4. Disperse systems

Question 0

What is a suspension?

Answer 0

solid in a liquid

Question 1

What makes up a dispersion?

Answer 1

• a dispersed phase

- a continuous/dispersing phase

Question 2

What is an emulsion?

Answer 2

liquid in a liquid

Question 3

What is an aerosol?

Answer 3

solid or liquid in air

Question 4

What is a coarse dispersion?

Answer 4

• solute not dissolved and is visible
• suspensions
• emulsions

Question 5

What is a fine dispersion?

Answer 5

• solute not completely dissolved

- magmas and gels

Question 6

what are colloidal dispersions?

Answer 6

• solute not completely dissolved BUT not visible

- will scatter light

Question 7

What are molecular solutions?

Answer 7

• solute completely dissolved in solvent

- true solutions won’t scatter light

Question 8

Why are disperse systems thermodynamically unstable systems?

Answer 8

• larger particles have a greater tendency to separate from the dispersing phase
• solids settle, liquids rise to top
• must restore uniform distribution while moderate agitation for proper dosing

Question 9

What are the advantages of suspensions?

Answer 9

• ease of swallowing
• flexibility of dose
• bad tastes can be masked
• drug may have increased stability

Question 10

What are the disadvantages to suspensions?

Answer 10

• physically unstable, will separate over time
• if you don’t shake, dosing will be wrong
• pt may not like mouth-feel (esp. if particle size if large)

Question 11

What are the desirable attributes of a suspension?

Answer 11

• should settle slowly and be re-dispersed with gentle shaking
• particle size should remain fairly constant with shelf life
• should pour readily and evenly

Question 12

What are the parameters of sedimentation rate?

Answer 12

• it’s a function of particle size
• inverse function of viscosity (more viscous = slower settling)
• small particle sizes can cake or agglomerate (stick together)
• floccules can prevent caking

Question 13

What are floccules?

Answer 13

a loose aggregation of particles

Question 14

Why are floccules good?

Answer 14

• they form higher sediment volumes than non-flocculated suspensions
• loose structure = easy to re-disperse

Question 15

How can you form floccules in suspension?

Answer 15

by adding surfactant or sometimes electrolytes

• at specific concentrations they may neutralize surface charges

Question 16

Why should a viscosity increasing agent be adding to suspensions with floccules?
What kind of viscosity agent should be used?

Answer 16

• since the particles size is bigger (floccules), you need a higher viscosity to reduce settling

Want an agent that is:

• higher viscosity at low shear rates (storage, after shaking, pouring)
• low viscosity at high shear rates (shaking)

Question 17

Infants and neonates should have minimal exposure to:

Answer 17

• preservatives
• alcohol
• propylene glycol

Question 18

What is the expiration date for aqueous extemporaneous solutions?

Answer 18

14 days in the refrigerator

• to prevent microbial growth and increase stability
• need to add preservatives if need for longer than 14 days

Question 19

What are the constituents of suspensions or structured vehicles?

Answer 19

• active ingredient
• wetting agent
• suspending agent
• flocculating agent
• protective colloid
• sweetener
• preservative
• buffer system
• color agent
• flavor agent
• antifoaming agent

Question 20

What type of emulsion is more occlusive?

Answer 20

w/o

Question 21

What type of emulsion has better drug release?

Answer 21

o/w

Question 22

What is creaming?

Answer 22

In emulsions, when internal-phase droplets:

• rise to the top (o/w)
• sink to bottom (w/o)

Question 23

How can you stabilize an emulsion?

Answer 23

• surfactants
• hydrocolloids
• solid particles

Question 24

What do surfactants do?

Answer 24

- reduces repellent forces between phases - reduces attractive forces within each phase - breaks globules into smaller droplets Can be: anionic - sodium docusate, sodium oleate non-ionin - spans and tweens cationic - halides

Question 25

What do hydrocolloids stabilize emulsions?

Answer 25

- provide protective multi-molecule layers around dispersed droplets - provide charge, droplets repel each other - may swell to increase viscosity

Question 26

How do solid particles stabilize an emulsion?

Answer 26

- form layer around droplet and swell | - this increases viscosity and reduces attraction

Question 27

What is HLB? | What is it used for?

Answer 27

Hydrophilic-lipophilic balance System designed to aid in determining the amount and type of emulsifier needed to produce stable emulsions

Question 28

What are the 3 methods of extemporaneous compounding?

Answer 28

- continental - english - beaker - bottle

Question 29

What is the continental method?

Answer 29

- primary emulsion of oil, water and emulsifier (4:2:1) - acacia used as gum emulsifier - gum and oil mixed, then all of water added with vigorous trituration

Question 30

What is the english method?

Answer 30

- 4:2:1 - gum mixed with water to make mucilage - oil added in parts with vigorous mixing

Question 31

What is the bottle method?

Answer 31

- works best with low viscosity oil - 4:2:1 - gum and oil added to bottle - mix vigorously - then water, mix vigorously - make an in situ soap

Question 32

What is the beaker method?

Answer 32

- only 5% of synthetic emulsifier is needed - water soluble materials dissolved in water - oil soluble materials dissolved in oil - both solutions heating to 70 in water baths - internal phase added to external phase and mix until cooled to room temp

Question 33

Describe hydrophilic colloidal dispersions.

Answer 33

- like water, hydrate and swell to increase viscosity - may carry a charge, the charge keeps particles separated - quite stable with affinity between particles and continuous phase

Question 34

Describe hydrophobic colloidal dispersions.

Answer 34

- less stable than hydrophilic (no interaction between colloid and continuous phase) - stabilize by developing attraction between colloid particles and continuous phase - can carry a charge, repulsive forces and brownian motion keeps colloids dispersed - addition of electrolyte may neutralize charge and cause settling

Question 35

What is a two-phase gel?

Answer 35

gel made with discrete particles

Question 36

What is a single-phase gel?

Answer 36

if large organic macromolecules are uniformly distributed with no apparent boundaries between the dispersed and continuous phase

Question 37

What type of auxillary label should be used on disperse systems?

Answer 37

- shake well - refrigerate (if applicable) - external (if applicable)

Question 38

Why are disperse systems packaged in oversized containers?

Answer 38

- to facilitate shaking

Question 39

What is the usual concentration of surfactants in disperse systems?

Answer 39

2-5% ex. tween 80, span 20

Question 40

What will happen to a disperse system if a preservative is not used?

Answer 40

- will only last 2 weeks with refrigeration

Question 41

What is the ingredient function of: - hydrochlorothiazide - methycellulose - citric acid - sodium benzoate - aspartame - orange flavor - purified water

Answer 41

- API - suspending agent - pH adjuster - preservative - sweetener - flavor - vehicle