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PHAR 224 > Emulsions > Flashcards

Emulsions Flashcards

1
Q

What is an Emulsion?

A

Dispersed system containing 2 insoluble liquids

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2
Q

Droplet size for emulsions?

A

0.1-100 um

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3
Q

Define a O/W Emulsion

A

Oil droplets dispersed in water/aqueous phase with water >45% of total weight

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4
Q

Define W/O emulsion

A

water droplets dispersed in oil phase, water<45% of total weight

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5
Q

Can you have multiple emulsions?

A

Yes, W/O/W, O/W/O; an emulsion within an emulsion

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6
Q

What are advantages of using emulsions as a dosage form?

A
  • Administration of unpalatable drugs
  • aqueous phase easily flavored
  • oily sensation easily removed
  • increase rate of absorption
  • easy parenteral admin where liquid phase is important
  • possible to include 2 incompatible ingredients
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7
Q

Type of Emulsion for Oral Admin?

A

Mostly O/W to ensure pleasant taste

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8
Q

Type of emulsion for IV admin?

A

Must be O/W b/c serious embolization may occur

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9
Q

Type of emulsion for IM admin?

A

Usually W/O for depot therapy (sustained release)

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10
Q

Characteristics of O/W external use emulsions?

A

Not Greasy
water-washable

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11
Q

Characteristics of W/O external use emulsions?

A

Greasy
occlusive
form water-repellent film

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12
Q

Advantages of using O/W oral emulsions?

A

Mask taste
Render oil more digestible
Increase bioavailability of the drug by icreasing the solubility

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13
Q

Most common dosage form for emulsions?

A

Topical formulation

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14
Q

What emulsion type would you use for unbroken skin?

A

W/O –> easily spreads

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15
Q

What type of Emulsion is a Lotion?
Ointment?
Cream?

A

Lotion: O/W
Cream: both
Ointments: W/O

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16
Q

Oil phase choices for Oral?

A

Liquid paraffin
Castor oil
cod liver oil
arachis oil
–> all of these are laxatives

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17
Q

oil phase for IV?

A

Cottonseed oil
soya bean oil
safflower oil

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18
Q

Oil phase for external use?

A

Turpentine oil
benzyl-benzoate
various oils as carriers for AI –> liquid paraffin

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19
Q

What are fixed oils? Exs?

A

non-volatile/fatty oil of anomal or plant derivations, a mixture of esters of fatty acids, TGs.
Ex: Castor oil, cod liver oil, olive oil

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20
Q

Essential or volatile oils? Exs?

A

non-fatty oils from plants
Ex: mint oil, rose oil, peppermint oil

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21
Q

Mineral Oil? Exs?

A

a grade of liquid petrolatum
Ex: liquid paraffin

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22
Q

Water phase Exs?

A

Water
Glycerol
Propylene glycol
Polyethylene glycols
Sorbitol

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23
Q

How do emulsifiers stabilize the system?

A

reduce the inferfacial tension
imparting a charge on the droplets creating electrostatic repulsion

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24
Q

What are requirements for emulsifying agents?

A

Molecular structure
stabe interface
chemical stability
inertness
non-toxic
non-irritating
odorless
tasteless
colorless
not cost-prohibitve

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25
Q

Classes of emulsifying agents?

A

Chemical structure:
- synthetic and semi-synthetic
- Natural
- Finely dispersed solids
- Auxillary agents
MOA:
- surface active agents
- hydrophilic colloids
- finely divided solid particles

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26
Q

Most common emusifying agents?

A

Surfactants:
- anionic
- cationic
- non-ionic
- zwitterionic

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27
Q

What structural classification do polymers and surfactants fall under?

A

Synthetic

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28
Q

WHat are semi-synthetic emulsifying agents derived from?

A

cellulose

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29
Q

Types of anionic surfactants?

A

Soft soaps: alkali metal and amminium soaps
Hard Soaps: divalent and trivalent metals
Detergents: sulfated and sulfonated compounds

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30
Q

Most common anionic surfactant? why?Ex?

A

Detergents b/c resistant to hydrolysis
Ex: Sodium lauryl sulfate

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31
Q

What area has the negatvie charge for anionic surfactants?

A

The hydrophilic head

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32
Q

What area has the positive charge for cationic surfactants?

A

The hydrophilic head

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33
Q

What other purpose are cationic surfactants used for opthalmically?

A

As a preservative/ antiseptic/ disinfectant

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34
Q

What is a non-ionic surfactatn where a hydrophobic portion predominates soluble in?

A

Oil-soluble

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35
Q

What is a non-ionic surfactatn where a hydrophillic portion predominates soluble in?

A

Water-soluble

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36
Q

What are some Exs of non-ionic surfactants?

A

Sorbital esters (SPANS) and Polyoxyethylene sorbitan esters (TWEENS)

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37
Q

Most common surfactants?Why?

A

Non-ionic
Neutral pH, resistant to added acids and electrolytes, superior in compatibility, stability, ands saftey

38
Q

What is the cationic part of synthetic zwitterionic surfactants?

A

Primary/Secondary/tertiary amines or ammonium

39
Q

Which area is variable for zwitterionic surfactants?

A

Anionic area

40
Q

How do finely divided solids work as emulsifying agents

A

form particulate layer around dispersed droplets, swell in dispersion medium, increase inter-particle distance, minimize inter-particle interaction

41
Q

What does the viscosity depend on for finely divided solids?

A

the internal concentration, relative volume of the internal phase

42
Q

What are auxillary emusifiers? How do they work?

A

weak emulsifiers used always in combonation with other emulsifiers.
Stabalize system by thickening (increasing viscosity)

43
Q

When do you use cationic emusifiers? Anionic?

