emulsions Flashcards
(96 cards)
1
Q
What is an emulsion?
A
A two-phase system consisting of two immiscible liquids, one dispersed as droplets (USP) through-out another.
2
Q
to mix immiscible liquids and make an emulsion we need an ___
A
emulsifying agent
3
Q
dispersed phase
A
internal phase
4
Q
dispersion medium
A
external or continuous phase
5
Q
advantages of emulsions
A
- stable and homogenous mixture
- good palatability of distasteful oil in sweet flavored aqueous vehicle
- small oil globules are digested and absorbed well
-less irritation of skin
6
Q
based on viscosity emulsions are
A
liquids and semi-solids
7
Q
administration of emulsions
A
oral (liquid)
topical (liquid & semi-solid)
parenteral (liquid)
8
Q
What are the two types of emulsions?
A
Oil-in-water (O/W) and water-in-oil (W/O).
9
Q
factors determining emulsion type
A
- emulsifier
- phase ratio
- order of mixing
10
Q
emulsifier
A
favors a particular emulsion type
overcomes unfavorable phase ratio
11
Q
external phase
A
- greater concentration
- the one that is being added
12
Q
inversion of emulsion
A
O/W –> W/O and vice versa
13
Q
inversions happen due to
A
emulsion made by heating is being cooled
concentration of internal and/or external phases is changed
14
Q
internal concentration increases
A
inversion occurs
15
Q
stable emulsion
A
dispersed phase does not exceed 50% of total volume
16
Q
True or False: Emulsions are always stable.
A
False. Emulsions are (physically) thermodynamically unstable and require emulsifying agents.
17
Q
internal phase tends to form aggregates (globules)
A
upon standing
18
Q
The dispersed phase in an O/W emulsion is ____.
A
Oil.
19
Q
instability types
A
creaming
flocculation
coalescence
breaking
20
Q
creaming
A
migration of droplets of internal phase to top or bottom of emulsion
21
Q
creaming happens due to
A
improper dose (no longer even distribution)
22
Q
creaming is esthetically
A
unacceptable
23
Q
flocculation
A
small spheres of oil stick together to form flocs (larger drops)
drops remain separated
24
Q
___ is a prerequisite step to coalescence
A
flocculation
25
coalescence
merging of small droplets into large droplets
26
___ is coalescence and creaming combined
breaking
27
breaking
oil separates completely from the water
floats at the top as single continuous layer
additional emulsifier is needed
28
reversible ___
reversible and irreversible ___
irreversible ___
creaming (redistributed upon shaking)
flocculation
breaking
29
theories of emulsification mechanism of action of emulsifier
surface tension theory
oriented-wedge theory
plastic or interfacial film theory
30
surface tension theory
liquid's surface tension
emulsifiers facilitate breaking up large globules
31
liquids have ___ minimal surface area
minimal
32
if drops of the same liquid come into contact
they join
33
new larger drop has a smaller surface area than
total surface area of small drops
34
Emulsifying agents work by...
Reducing interfacial tension
reduce repellent force between two immiscible liquids
diminish each liquid's attraction for its own molecules
35
interfacial force
force resisting breaking up liquids into smaller molecules
36
oriented-wedge theory
molecular layer of emulsifying agent is curved around a droplet of internal phase
molecules of an emulsifier orient themselves into each phase
hint: think of surfactants
37
true or false: all emulsifiers have hydrophilic and hydrophobic parts
true
38
plastic or interfacial film theory
emulsifier surrounds the droplets of internal phase as thin layer of film
39
film prevents
contact and join of internal phase
40
emulsification is a two-step process
1. lowering interfacial force
2. formation of protective wedge film around droplet (stability)
41
maintaining stability of emulsions prevents
coalescence of droplets
42
emulsifying agent with relatively strong hydrophilic groups produces
O/W emulsion
43
emulsifying agent with relatively strong hydrophobic groups produces
W/O emulsion
44
emulsifying agents must be
stable
nontoxic
compatible
effective concentration 2.5-5% v/w
little odor, taste, color
do not affect therapeutics agents
45
emulsifiers can be
surfactants
stabilizers
thickeners
46
surfactants are classified as
anionic pH >8
cationic pH 3-7
nonionic pH 3-10
47
anionic surfactants
soaps (triethanomine oleate)
sulfonates (sodium laurel sulfate)
48
cationic surfactant
benzalkonium chloride (bacterial agent)
49
nonionic surfactants
sorbitans esters
polyoxyethylene derivatives
50
___ should be used in combination with ___
primary emulsifier
stabilizer (secondary emulsifier)
51
hydrophilic ointment USP
sodium laurel sulfate - primary emulsifier
acetyl alcohol - auxiliary emulsifier
52
stabilizers
high-molecular-weight alcohol
colloidal clays
53
high-molecular-weight alcohol
steryl alcohol
acetyl alcohol
cholesterol and derivatives (W/O emulsions)
54
colloidal clays
Mg hydroxide
Al hydroxide
bentonite
55
thickeners (viscosity)
carbohydrate materials (O/W)
proteins (O/W)
56
carbohydrates
ACACIA (compounding)
pectin
tragacanth
agar
microcrystalline cellulose
57
proteins
gelatin
egg yolk
casein
58
gelatin
too fluid emulsions which become more fluid upon standing
59
What is the HLB scale used for?
