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• Pharmacy topical formulations

  Composed of drugs in a semi-suitable base
• Pharmacy topical formulations

  • The base could be hydrophobic or hydrophilic
  • The base plays a role in drug release behaviour
• Ointments

  Preparation for external applications
• Ointments

  • Drugs are dissolved or dispersed in the ointment base
  • The ointment base could be anhydrous, greasy or immiscible with skin secretion
• Ointment base

  Mixture of waxes (solid, hard at RT), fats (semi-solid, soft at RT) and oils (liquid at RT)
• Preparation of ointment

  1. Melt vase in water bath, high MP to low MP

  2. As base cools add ingredients with decreasing melting point

  3. Stir continuously (homogenous mix) and leave to set
• Incorporation

  1. In liquid and semi solid state

  2. Pre-prepared ointment base

  3. Levigation or trituration
• Creams

  Viscous semi-solid emulsions
• w/o (oily creams)

  • Natural emulsifiers (bees or wool fat), creamy, white translucent and stiff, Emollient (moisturisers)
• o/w (aqueous cream)

  • Synthetic emulsifier (macrogol), Good for absorption and penetration of drug, Thin, white, smooth and water washable
• Preparation of creams

  1. Aqueous phase- dissolve the water-soluble ingredients and heat to 60 degrees

  2. Oily phase - melt the fatty bases and cool to 60 degrees

  3. Mix the two phases
• Pastes

  Semi solid preparation for external use
• Pastes

  • Very fine powders with a non-greasy base
  • Stiff and do not spread well
• Applications of pastes

  Localised delivery, dressing and nappy products
• Bases for paste

  White soft paraffin, liquid paraffin, glycerol and soaps
• Preparation of pastes

  Fusion, doubling up technique, levigation and trituration
• Gels

  Formed by aggregation of colloidal particles and polymers
• Gels

  • Often low conc of dispersed phase required
  • The drug is suspended in the matric and dissolved in liquid phase
• Colloidal particles

  Size less than 1 micrometre
• Colloidal domain

  Particle dispersions typically in size range 1nm to 1 micrometre
• Dispersed phase

  Particles or droplets
• Continuous phase

  Solution media
• Colloidal classification

  • Colloidal dispersion - particles droplets in dispersion medium, Thermodynamically unstable after separation
  • True solution of macromolecular materials - natural polymetric materials such as protein and cellulose, Stable thermodynamically and can be redispersed after phase separation
  • Associate colloids - surfactants and are thermodynamically stable
• Gel formation

  Particles linked together form an interlaced network
• Gel types - lyophobic sol gelation

  • Flocculation of sols (aluminium and magnesium hydroxide)
  • Bentonite
  • Kaolin
• Veegum

  Some sort of clay
• Veegum structure and hydration

  1. Silicon dioxide layer will delaminate

  2. Water knocks sodium ions away and delaminated it and the veegum gets in the solution

  3. Slightly positive edges are attracted to the negative faces forming house of cards

  4. Can track drug molecules within the house of card structure

  5. Control or sustain is release

  6. Forces are held together are van der waal which are weak
• Gel types - lyophilic sol gelation

  • Covalently bonded irreversible system with cross linked polymers
  • Held with weaker intermolecular bonds (hydrogen bonds) and are reversible (either heating or cooling)
• Gel type 1

  • Uses for fabrication of expanding implants for prolonged release for drug
• Gel type 2

  • PVA used as jellied for application of drug to skin
• Gelling agents

  • Clays, pectin, PVAs, gelatin, carbomers, alginates
• Gels

  • Stability, aesthetic, rapid release/absorption, suitable for topical application, easy to wash
• Pharmaceutical gels

  • Anaesthetic (tetracaine gel), skin condition (Bazuka gel), lubricant gels, spermicidal gels