulsifying agent is termed as emulsification
• Components of an emulsion:

  • Dispersed phase (internal phase or discontinuous phase)
  • Dispersion medium (external phase or continuous phase)
  • Emulsifying agent
• Emulsions are used as a dosage form when two immiscible liquids must be dispensed in the same preparation
• O/W Emulsion:

  • Dispersed phase: non-polar (oil)
  • Dispersion medium: polar (water)
  • Characteristics: miscible with water, water washable, can absorb water, non-occlusive, and non-greasy
• Forms of emulsions:

  • Topical creams and lotions
  • Drugs in liquid forms
• Methods of Preparation:

  • English method/wet gum: relies on the use of mucilages or dissolved gums, involves adding oil in small quantities by using rapid trituration, and then slowly adding more water until complete
  • Continental method/dry gum (4:2:1): involves rapid mixing of the hydrocolloid with the oil, then adding water all at once with rapid trituration until the emulsion is complete