Emulsion Flashcards
What is an emulsion?
Dispersion of two immiscible or partially miscible liquids where one is uniformly distributed as fine droplets within the other; both must be relatively stable + homogeneous
When are multiple phase emulsions used?
Often as modified/slow release dosage forms
What is generally needed as a third phase in multiple phase emulsions?
An emulsifying agent; required to stabilize emulsions
How are emulsions administered?
Oral
Topical
Parenteral
Oil in water emulsions mask what?
Foul tasting oils
How would you make the oil more digestible and readily absorbed?
Globule size reduction
What does a globule size reduction do to the oils?
Makes them more digestible and readily absorbed
What kind of emulsion is more easily removed by water?
Oil in water
What kind of emulsion can be applied more evenly?
Water in oil
(T/F) Advantages of Emulsion
Poorly water soluble drugs may be easily incorporated
True
(T/F) Advantages of Emulsion
Does not do much to mask unpleasant taste/odor of oils
False; it does mask
(T/F) Advantages of Emulsion
Enhanced abosorption
True
What is the surface tension theory?
Assumes a shape to minimize their surface area
According to the surface tension theory, when two or more drops of the same liquid come into contact, what is thermodynamically favorable?
To coalesce, form one large drop to reduce surface area
According to the surface tension theory, what do surfacants, emulsifiers, or wetting agents do?
Encourage liquids to disperse into smaller drops
Lowers interfacial tension of two immiscible liquids + reduce repellent force while lowering liquids attraction for its own molecules
According to the surface tension theory, by _______ interfacial tension, surfactants, emulsifiers help convert large globules into smaller ones that have a _____ tendency to reunite/coalesce
lowering
lower
What is the oriented wedge theory?
Surfactant/emulsifying agents form monolayers around droplets of the internal phase of the emulsion to prevent coalescence
What is the plastic or interfacial film theory?
Emulsifier forms an interface between the oil and water
According to the oriented wedge theory, a wedge encompasses the globules preventing _____
coalescence
According to the plastic or interfacial film theory, what prevents the contact and coalescing of the dispersed phase?
film
According to the plastic or interfacial theory, what must the film be able to do to each drop?
Coat the entire surface
According to the plastic or interfacial theory, water-soluble agents encourage what kind of emulsions?
Oil in water
Vice versa for the other way around
In reality, what is the caveat behind all three theories?
None individually explain the mechanism by which emulsifiers form and stabilize emulsions
It is very likely that these theories simultaneously play a part (T/F)
True
When picking an emulsifier, what should it be?
- Stable
- Non-toxic
- Little to no odor, taste or color
- Proper HLB balance
Carbohydrates form what emulsions?
Oil in water
What are examples of carbohydrate emulsifying agents?
Acacia
Proteins form what emulsions?
Oil in water
What are examples of protein emulsifying agents?
Gelatin
High molecular weight alcohol form what emulsions?
Oil in water
Cholesterol forms what kind of emulsion?
Water in oil
Surfactants + wetting agents may be:
- Non-ionic
- Ionic
- Anionic
- Cationic
- Zwitterionic
All except ionic
Surfactants + wetting agents form what emulsions
Both kinds
Emulsions are considered physically unstable if:
- Globules tend to form upon standing
- Large globules rise/sink to form a concentrated layer
- Ostwald ripening
Large globules rise/sink to form a concentrated layer is known as….
creaming
Is creaming reversible?
Yes
How can you reduce creaming?
- Form smaller particles
- Increase viscosity
- Decrease density difference
What is Ostwald ripening?
Diffusion of material from smaller to larger droplets in the continuous phase
When is Ostwald ripening most often observed in?
water in oil
Which temperature should you protect emulsions from?
Extreme cold + heat
What does freezing/heating do to emulsions?
Separation and coalescence of the internal phase
When is temperature a issue in emulsions?
Shipping/storage, time of year, different countries
How can small-scale emulsions prepared by?
- Mortar/pestle
- Blender
- Simple prescription bottle
What are the two small-scale emulsion methods?
- Dry gum method
2. Wet gum method
Dry gum method is referred to as the ________ method
4:2:1
4 x oil, 2 x water, and 1 x emulsifying agent
What is the usual emulsifying agent for the dry gum method?
Acacia gum
How is the wet gum method different from the dry gum counterpart?
Order is different
After the viscous paste is made, it is followed by a slow addition of the oil
Higher HLB numbers means the more _______ the surfactant/emulsifying agent
hydrophilic
HLB values are ______ additive
algebraically
What is trituration?
Process of grinding to a fine powder in the dry state
What is Levigation?
Process of grinding an insoluble substance to a fine powder while wet
What is the levigating agent?
Liquid that is used to grind the insoluble material
While levigation is happening, powder being ground must not be ____ in the liquid
soluble
HLB values of 3-6 are greatyl _______ and produce ______ emulsions
Lipophilic
water in oil
HLB values of 8-18 are greatly _______ and produce ______ emulsions
hydrophilic
oil in water