To classify surfactants based on their hydrophilic-lipophilic balance.
60
surfactants have HLB value
1 - 20
61
True or False: A higher HLB value indicates greater lipophilicity.
False. A higher HLB value indicates greater hydrophilicity.
62
What is the typical HLB range for O/W emulsifiers?
8-18.
63
What is the typical HLB range for W/O emulsifiers?
3-6.
64
emulsifiers should have HLB value similar to
external or internal phase
(stable emulsion)
65
two or more emulsifiers can be combined to
achieve proper HLB value
66
What are common methods for emulsion preparation?
Dry gum method (continental)
Wet gum method (English)
Bottle method (Forbes)
67
What is the dry gum method?
Oil, water, and gum are mixed in a 4:2:1 ratio
O/W emulsifier: acacia
emulsifier is triturated with oil in rough mortar (Wedgwood)
then add water
creamy white mixture
solid compounds (preservatives, stabilizers) are dissolved in water and added to primary emulsion
idk how to condense this my bad
68
dry method is used to make
mineral oil emulsion USP
69
What is the wet gum method?
method 4:2:1
gum (1 part) and water (2 parts) are mixed first, oil (4 pasts) is added after
trituration to emulsify oil and ensure uniformity
then add other ingredients
70
for both dry gum and wet gum methods at the end
transfer emulsion to graduate and bring to volume with water
71
Forbes bottle method
emulsions of volatile oil or oils with low viscosity
oil is added to acacia (powder) in dry bottle
shake and add water
shake again
72
in Forbes bottle method volume of water is
equal to volume of oil
added in portions
73
in Forbes bottle method primary emulsion should be diluted to
proper volume by water or aqueous solution of other ingredients
74
What are microemulsions?
stable transparent emulsions with very small droplet sizes
rapid and efficient absorption
both O/W and W/O
75
absorption of microemulsions
oral and transdermal
76
What is the function of preservatives in emulsions?
to prevent microbial growth and contamination
required by USP
77
preservatives for emulsions
benzoic acid/sodium benzoate or sorbic acid 0.2% (acidic pH)
methylparaben 0.2% + propylparaben 0.02%
78
stability of emulsions
physical
chemical
oxidation
79
__ is added to emulsions to prevent oxidation.
Antioxidants (chelating agents)
most oil undergo oxidation
80
chelating agents
organic compounds that form complexes with metal ions and inactive oxidation process
81
properties of antioxidants/chelators
compatible
do not affect therapeutic agents
soluble
stable anf effective
nontoxic
little odor, taste color
unreactive with containers
82
antioxidants for aqueous systems
ascorbic acid USP 0.05-3%
sodium bisulfate/metabisulfate 0.1%
sodium thiosulfate USP 0.02-1%
83
which antioxidants for aqueous systems might cause allergic reactions?
sodium bisulfate
metabisulfate
84
antioxidants for oil systems
ascorbic palmitate 0.01-0.2%
butylated hydroxytoluene 0.05-0.02
tocopherol 0.01-0.1%
sulfur dioxide 0.005-0.15%
85
chelating agents
eidetic acid/edetate disodium/calcium disodium edetate 0.1%
citric acid USP 0.3-2.0%
86
protect emulsions from
freezing
excessive heat
87
light-resistant containers for
light sensitive emulsions
88
addition of antioxidants
oxidative decomposition of emulsions
89
label warning
container must be tightly closed
90
internal (oral) emulsions should be stored in ___ while external ones at ___
refrigerator
room temperature
91
labeling
SHAKE WELL
92
lotion (emulsions)
calamine - antiseptic 5%
zinc oxide - antiseptic 5%
oxybenzone - sunscreen 6%
almond oil - part of emulsion vehicle system
acacia - emulsifying agent
rose water - part of emulsion vehicle system
93
oral emulsions
mineral oil emulsion
castor oil emulsion
simethicone emulsion
94
topical emulsion
estradiol emulsion
95
for oral emulsion use
spoonful
droperwise
96
avoid drug interactions
cholestyramine (oral suspension) and warfarin, oral diabetes drugs, tetracycline
aluminum hydroxide gel and antibiotics, digoxin