A

Cationic –> low [ ] b/c can become toxic, used when antiseptic properties are required
Anionic have high pH, do not use for broken skin

44
Q

Are Ionic emulsifiers used orally?

A

No; irritant to GIT

45
Q

What surfactants are used in parenteral use?

A

Non-ionic, specific ones such as lecithin and polysorbate 80

46
Q

What 2 structural features are common in all types of surfactants?

A

Hydrophillic head, hydrophobic tail

47
Q

Mono-molecular film?

A

Move to liquid: liquid interface
reduce surface interfacial tension as higher [ ] at interface comared to bulk mixture
–> surface active agent

48
Q

Multi-molecular film?

A

protection from coalescence via:
- protective sheath around droplets
- imparting charge on droplets, repulsion
- wetting to increase viscosity
no change in interfacial tension
–> hydrocolloids

49
Q

Solid particle film?

A

Form particulate layer, swells, increase viscosity, impair droplet movement
–> finely divided solids

50
Q

How do surfactants impact interfacial tension?

A

Lower it

51
Q

What is the CMC?

A

Critical micelle [ ] –> [ ] of surfactant above which micelles form and all additional surfactants added to the system will form micelles

52
Q

What is the aggregation number?

A

average number of surfactant monomers in a spherical micelle

53
Q

do ionic surfactants require more or less [ ] to form micelles than non-ionic?

A

Ionic require much more [ ] than non-ionic

54
Q

What is the dynamic equilibrium within the system with micelles?

A

Micelles in dynamic equalibrium with monomeric surfactant molecules in the emulsion

55
Q

Do you want an emuslifier with a low CMC?

A

No, surfactant will form micelles before oil droplets can be coated

56
Q

What does low HLB value mean?

A

low polarity, lipophilic surfactant (0-10)

57
Q

What does high HLB value mean?

A

high polarity, hydrophilic surfactant (10-20)

58
Q

WIth same oil how can HLB values differ based on w/o, o/w?

A

w/o emulsion will desire a low HLB value
o/w will desire a high HLB value

59
Q

How do you calculate HLB of a mixture?

A

HLB(mixture) = y x HLBa + (1-y) x HLBb

60
Q

How do you mix the oil and water phase?

A

Always water into oil slowly

61
Q

What are antioxidants used for?

A

prevent auto-oxidation of oil and lipid components

62
Q

What do chelating agents do?

A

Grab up free ions

63
Q

Exs of true antioxidants?

A

BHA and BHT

64
Q

Exs of chelating agents?

A

EDTA, tartaric acid, citric acid

65
Q

What are chelating agents synergistic with?

A

reducing agents

66
Q

Major preservative used?

A

parabens

67
Q

What are Humectants? exs?

A

agents capable of absorbing water from the air, used to reduce evaporation of water phase
ex: propylene glycol, glycerol, sorbitol

68
Q

Dry gum method?

A

emulsifying agent into oil phase, make water phase, add water phase to oil phase = primary emulsion

69
Q

Wet gum method?

A

water + emulsifying agent = mucilage, add slowly to oil phase = primary emulsion

70
Q

would you use a glass mortor with natural emulsifying agents?

A

No, b/c natural need more enery to mix

71
Q

In situ soap method?

A

emulsifying agent is formed fresh inside the solution.
ex: cottonseed oil mix with lime water –> Calcium oleate as emulsifying agent = w/o emulsion

72
Q

Surfactant based method?

A

HLB claculated, SPAN in oil phase and TWEEN in water phase, SPAN and TWEEN amount depends on emulsion type w/o or o/w

73
Q

Mechanica stirrers use?

A

for low viscosity preparations, large quantities

74
Q

Homogenizers use?

A

small inlet orfice and pressure used to incorporate oil but, limited as cannot be used for viscosity greater than 2000 cP

75
Q

Ultrasonifers use?

A

ultrasonic waves break down emulsified droplets, produces a uniform emulsion

76
Q

What external labels are needed for emulsions?

A

shake well
–> external use only for topical

77
Q

What is a stable emulsion?

A

Dispersed droplets retain orignal characteristics and remain uniformly dispersed throughout the continuous phase

78
Q

What is creaming?

A

dispersed droplets move upward within the continuous phase

79
Q

What is sedimentation?

A

dispersed droplets move downward within the continuous phase

80
Q

How can you reduce the rate of creaming/sedimentation?

A

decrease droplet size
decrease the density difference between the 2 phases
increase viscosity of the continuous phase
control the disperse phase [ ]

81
Q

Can emulsions that have creamed or sedimented be redispursed?

A

Yes

82
Q

what does a negatvie calue of v in stokes law indicate?

A

indicates upward movement = creaming

83
Q

What do particles in the primary maximum zone show?

A

higher energy of repulsion vs attraction = more likely to remain separated or deflocculated

84
Q

Is to much repulsion dangerous?

A

yes, can increase the risk of attraction betwee the third and second particle

85
Q

What is coalescence?

A

complete fusion of droplets within an emulsion, leading to an ultimate separation of the 2 insoluble phases

86
Q

How is coalescence resisted in o/w? w/o?

A

resistance provided by the strenght of mono or multimolecular films for o/w
presence of hydrocarbon chains of surfactant molecules which project into oil phase for w/o

87
Q

Is coalescence reversible?

A

NO

88
Q

BUD for simple external emulsons?

A

1 month

89
Q

What is the usual BUD for all water containing preparations when ingredients are in solid form and chemical stability of the system is unknown?

A

14 days

90
Q
A

PHAR 224 (7 decks)

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