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PHAR 224 > Emulsions > Flashcards

Emulsions Flashcards

1
Q

what is an emulsion

A

a dispersed system containing at least 2 immiscible liquids

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2
Q

what are advantages of an emulsion

A

Unpalatable drugs can be administered in palatable form
Aqueous phase easily flavored
Oily sensation easily removed
Increased rate of absorption
Ease of parenteral administration where lipid component (phase) is important
Possible to include two incompatible ingredients

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3
Q

oil phase for oral administration

A

Liquid paraffin
Castor oil
Cod liver oil
Arachis oil

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4
Q

oil phase for IV administration

A

cottonseed oil
cod liver oil
safflower oil

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5
Q

fixed oils

A

Castor oil
Cod liver oil
Olive oil

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6
Q

water phase

A

Water
Glycerol
Propylene glycol
Polyethylene glycols

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7
Q

requirements of an emulsifying agent

A 
Stable interface 
Chemical stability 
Inertness
Non-toxic, non-irritating
Odorless, tasteless, colorless
Not cost-prohibitive
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8
Q

plant derived emulsifying agents form what type of emulsion

A

Form o/w

Tragacanth, xanthan gum

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9
Q

animal derived emulsifying agents form what type of emulsion

A

Make o/w emulsions

Gelatin, cholesterol, lecithin Lanolin (w/o)

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10
Q

what are some semi-synthetic emulsifying agents

A

Methylcellulose, carboxymethylcellulose

Improve the stability of the emulsions by improving viscosity

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11
Q

polymer emulsifying agents

A

® PVP, PEG, or carbomer
o/w emulsions
Often viscosity building

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12
Q

soft soaps form what type of emulsion

A

Can be formed in situ
o/w emulsions
Sodium, potassium, ammonium, triethanolamine-stearate
Incompatible with electrolytes
ONLY ATTACH ONE FATTY ACID TO THE MONOVALENT IONS

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13
Q

hard soaps form what type of emulsion

A

w/o emulsions
Used to form w/o emulsions because the divalent ion can attach to more than one fatty acid meaning the hydrophobic portion is much more than the hydrophilic
Soluble in oil, water insoluble
Calcium oleate

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14
Q

detergents form what types of emulsions

A

o/w emulsion

Sodium lauryl sulfate

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15
Q

cationic surfactants are useful because

A

Not used very often as an emulsifying agent but is used for its antibacterial properties Quaternary ammonium compounds (benzylalkonium chloride, benethonium chloride)
Can be toxic in high concentrations because there are many negatively charged membranes in the body and these are permanently charged

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16
Q

non-ionic surfactants form what types of emulsions

A

◊ Can vary the size of the hydrophilic head and the hydrophobic tail
If hydrophobic portion predominates: surfactant is oil soluble
If the hydrophilic portion predominates: surfactant is water soluble
SPANS AND TWEENS

17
Q

zwitterionic surfactants are useful for what

A

injectables

ex: lecithin

18
Q

finely divided solids are used for what type of emulsion

A

most support o/w emulsions

19
Q

what are auxiliary emulsifiers?

A

Stabilize the system by thickening (increasing the viscosity)–>retard inter-particle movement
Ex: fatty acids (stearic acid), fatty alcohols (stearyl or cetyl alcohol) or fatty esters (glycerol mono stearate)

20
Q

what is the mechanism of action of surfactants?

A

Mono-molecular film:
Move to liquid: liquid interface–>higher concentration at interface compared to the bulk–>reduces the surface interfacial tension

21
Q

what is the mechanism of action of hydrocolloids

A

Multi-molecular film:
Causes NO change in interfacial tension and protects coalescence by:
Protective sheath around the droplets
Imparting charge to the droplets–>repel each other welling to increase viscosity–>less likely to merge

22
Q

what is the mechanism of action of finely divided solids

A

Solid particle film:

Forms particulate layer–>swells–>increases viscosity–> retards droplet movement

23
Q

Do you want a surfactant with a low CMC or high CMC value?

A

A surfactant with a low CMC means emulsifications is not as efficient as one whose CMC is higher
Low CMC are very potent and are attracted to one another and therefore form micelles instead of forming a micelle around the oil droplets
CMC is low–>surfactant will form micelles before oil (or water) droplets can be coated–>therefore a surfactant with a low CMC emulsification is not as efficient as one whose CMC is higher

24
Q

What does a low HLB value mean?

A

lipophilic surfactant
forms w/o emulsions
ie. SPANS

25
Q

What does a high HLB value mean?

A

hydrophilic surfactant
forms o/w emulsions
ie. TWEENS

26
Q

what is the formula to calculate the HLB value

A

HLBmix=x(HLBa)+(1-x)(HLBb)

27
Q

when making an emulsion does the water go into the oil phase or does the oil phase go into the water?

A

WATER GOES INTO THE OIL SLOWLY OR PHASE REVERSION CAN OCCUR

28
Q

when should antioxidants be used

A

when an oil other than mineral oil is used

29
Q

hydrophobic antioxidants

A

BHA, BHT, ascorbyl palmitate

30
Q

hydrophilic antioxidants

A

ascorbic acid

31
Q

what are examples of preservatives

A

Methylparabens (water phase) and propylparabens (oil phase)

32
Q

examples of humectants and when to use

A

topical formulations

EX: propylene glycol, glycerol

33
Q

labelling of emulsion

A

shake well

+/- external use only

34
Q

what is creaming

A

internal phase to the top (o/w) because oil is less dense

35
Q

what is sedimentation

A

internal phase to the bottom w/o because water is denser

36
Q

how to prevent creaming/sedimentation

A

Shake well
Decrease in droplet size (homogenization)
Decrease in the density difference between the two phases
Change the density of the hydrophilic phase: add glycerol or propylene glycol
Cannot change the density of the oil
Increase viscosity of the continuous phase (hydrocolloids)
Control of the disperse phase concentration

37
Q

what is flocculation

A

Process of aggregation of dispersed droplets into loose clusters within an emulsion

38
Q

what is coalescence

A

Coalescence is the complete fusion of droplets within an emulsion, which leads to a decreased number of droplets and ultimately separation of the two immiscible phases

39
Q

what should the BUD be on a emulsion

A

14 days with water containing products

1 month for external use preparations

PHAR 224 (7 decks)

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