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Dosage II > Liquid Dosage Forms: Emulsions > Flashcards

Liquid Dosage Forms: Emulsions Flashcards

1
Q

Emulsion

A

-system of 2 immiscible liquids
-one is dispersed as droplets -dispersed phase
-continuous phase

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2
Q

continuous phase of emulsion

A

-external phase
-determines touch, taste, smell of emulsion

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3
Q

Applications of emulsion

A

-oral
-external
-IV

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4
Q

oral emulsion

A

-O/W to mask taste of oil and enhance absorption of oil

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5
Q

External emulsion O/W

A

-water-washable
-vanishing cream

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6
Q

External emulsion W/O

A

-for cleansing skin
-cold cream

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7
Q

IV lipid emulsion

A

-O/W
-parenteral nutrition
-100mL of 20% lipid emulsion provides 200kcal, while 100 mL of 5% dextrose only provides 20kcal
-critical that droplet size is less than 1mcm to avoid embolisms in capillaries

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8
Q

Interfacial phenomena

A

-molecules attracted to each other equally in all directions except at boundary between phases
-imbalance of interaction forces leads to random movement of molecules from interface to bulk phase
=fewer molecules by area at the interface

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9
Q

water force of attraction

A

H bond

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10
Q

oil force of attraction

A

london dispersion forces

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11
Q

Interfacial tension

A

-interface resists expansion in response to attempt to reverse random movement of molecules
-force of tension per unit length of interface
-stronger force in bulk phase = higher interfacial tension
-larger tendency to interact = less interfacial tension
-high temp = lower tenstion (forces are reduced at high heat)

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12
Q

Emulsifiers

A

-stabilize emulsion

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13
Q

types of emulsifiers

A

-surfactants
-hydrophilic colloids (polymers)
-finely divided solid particles

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14
Q

Monomolecular film

A

surfactant

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15
Q

multimolecular film

A

hydrophilic colloid

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16
Q

solid particle film

A

fine partivles

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17
Q

Surfactants

A

-contain hydrophobic and hydrophilic regions
-orient ar interface and LOWER interfacial/surface tension
-acts as clamp to bind oil and water together

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18
Q

Surfactant classification

A

-anionic
-cationic
-zwitterionic
-nonionic

19
Q

Hydrophile-lipophile balance (HLB)

A

-measure relative concentration of hydrophilic and lipophilic regions of surfactant
-calcualted via formula

20
Q

HLB value for non-ionic surfactants

A

-ranges from 0-20

21
Q

low HLB indicates

A

greater lipid solubility

22
Q

How to get desired HLB

A

-mixture of emulsifying agents
-HLB = aX + (1-a)Y

-X=HLB of surfactant 1
-Y = HLB of surfactant 2
-a = fraction of surfactant 1 in surfactant mixture

23
Q

Rule of Bancroft

A

-relative solubility of surfactant determines type of emulsion
-i.e.the phase in which a surfactant is more soluble becomes the continuous phase

24
Q

Rule of Bancroft example

A

-a surfactant with a high HLB (>10, soluble in water) forms an o/w emulsion

25
Q

1 L of O/W emulsion contains 3g of Span 80 (HLB 4) and 7g of Tween 80
(HLB 15). What is the HLB value of the emulsion product?

A

idk

26
Q

Micelles

A

-hydrophobic core
-hydrophilic shell

26
Q

Micelle formation

A

-surfactant molecules aggregate as the concentration increases above CMC (critical micelle concentration)

27
Q

Center of micelle

A

-lipid-like region
-capable of dissolving water-insoluble drugs

28
Q

Hydrophillic colloids

A

-polymers
-used in O/w emulsions
-form multimolecular film at interface = increase viscosity of water
-does NOT lower interfacial tension - instead blocks particles from bumping into ea other

29
Q

hydrophilic colloid examples

A

-acacia
-tragacanth
-gelatin

30
Q

Finely Divided solid particles

A

-less than 1micron can absorb at interface
-form film of fine particles

31
Q

finely divided solid particle examples

A

-bentonite, mgAl silicate, Al hydroxide: hydrophilic (o/w)
-charcoal: hydroPHOBIC (w/o)

32
Q

Phase in which the emulsifier is most soluble

A

-external (continuous) phase

33
Q

W/O emulsion if

A

-HLB LESS than 10
-contact angle of solid particles is GREATER than 90 degrees

34
Q

O/W emulsion if

A

-HLB GREATER than 10
-HYDROPHILLIC COLLOIDS
-contact angle of particles is LESS than 90

35
Q

Hydrophilic emulsion

A

-O/W

36
Q

Hydrophobic emulsion

A

-W/O

37
Q

Instability of Emulsion

A
  1. Creaming
  2. Coalescence
  3. Phase Inversion
38
Q

Creaming

A

-Stokes Law
-reversible as long as. interfacial film maintains integrity of individual droplets
-low density starts floating
-shake before use

39
Q

Stokes law

A

kys

40
Q

Coalescence

A

-droplet size increase bc interfacial film unable to maintain individual droplets
-irreversible
-ultimately leads to layer of oil and layer of water (broken emulsion)
-cannot fix by shaking
-must be reformulated

41
Q

Phase Inversion

A

-due to phase volume ration exceeding 74% (it should be under 50%)
-O/W emulsion stabilized with sodium stearate can be inverted to W/O type using heard water (containing calcium)

42
Q

Conversion of Na Stearate to Ca stearate

A

-high HLB to low HLB
-O/W to W/O
-phase inversion by using hard water (containing calcium)

43
Q

matching

A

matching

Dosage II (20 decks)

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