Emulsions Lecture Flashcards
Define emulsions
Thermodynamically unstable
- Consist of two or more immiscible liquid phases: dispersed phase and dispersion medium
- Stabilized by emulsifying agents
Application and advantages of emulsions
Oral admin
- Reduced droplet size of oil globules make the oil more digestible and more readily absorbed
- Spread easily and completely over skin
- Irritation producing drugs
- More softening to the skin; resist drying
- Easily removed
Oral emulsions are? External are?
o/w
w/o
Define multiple emulsions
Droplet size of dispersed phase is smaller
- Miscible with continuous phase
- Prolonged action, taste masking, improved stability
- Putting two incompatible hydrophilic substance in te inner and outer aqueous phases separated by the middle oil phase
Two types of multiple emulsions
O/W/O
W/O/W
Define micro-emulsions
Stable
Transparent
Both o/w and w/o
Rapid and efficient oral absorption of drugs
Enhanced permeation through skin
Targeting of cytotoxic drugs to cancer cells
Dye test?
Water-soluble dye
O/w: distributes
W/O: clumps
Electrode tests?
Electrode in emulsions
O/W: passes through
W/O no current passes
Oral?
IV?
IM?
Semisolids?
O/W
O/W
W/O
Either
Oil phase to be used?
Affects the viscosity and spreadability
- Can be active agent
Define emulsion consistency
Texture and feel
w/o: greasy
- Allow dispensing from a flexible plastic container
Define emulsifying agents
Based on type, safety and route of admin
Non-ionic: not irritating
Ionic: irritating
Define Antioxidant
prevent oxidation of drugs and oil components
Define preservative
prevent the growth of microorganisms
Dry gum method
4 oil, 2 water, 1 gum
Acacia with oil then water
“primary emulsion”
Wet gum method
Acacia with water
Oil slowly
Bottle method
Acacia with oil then water
Industrial manufacturing
Subjected to high shearing and hydraulic forces
-Discharged and recirculated
Define creaming
flocs or aggregates rise to the top of the emulsion
- redistributed upon shaking
Define upward creaming
Dispersed phase is less dense than the continuous o/w
- negative velocity of sedimentation
Define downward creaming
Internal phase is heavier than teh external
w/o
Define density
greater the difference the larger the globules
Define viscosity
Less viscous the external phase, greater rate of creaming
Define coalescene
merge to form larger droplets
Define breaking
Separation of internal phase from extermal
- irreversible
- protective sheath breaks
Stabilization
Globule size should be reduced
- Density difference should be minimal
- Viscosity should be reasonably high
- Increased electrostatic repulsion
Storage
Protected from extreme cold and heat and outside stuff
Appropriate formulation and packaging
