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Pharmaceutics II Exam 1 > Heterogeneous Dispersion: EMULSIONS > Flashcards

Heterogeneous Dispersion: EMULSIONS Flashcards

1
Q

define an emulsion

A

a dispersion in which the dispersed phase is composed of small droplets of a liquid dispersed throughout a vehicle in which it is immiscible

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2
Q

according to the USP definition of emulsions:

emulsions are ______ systems in which….

A

emulsions are TWO-PHASE systems in which one liquid is dispersed throughout another liquid in the form of small droplets

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3
Q

what are the “2 phases” of an emulsion

A

internal phase (discontinuous) and external phase (continuous)

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4
Q

the internal phase is ____ while the external phase is _____

A

internal phase = dispersed liquid droplet (discontinuous)

external phase = dispersion medium (continuous)

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5
Q

in an O/W dispersion, _____ is the dispersed phase and ____ is the continuous phase

A

dispersed phase = oil
continuous = water

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6
Q

what is the dispersed particle size of an emulsion? can emulsions be injected?

A

0.1-100 micrometers in diameter

larger than an RBC, but we can still inject because they are LIQUID DROPLETS not SOLID PARTICLES (like suspensions)

emulsions must be injected slowly

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7
Q

true or false

emulsions are thermodynamically stable

A

FALSE

they are thermodynamically unstable

this is due to the fact that the droplets are small –> large surface area —> large surface tension

the surfactant TEMPORARILY reduces surface tension

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8
Q

true or false

emulsions exhibit coalescence

A

true (when small particles merge)

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9
Q

what are the emulsifying agents that can be used in an emulsion?

A

3 types:

-surfactants
-hydrophilic colloids
-finely divided solid particles

(finely divided solid particles is normally not used bc emulsions are LIQUID dispersed in liquid)

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10
Q

true or false

emulsions are two phase systems

A

true

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11
Q

N-cetyl N-ethyl morpholinum ethosulfate is also known as…..

A

Atlas G-263
cationic surfactant
forms o/w emulsion

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12
Q

a high HLB value usually means a o/w or w/o emulsion?

A

o/w

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13
Q

what is something to consider when choosing surfactants as emulsifying agents?

A

some may carry out an anionic/cationic charge which may not be compatible with the formulation.
therefore, a non ionic surfactant agent might be preferred

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14
Q

name 2 non-ionic surface active agents used as emulsifying agents

A

Atlas Span 80 (Sorbitan mono-oleate)
Atlas Tween 80 (polyoxyethylene sorbitan mono-oleate)

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15
Q

name 2 hydrophilic colloids and their properties

A

acacia and gelatin (NATURAL)

forms o/w emulsion

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16
Q

Atlas Span 80 and Atlas Tween 80:

o/w or w/o? what are their chemical names?

A

Atlas Span 80 = w/o
Atlas Tween 80 = o/w

Atlas Span 80 = sorbitan mono-oleate

atlas tween 80 = polyoxyethylene sorbitan mono-oleate

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17
Q

name 3 examples of “finely divided solid particles” used as emulsifying agents, as well as if they are o/w or w/o

A

bentonite
veegum
carbon black

bentonite = o/w and w/o
veegum = o/w
carbon black = w/o

carbon black is an adsorbent and not really used in ceutics

bentonite and veegum work by coating the surface of the particles and preventing aggregation

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18
Q

salts of d-glucuronic acid

A

acacia

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19
Q

hydrated aluminum silicate

A

bentonite

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20
Q

polypeptides and amino acids

A

gelatin

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21
Q

magnesium aluminum silicate

A

veegum

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22
Q

which has a high HLB value – Atlas Span 80 or Atlas Tween 80?

A

Atlas Tween 80.
good for o/w emulsions

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23
Q

what are 3 routes in which emulsions can be administered

A

oral
topical
parenteral

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24
Q

name 4 applications of emulsions in terms of oral administration

A

-can enhance bioavailability of water-insoluble drugs

-improve drug stability

-improvement of palatability

-laxative emulsion

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25
Q

as mentioned, emulsions can enhance the bioavailability of water insoluble drugs

give an example of this

A

Vitamin A is difficult to dissolve in water, but it will dissolve easier in an o/w emulsion

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26
Q

as mentioned, emulsions can improve drug stability.
give an example of this

A

erythromycin

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27
Q

give an example of a laxative emulsion

A

mineral oil

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28
Q

as mentioned, emulsions can improve the palatability of a drug

give a specific example of this

A

valproic acid is very bitter. When dissolved in oil, the taste won’t be noticeable

