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Pharmacy Practice Lab II > Lab 6 Part 1 > Flashcards

Lab 6 Part 1 Flashcards

1
Q

define an emulsion

A

a mixture of two immiscible liquids where one phase is finely dispersed in the other and stabilized using an emulsifier

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2
Q

as mentioned, an emulsion is a mixture of 2 immiscible liquids where one phase is finely dispersed in the other and stabilized using an emulsifier.

the 2 immiscible liquids are generally what?

A

oil and water

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3
Q

the liquid dispersed in the other liquid is called the ___ or ___ phase

A

dispersed or internal phase

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4
Q

the liquid in which the other is dispersed is called the __ or __ phase

A

continuous or external phase

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5
Q

emulsions are classified in ___ types:

A

2 types based on whether the water or oil is dispersed as the fine droplets

o/w – oil is dispersed phase, water is external

w/o – water is dispersed phase and oil is external

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6
Q

are there any other types of emulsions besides w/o or o/w?

A

yes:

multiple emulsions (emulsion dispersed within an emulsion) w/o/w or o/w/o

microemulsion (droplet size less than 200nm)

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7
Q

multiple emulsions and micro emulsions are generally prepared using what?

A

commercial technology

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8
Q

what 2 tests are used to determine the type of emulsion

A

dilution and dye tests

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9
Q

explain how the dilution method to determine the type of emulsion works

A

when water is added to a w/o emulsion, the water is not incorporated in the emulsion and remains as a second layer

in the case of an o/w emulsion, a separate oil layer would be observed

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10
Q

explain how the dye method of determining the type of emulsion works

A

when a dye that is soluble to the external phase is added, the dispersed phase will look like colorless droplets when viewed under a microscope

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11
Q

name 3 ways in which emulsions can be administered

A

orally
IV
topical

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12
Q

name some emulsions that can be administered orally

A

mineral oil
oil soluble vitamins
products for enteral feeding

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13
Q

what emulsions can be given IV

A

IV lipids

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14
Q

what emulsions can be given topically

A

ointments
creams
lotions

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15
Q

oral emulsions are ___ ___

A

pourable liquids

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16
Q

oral emulsions are generally w/o or o/w? why?

A

generally o/w because the oily phase doesn’t taste as good and is also more difficult to flavor

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17
Q

true or false

emulsions for external applications are either water in oil OR oil in water and may be liquid or semisolid

A

true

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18
Q

topical ___/___ preparations are more occlusive and emollient while __/___ are easier to remove/wash

A

w/o are more occlusive and emollient

o/w are easier to remove/wash

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19
Q

emulsifers ____ the surface tension

why

A

emulsifiers LOWER the surface tension which helps to break up the large droplets into smaller ones and preventing their coalescence

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20
Q

what is the 1st theory of emulsification

A

the surface tension theory – emulsifiers lower the surface tension which helps to break up large droplets into smaller ones and prevent their coalescence

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21
Q

what is the oriented wedge theory

A

based on hydrophilic and hydrophobic properties

emulsifiers tend to orient their hydrophilic and hydrophobic portions between the external and internal phase (based on solubility)

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22
Q

according to the oriented wedge theory, an emulsifier that is more hydrophilic will form __ in ___ emulsion

why?

A

oil in water

this is because the hydrophilic portion is not large enough to form a wedge in the droplet

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23
Q

explain the interfacial film theory

A

the emulsifying agent is adsorbed on the surface of the dispersed droplets and thus prevents contact with the external phase

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24
Q

lowering of surface tension is important in the formation of the ________ and orientation and interfacial film theories are required to…..

A

lowering surface tension is important in forming the initial dispersion

oriented wedge and interfacial film are required to prevent COALESCENCE and thus maintain stability

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25
Q

in the HLB system, a diagram of an emulsifier will have the ____ portion as the head and the ___ portion as the tail

A

hydrophilic head and hydrophobic tail

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26
Q

____ devised a method to categorize the emulsifiers based on the ratio of hydrophilic and lipophilic portions in the emulsifier

A

griffin

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27
Q

what is the term for the “ratio” that griffin devised to categorize emulsifiers based on the ratio of hydrophilic and lipophilic portions in the emulsifier

A

HLB value

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28
Q

each emulsifier is assigned an HLB value to indicate its degree of _____

A

POLARITY (hydrophilicity)

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29
Q

which emulsifier is assigned a value of 1?
which emulsifier is assigned 40?

what do these values mean

A

1 = Oleic acid (LEAST POLAR)

40 = SLS (sodium lauryl sulfate) MOST POLAR

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30
Q

substances with an HLB ranging from 1-10 are used for….

A

antifoaming
water in oil
wetting properties

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31
Q

substances with an HLB value ranging from 10-20 are used to form….

A

oil in water emulsions

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32
Q

emulsifiers that have an HLB similar to that of the __ phase are used in preparing emulsions

A

oily phase

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33
Q

true or false

two or more emulsifiers CANNOT be used to achieve the desired HLB

A

false – you can use 2 or more to achieve the desired HLB

34
Q

HLB values 3.5-6

A

W/O emulsifier

35
Q

HLB values 7-9

A

wetting agent

36
Q

HLB values 8-18

A

O/W emulsifier

37
Q

HLB values 13-15

A

detergent

38
Q

HLB values 15-18

A

solubilization

39
Q

an emulsifier has 2 distinct actions:

A
  1. promote the formation of an emulsion - make easier to prepare by reducing droplet size and aid in stability
  2. controlling the type of emulsion – O/W or W/O
40
Q

the type of emulsion is related to the ____ of the emulsifier

A

HLB value

41
Q

the EFFICIENCY of an emulsifier is related to its….

