2. CONTENTS
Computers in pharmaceutical formulations
Development of pharmaceutical emulsions
Microemulsions as drug carriers
Reference
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3. INTRODUCTION
Formulation and development is a process
of selection of component and processing
Various technique such as design of experiments are
implemented for optimization of formulation and
processing parameter
Traditionally optimization refers to changing one
variable at a time
Many times finding the correct answer is not simple .
In such cases use of computer tools is the best way
to solve problem
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4. DEVELOPMENT OF
PHARMACEUTICAL EMULSIONS
Definition
An emulsion is a thermodynamically
unstable system containing mixture of two or more
immiscible liquids which is stabilized by adding
emulsifying agent.
Phases of emulsion
Discontinuous phase
Continous phase
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5. TYPES OF EMULSIONS
Based on dispersed phase
Oil in water(o/w)
Water in oil (w/o)
Water in oil in water(w/o/w)
Based on size of liquids
Macroemulsions
Microemulsions
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6. EMULSIFYING AGENTS
An emulsifying agent is any material
that enhances the stability of an emulsion
Mainly 3 types
Surfactants- Eg: SLS, Cetrimide
Hydrocolloids- Eg: Acacia, Tragacanth
Finely divided solids- Eg : Bentonite
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7. THEORIES OF
EMULSIFICATION
Film theory:
The added emulsifying agent forms a mechanical film
by getting adsorption
Viscosity theory:
↑in viscosity,↑in stability
Wedge theory:
Monovalent soap gives o/w emulsion,divalent soap
gives w/o emulsion
Interfacial theory:
The added emulsifying agent reduces the interfacial
tension
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8. STABILITY OF EMULSIONS
Most common stability problems are
Creaming and sedimentation:
As the droplets are subjected to gravity
force,they tend to move upward (creaming) or
downward(sedimentation)
Cracking or coalescence:
Is the fusion of 2 or more droplets of the
disperse phase forming one droplet
Phase inversion:
Emulsion changes from one type to another
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9. METHODS TO ENHANCE
STABILITY
Globule size:
smaller particles have slower creaming or
sedimentation
Viscosity of continuous phase:
↑in viscosity ↑stability
Using emulsifying agent:
Enhance viscosity,reduce interfacial tension
Storage of temperature:
↑ in temp,↓ stability
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10. METHODS FOR EVALUATION OF
STABILITY OF EMULSIONS
Size frequency analysis by microscopy
Velocity of craming
Globule size analysis
Turbidimetric analysis
Conductivity testing
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11. METHODS OF
PREPARATION
Dry gum method
• Triturate emulsifier+oil
• Add water
• Triturate and form primary emulsion
• Add remaining qty of water
Wet gum method
• Triturate gum+water
• Add oil and form primary emulsion
• Add remaining qty of water
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12. METHODS OF
PREPARATION
Bottle or Forbes bottle method
Gum+oil
↓
shake
↓
Add water
↓
Shake to form primary emulsion
↓
Add remaining qty of water
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13. APPLICATIONS OF
EMULSIONS
Oral administarion of water insoluble liquids
IV administration of API as an emulsion(Taxol)
For external use(lotions,liniments)
Emulsions in aerosol can be used to produce
foam
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16. MICROEMULSION AS A DRUG
CARRIER SYSTEM
Improved drug solubilization
Long shelf life
Ease of preparation
Improved bioavailability
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17. DISADVANTAGES
Stability is influenced by environmental
parameters such as temperature and ph
Limited solubilizing capacity for high melting
substances
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18. TYPES OF
MICROEMULSIONS
Direct microemulsion:
Droplets are dispersed in the
continuous aquous phase
Reversed microemulsion:
Water droplets are dispersed in the
continuous oil phase
Bicontinuous microemulsion:
Micro domains of oil and water are
interdispersed within the system
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19. THEORIES OF
MICROEMULSION
Thermodynamic theory
The free energy of microemulsion formation can be
dependent on the extent to which surfactant lowers the surface
tension of oil-water interface
DGF=ˠDA-TDS
Solubilization theory
Formation of microemulsion by micelles gradually
become larger and swells to a certain size range results
Interfacial theory
Microemulsion is capable of forming negative
interfacial tension
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21. PREPARATION
Drug has to dissolve in to oil phase of microemulsion
Water phase is combined with surfactant and cosurfactant
The amount of surfactant and cosurfactant to be added in the oil
phase is determined with the help of pseudoternary phase diagram
Ultrasonicator can finally used to achieve the desired range for the
dispersed phase
It is then allow to equilibrate
Gel may be prepared by the addition of gelling agent to above
microemulsion
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22. APPLICATIONS
Dry cleaning process
Pesticide formulation
Floor polishers and cleaners
Cutting oils
In industry for the synthesis of polymers
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