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29
Q

true or false

only O/W emulsions are widely used topically, not W/O

A

FALSE

they’re both widely used depending on the effect desired

W/O emulsions are OCCLUSIVE (create physical barrier) and EMOLLIENT (soothe. soften)

O/W emulsions are removed more easily by water

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30
Q

give 3 examples of how emulsions are given parenterally

A

IV nutrient emulsions (solution preferred but some pts can’t have dextrose)

antineoplastic agents (anticancer – methotrexate emulsion.) prolong action and minimize dosing frequency

influenza vaccine emulsion

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31
Q

what is the size of a RBC

A

~7 micrometers

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32
Q

give 3 examples of IV nutrient emulsions

A

cotton seed oil
dextrose
lecithin

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33
Q

name 4 advantages of emulsions

A

-therapeutic properties and spreading ability increases

-unpleasant taste or odor of an oil is masked

-absorption/penetration of drugs controlled (depending on o/w or w/o)

-aqueous and oil soluble drugs can be administered SIMULTANEOUSLY

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34
Q

true or false

emulsions can increase drug stability

A

TRUE

many drugs are more stable in emulsion rather than aqueous.
hydrolysis is more easily avoided

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35
Q

how can emulsions prolong drug action?

A

IM and SUBQ injections.
the drug can partition between the oil and water phases

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36
Q

how can the activity of a drug be maintained or enhanced in an emulsion?

A

through the partitioning of the drug from the oil phase to the water phase

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37
Q

there are ___ components in an emulsion:

A

3 components:

-oil phase
-water phase
-emulsifying agent

38
Q

the smaller the particle size, the ____ the surface energy.
what is the job of the surfactant?

A

HIGHER

job of surfactant (emulsifying agent) is to reduce this energy

39
Q

what are the 3 theories of emulsification

A

surface tension theory
oriented wedge theory
plastic or interfacial film theory

all have same meaning— surface tension, interfacial tension, surfactants, wetting agents

40
Q

name the 4 desirable properties of emulsifying agents

A

-be surface active and REDUCE SURFACE TENSION TO BELOW 10 DYNES/CM

-be adsorbed QUICKLY around the dispersed droplets. (a condensed, nonadherent film will prevent coalescence)

-impart to the droplets enough electrical potential so that MUTUAL REPULSION occurs

-be effective in a REASONABLY LOW CONCENTRATION (surfactants considered toxic)

41
Q

one of the desirable properties of emulsifying agents is to impart to the droplets an adequate electrical potential so that mutual repulsion occurs

are there any potential problems with this?

A

yes
the charge might have an interaction with the drug formulation. sometimes nonionic is preferred

42
Q

Span 40
Span 60
Span 65
Span 80

rank them according to HLB value (highest to lowest)

A

highest HLB = Span 40
Span 60
Span 80
Lowest HLB = Span 65

43
Q

Tween 20
Tween 60
Tween 80

rank them according to HLB value (highest to lowest)

A

highest = Tween 20
Tween 80
lowest = tween 60

44
Q

which have higher HLB – span or tween?

A

tween

45
Q

are span and tween natural or synthetic emulsifying agents?

A

synthetic

46
Q

name some natural emulsifying agents

A

gelatin
egg yolk
casein
wool fat
cholesterol
lecithin

47
Q

Sorbitan tristearate

A

span 65

48
Q

sorbitan monostearate

A

span 60

49
Q

sorbitan monooleate

A

span 80

50
Q

sorbitan monopalmitate

A

span 40

51
Q

polyoxyethylene sorbitan monolaurate

A

tween 20

52
Q

polyoxyethylene sorbitan monostearate

A

tween 60

53
Q

polyoxyethylene sorbitan monooleate

A

tween 80

54
Q

what is the desired HLB for a w/o emulsion

A

3-6

55
Q

what is the desired HLB for o/w emulsions

A

8-18

56
Q

what is the desired HLB for detergents

A

13-15

57
Q

what is the desired HLB for antifoaming

A

1-3

58
Q

what is the desired HLB for wetting agents

A

7-9

59
Q

what is the desired HLB for solubilizers

A

15-20

60
Q

explain why we would use 2 surfactants

A

sodium cetyl sulfate is an anionic surfactant. if we just used that, there would be a lot of empty space around the oil droplet due to the repulsion of like charges. thus, we can use a nonionic surfactant (such as cholesterol) to fill in the gaps.

the ultimate goal is to lower the interfacial tension below 10 dynes/cm

if the gaps weren’t filled in, adjacent particles would aggregate (coalescence)

61
Q

is cetyl alcohol + sodium oleate a good combination of surfactants?

A

no

62
Q

is sodium cetyl sulfate + oleyl alcohol a good combination of surfactants?

