O

• Emulsions

  Liquid preparation: oil and water (two immiscible liquid phases one dispersed in the other)
• Emulsions

  • Homogenous dispersion
• Surfactants

  Surface active agents
• Types of surfactants

  • Anionic
  • Cationic
  • Amphoteric
  • Non-ionic
  • Polymeric
• Anionic surfactants

  • Advantages: cost, low toxicity and biodegradable
  • Disadvantage: precipitation in Ca2+ and Mg3+ ions
• Cationic surfactants

  • The most common are quaternary ammonium compounds
  • Cationic materials are irritant to the skin
• Amphoteric surfactants

  • Contains both anionic and cationic groups
  • The main characteristic depends on the pH
• Non-ionic surfactants

  Mainly span and tweens
• Polymeric surfactants

  • They are excellent dispersing and stabilising power for hydrophobic particles in water
  • Highly concentrated suspension can be made
  • Polymeric surfactants modified for use as surfactant
• Surfactants are not pure
• Uses of surfactants

  • Wetting and spreading
  • Emulsification
  • Stabilising
  • Solubilising
• Emulsification

  • Most are non-ionic
  • This means less toxic/irritant and no pH effects
• Bancroft rule

  • Emulsification depends more on the nature of emulsifying agents
  • The phase in which an emulsifier is more soluble constitutes the continuous layer
• O/W emulsions

  • Oil is the internal and water is the external
  • High HLB surfactant
• Emulsion

  • Homogenous dispersion of two or more immiscible phases
  • Surfactants are the emulsifiers
• Types of emulsions

  • Oil in water
  • Water in oil
  • Multiple emulsions
• External phase

  Dispersion medium = continuous phase
• Internal phase

  Dispersed phase = discontinuous phase
• Milk is a natural emulsion
• Why emulsions?

  • Draggability
  • Palatability
  • Swallowability
  • Absorption
  • Stability
• Cons of emulsions

  • Patient compliance
  • Dosage accuracy
  • Storage conditions
  • Microbial contamination
  • Transportation
• Tests to determine emulsion type

  • Dilution test
  • Dye test
  • Electric conductivity test
• HLB system

  • Hydrophile-lipophile balance
  • Calculate the relative quantity of emulsifiers needed to produce a stable emulsion
  • Surfactant has HLB numbers which represent the relative proportions of the lipophilic and hydrophilic parts of the molecule
• High HLB number

  Surfactant exhibiting hydrophilic or polar properties
• Low HLB number

  Surfactant exhibiting lipophilic or non-polar properties
• Optimum HLB

  Particle size of emulsion is at a minimum thereby contributing to the emulsion stability
• Stable emulsion

  System in which globules retain their initial character and remain uniformly distributed in continuous phase
• Stability issues

  • Cracking
  • Creaming
  • Phase inversion
• Cracking

  Separation of emulsion into 2 layers and indicates gross instability
• Creaming

  Incompatible with emulsifier and decomposition of, could be due to storage temperature
• Phase inversion

  Phase volume ratio is an important type of emulsion formed, excess amount of disperse phase