A

chemical structure

(ester, partial ester, saturated lipophilic group, surfactatant)

42
Q

emulsifiers with an HLB value of ____ have EQUAL ATTRACTION TO OIL AND WATER

A

10

43
Q

Emulsifiers with an HLB value greater than 10 are more ___ and useful for which emulsion?

A

more hydrophilic and useful for o/w emulsions

44
Q

emulsifers with HLB values LESS than 10 are more ____ and used for which emulsions

A

hydrophobic and used for water in oil emulsions

45
Q

the HLB of the emulsifier used in the preparation depends on what 2 things

A

the HLB of the oil

the type of emulsion(w/o or o/w)

46
Q

lanolin anhydrous requires what HLB

A

for an o/w emulsion between 10-15

for a w/o emulsion 8

47
Q

why do we want to match the HLB value of the emulsifier to that of the oil

A

it results in a superior product that has better stability WHILE USING THE MINIMUM QUANTITY OF EMULSIFIER

48
Q

name the 3 types of emulsifiers available

A

natural products
finely divided solids
synthetic compounds

49
Q

____ and ___ are NATURAL emulsifiers and generally used for which emulsions?

A

gums obtained from trees (acacia, tragacanth)
gelatins

used for oral o/w emulsions

50
Q

name a type of finely divided solid emulsion.

what kind of emulsions do they form

A

clays

when added to water, form o/w when water volume is greater than the oil

51
Q

true or false

bentonite can also form w/o emulsions

A

TRUE

52
Q

name 3 types of synthetic surfactants

A

anionic
cationic
nonionic

53
Q

what kind of emulsions do synthetic surfactants form

A

form o/w or w/o

are used in TOPICAL PREPARATIONS

54
Q

TRUE OR FALSE

anionic and cationic surfactants are compatible

A

FALSE

The charges neutralize each other and they are incompatible

55
Q

true or false

emulsifiers should be stable and not deteriorate during storage

A

true

56
Q

besides being stable, name 4 other requirements for emulsifiers

A

non toxic
physically stable (taste, odor)
chemically stable
therapeutically compatible with the drug and other ingredients

57
Q

how can acacia be administered?
what is the significance of this?

A

can be administered orally but NOT iv

this shows that emulsifying agents are selected based on the intended route of administration as some toxic effects DIFFER dpeending on the route of administration

58
Q

what is microcrystalline cellulose used for

A

to increase viscosity and prevent the settling of the dispersed phase

59
Q

___________ are used in TOPICAL emulsions as thickening agents to stabilize emulsions

A

high molecular weight alcohols like stearyl alcohol and cetyl alcohol

60
Q

the _____, _____, and _______ properties of the API must be reviewed before selecting excipients

A

physical, chemical, and pharmaceutical properties

61
Q

besides physical, chemical, and pharmaceutical properties of the API, what else is important in the selection of the appropriate dose volume of the designed product

A

the knowledge of the target population and the recommended dose for the indication

62
Q

when the type of emulsion and the HLB required is determined, what is selected?

A

an emulsifier

63
Q

what is an important consideration about the container of an emulsion

A

there must be adequate free space for shaking

64
Q

emulsions mask…..

A

the disagreeable taste and odor of drugs

65
Q

what can you say about drug absorption and emulsions

A

drug absorption is enhanced through GI tract

66
Q

——— are injected IV in the form of emulsions

A

nutrient oils

67
Q

___________ preparations can be formulated in the form of emulsions

give 4 examples

A

topical

cold creams
shaving creams
turpentine liniment
benzyl benzoate

68
Q

how is a sustained release emulsion prepared

A

water soluble antigens and some drugs are formulated as water in oil type emulsions for IM DEPOT INJECTION PURPOSES (sustained release)

69
Q

what is creaming?
what kind of instability is it?

A

physical instability

movement of dispersed droplets either upward or downward (depending on the density of the phases). results in a non-homogeneous product – has 2 regions:
emulsion and cream

70
Q

the movement in creaming is based on….

A

stokes law

71
Q

true or false

creaming is irreversible

A

FALSE

reversible and shaking an redisperse the droplets unifmrly

72
Q

how can creaming be decreased

A

by reducing the droplet size and increasing the density of the external phase

73
Q

the rate of creaming increases when….

A

when the droplets aggregate to large droplets but do not fuse (flocculate)

74
Q

as mentioned, the rate of creaming is increased when the droplets aggregate but do not fuse (flocculate)

how can creaming in this way be prevented

A

an appropriate surfactant can be used to control the electrical charge on the aggregates and prevent creamins

75
Q

define coalescence

A

the fusion of droplets to larger globules

76
Q

what does coalescence lead to?

A

cracking

irreversible separation of the smulsion into 2 layers

77
Q

true or false

when an emulsion cracks, the product must be reformulated as the emulsion CANNOT be reformed upon shaking

A

true

78
Q

name 3 causes of cracking

A

-poor technique
-incompatiblity or degradation of the emulsifier
-change in storage temperature

79
Q

what is it called when an o/w emulsion concerts to a w/o emulsion and vice versa

A

phase inversion

occurs when dispersed phase is greater than 74% of the total volume

80
Q
A

Pharmacy Practice Lab II (12 decks)

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