A

no

63
Q

is sodium cetyl sulfate + cholesterol a good combination of surfactants?

A

yes

64
Q

what are the 3 methods of emulsion preparation?

A
  1. continental/dry gum method
  2. english/wet gum method
  3. bottle/forbes bottle method
65
Q

explain the continental/dry gum method

A

used to prepare emulsions

primary emulsion is made of:
fixed oil, water, acacia in 4:2:1 Ratio

oil is added to the acacia and the micture is titurated until the powder is evenly distributed throughout the oil. forms a PASTE

water is then added all at once followed by rapid tituration to form the PRIMARY EMULSION

any remaining water + other ingredients are added to finish the product

66
Q

in the continental/dry gum method, the last step is to add any remaining water and other ingredients to finish the product

explain this further

A

electrolytes (in high concentration) tend to crack an emulsion, thus they should be added LAST in as dilute a form as possible

also, alcoholic solutions tend to dehydrate and precipitate hydrocolloids, so they should be added in as dilute a concentration as possible

67
Q

explain the english/wet gum method for preparing emulsions

A

-primary emulsion of fixed oil, water, acacia in a 4:2:1 ratio

2 parts of water are added all at one to 1 part of acacia and the mixture is titurated until a smooth mucilage (glue) is formed

then, oil is added in small incremements (1-5mL) with continuous tituration until the primary emulsion is formed

the mixture is titurated for another 5 mins (o/w) and can be brought up to volume with water and mixing

68
Q

explain the bottle/forbes bottle method of preparing emulsions

A

oil is added to acacia in a bottle

ratio of oil:water:acacia is 3:2:1 OR 2:1:1

69
Q

why is the ratio of oil:water:acacia 4:2:1 in the dry gum/wet gum methods, but in the bottle/forbes bottle method it is 3:2:1 or 2:1:1?

A

because the low viscosity of the volatile oil used in the bottle method requires a higher proportion of acacia

70
Q

is a mortar and pestle used for all 3 methods of preparing emulsions?

A

NO

only the dry and wet gum methods

71
Q

a stable emulsion is defined as…..

A

an emulsion that would maintain the same number of dispersed particles per unit volume of the continuous phase

72
Q

what is creaming?

A

the creaming of emulsions is when the dispersed particles/droplets rise or sediment (depending on the differences in densities between the phases)

73
Q

how can the creaming emulsion be reconstituted?

A

by shaking

74
Q

the rate of creaming is _______ proportional to the viscosity of the emulsion

A

inversely

ie: high viscosity = low rate of creaming

75
Q

the _____ droplets cream more rapidly than _____ ones

A

LARGER DROPLETS CREAM MORE RAPIDLY THAN SMALLER ONES

76
Q

how can aggregation/coalescence of emulsion droplets be prevented?

A

by forming a thick interfacial film (in the use of macromolecules like natural gums or protein)

or finely divided solids (veegum and bentonite)

77
Q

besides creaming and coalescence, what are 3 other considerations for the stability of emulsions?

A

temperature, microorganisms, alcohol content

alcohol may cause dehydration and everything will crack

78
Q

what are microemulsions?

A

liquid dispersions of water and oil that are made HOMOGENEOUS, TRANSPARENT, AND STABLE by the addition of a relatively large amount of surfactant and cosurfactant

79
Q

true or false

emulsions are homogeneous, transparent, and stable

A

FALSE – only microemulsion

80
Q

what is the droplet diameter of microemulsions?

A

~100-1000 angstroms

81
Q

true or false

like normal emulsions, microemulsions can be W/O or O/W

A

true

82
Q

true or false

microemulsions are thermodynamically stable

A

TRUE

bc of the large amount of surfactant

83
Q

can microemulsions be given IV?

A

yes

84
Q

which has a higher bioavailability – microemulsions or conventional emulsions?

A

microemulsions

85
Q

can surfactants enhance absorption?

A

YES they can enhance permeation through the reduction of interfacial tension – affect the absorption rate of the drug

86
Q

are span and tween natural or synthetic?

A

synthetic

87
Q

is an emulsifying agent used in all 3 methods of emulsion preparation?

A

NO
acacia is used in dry and wet gum, but none is used in the bottle method
mixing is done in the bottle method to reduce the particle size. emulsifying agent not used

88
Q

besides the main 3 methods of preparing emulsions, name 2 others

A

auxiliary methods
in situ soap method

89
Q

name 4 equipment pieces used in emulsification

A

high speed mixer
blenders
colloid mills
homogenizers

they all give energy to reduce the particle size

90
Q
A

Pharmaceutics II Exam 1 (9 decks)

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