Liquid Dosage Forms: Emulsions

Question 1

Emulsion

Answer 1

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

Question 2

continuous phase of emulsion

Answer 2

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

Question 3

Applications of emulsion

Answer 3

-oral
-external
-IV

Question 4

oral emulsion

Answer 4

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

Question 5

External emulsion O/W

Answer 5

-water-washable
-vanishing cream

Question 6

External emulsion W/O

Answer 6

-for cleansing skin
-cold cream

Question 7

IV lipid emulsion

Answer 7

-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

Question 8

Interfacial phenomena

Answer 8

-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

Question 9

water force of attraction

Answer 9

H bond

Question 10

oil force of attraction

Answer 10

london dispersion forces

Question 11

Interfacial tension

Answer 11

-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)

Question 12

Emulsifiers

Answer 12

-stabilize emulsion

Question 13

types of emulsifiers

Answer 13

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

Question 14

Monomolecular film

Answer 14

surfactant

Question 15

multimolecular film

Answer 15

hydrophilic colloid

Question 16

solid particle film

Answer 16

fine partivles

Question 17

Surfactants

Answer 17

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

Question 18

Surfactant classification

Answer 18

-anionic
-cationic
-zwitterionic
-nonionic

Question 19

Hydrophile-lipophile balance (HLB)

Answer 19

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

Question 20

HLB value for non-ionic surfactants

Answer 20

-ranges from 0-20

Question 21

low HLB indicates

Answer 21

greater lipid solubility

Question 22

How to get desired HLB

Answer 22

-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

Question 23

Rule of Bancroft

Answer 23

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

Question 24

Rule of Bancroft example

Answer 24

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

Question 25

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?

Answer 25

idk

Question 26

Micelles

Answer 26

-hydrophobic core -hydrophilic shell

Question 26

Micelle formation

Answer 26

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

Question 27

Center of micelle

Answer 27

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

Question 28

Hydrophillic colloids

Answer 28

-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

Question 29

hydrophilic colloid examples

Answer 29

-acacia -tragacanth -gelatin

Question 30

Finely Divided solid particles

Answer 30

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

Question 31

finely divided solid particle examples

Answer 31

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

Question 32

Phase in which the emulsifier is most soluble

Answer 32

-external (continuous) phase

Question 33

W/O emulsion if

Answer 33

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

Question 34

O/W emulsion if

Answer 34

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

Question 35

Hydrophilic emulsion

Answer 35

-O/W

Question 36

Hydrophobic emulsion

Answer 36

-W/O

Question 37

Instability of Emulsion

Answer 37

1. Creaming 2. Coalescence 3. Phase Inversion

Question 38

Creaming

Answer 38

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

Question 39

Stokes law

Answer 39

kys

Question 40

Coalescence

Answer 40

-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

Question 41

Phase Inversion

Answer 41

-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)

Question 42

Conversion of Na Stearate to Ca stearate

Answer 42

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

Question 43

matching

Answer 43

matching