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PHARM 124 Final > Emulsions > Flashcards

Emulsions Flashcards

1
Q

Which type of emulsions are developed to produce a sustained release of API

A

Multiple emulsions

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2
Q

What is a microemulsion?

A

Dispersed globules are of colloidal dimensions (1nm-1 microm)
Usually transparent

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3
Q

What are nanoemulsions?

A
  • They are of colloidal nano dimensions (less than 200nm
  • usually transparent
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4
Q

Explain the 3 types of tests for identifying emulsion types

A
  1. Diultion test
    - o/w can be diulted with water
    - w/o can be diluted with oil
  2. Conductivity test
    - conductivity of water as a continuous/external phase is much more efficient than oil as the external phase
  3. Dye-solubility test
    - oil-soluble and water-soluble dyes can be used to determine the type of emulsion formed
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5
Q

What type of emulsions are usually for oil administration

A

Mostly o/w to ensure a pleasant taste

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6
Q

What type of emulsions are used for INTRAVENOUS administration

A

must be oil/water

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7
Q

What type of emulsions are used for INTRAMUSCULAR administration

A

water/oil for sustained release

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8
Q

What emulsions are used for external administration if you want:
- no grease
- water-washable

A

water/oil

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9
Q

What emulsions are used for external administration if you want:
- grease
- occlusive
- water repellent film

A

water in oil

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10
Q

What additives are used for emulsions? (3)

A

Antioxidants
Preservatives
Humectants

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11
Q

Which oils are used for oral administration (4)

A
  • liquid paraffin
  • Caster oil
  • Cod liver oil
  • Peanut oil
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12
Q

Which oils are used for intravenous administration? (3)

A
  • cottonseed oil
  • soya bean oil
  • safflower oil
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13
Q

Which oils are used for external administration? (3)

A
  • turpentine oil
  • benzyl-benzoate
  • various oils
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14
Q

What are the desirable properties of non-ionic emulsifiers

Which type of emulsifying agent should NOT be given orally?

Which type of emulsifying agents can suitable for parenteral injections?

A

non-ionic emulsifiers
- less toxic, less irritant

Ionic emulsifiers

Only some non-ionic surfactants (lecithin, polysorbate (tween 80), poloaxamers

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15
Q

Explain the type of charge that synthetic and semi-synthetic anionic surfactants

A
  • Hydrophilic head is negative
  • orient in aqueous environment & form micelles
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16
Q

What are types of anionic surfactants and their emulsion type.

A

Only soaps of divalent and trivalent metals form water/oil (calcium oleate) (in situ)

  • alkali metal and ammonium soaps (sodium stearate) (in situ)
  • amine soaps (triethanolamine stearate)
  • sulfated compounds (sodium lauryl sulfate)
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17
Q

Explain Cationic surfactants and what type of surfactant agent they are and their emulsion type

A
  • Hydrophilic head is positive
  • quaternary ammonium compounds (o/w)
18
Q

What are some examples of non-ionic surfactants? what are their emulsion types?

A
  • Polysorbate tweens (o/w)
  • Fatty polyglycol ethylenes (o/w)
  • Glycerol esters (w/o)
  • Sorbiton esters span (w/o)
19
Q

What are examples of naturally occuring emulsifying agents? determine their emulsion type

A

Polysaccharides acacia o/w
methylcellulose o/w

Sterols (cholesterols) w/o

20
Q

What are some examples of Antioxidants additives? what are they used for

A

To prevent rancidity and auto-oxidation

BHA, BHT (butyls)

21
Q

What are some examples of preservatives?

A

Cationic surfactants

  • quarternary ammonium compouds
  • benzoic acid, parabens
22
Q

What is the role of humectants and give examples

A

Reduce evaporation of the water phase to prevent drying (absorbs water from air)

Examples:
- propylene glycol
- glycerol
- sorbitol

23
Q

What are the advantages of polysorbates as surfactants?

A

-Versatile
-can be used in all dosage forms
- safe
- non-toxic
- non-irritating

24
Q

What is the relationship between surfactant concentration and interfacial tension?
How do they orient themselves?

A

As we increase surfactants, the interfacial tension decreases up until CMC (micelle formation, then stays constant)

oil/water interface

25
Q

What is the effect of micellization on interfacial tension?

A

No effect after CMC

26
Q

Contrast between non-ionic and ionic surfactants in micelles formation

A

non-ionic surfactants form micelles at lower concentrations than ionic surfactants
- ionic surfactants cause repulsion

27
Q

Contrast between a surfactant with a high CMC and low CMC level.

A

A surfactant with a high CMC level is more efficient as it will have a lot of monomers that can reduce interfacial tension (more stable for emulsions)

28
Q

What are some micelle characteristics?

Contrast between a micelle in water and in oil.

A

Characteristics:
- diameter is 2x length of surfactant
- colloidal dimensions (1nm-microm)
- Association colloids

Micelle in water
- hydrophilic heads face outside

Micelle in oil (inverted micelle)
- hydrophilic heads face inside

29
Q

What is the HLB number and type of emulsion it forms for hydrophobic and hydrophilic surfactants?

A

0-10 hydrophobic w/o

10-20 hydrophilic o/w

30
Q

What emulsifying agents form the following films:

Monomolecular film
Multimolecular film
Solild particle film

A

Monomolecular film
- ionic and non ionic surfactants

Multimolecular film
- hydrocolloids (polymers, acacia, gelatin)

Solild particle film
- Bentonite, Mg-hydroxide

31
Q

What is phase inversion and how can it be utilized?

A

Change of emulsion type from w/o to o/w

  • The water phase is poured into oil phase
32
Q

What are the equipments used for emulsification? (4)

A

Mechanical stirrers
- used for low viscosity preparations
- large quantities may be mixed

Homogenizers
- not suitable for viscosity

Ultrasonifiers
- produces a uniform emulsion
- gentle –> powerful

Colloid Mills
- frequently used

33
Q

What are the 3 primary phenomena for physical INSTABILITY of emulsions.
Explain them.

A
  1. creaming or sedimentation
    - Caused my flocculation of droplets moving upward (creamation) and downward (sedimentation) within the continuous face
    - undesirable as the emulsified product must remain homogenous to deliver correct/uniform dose
    - Reversible
  2. Flocculation
    - loose clusters (attractive forces dominate)
    - increases the rate of creaming
    - Reversible
  3. Coalescense (breaking, cracking)
    - Complete fusion of droplets which leads to a ↓ # of droplets
    - Separation of 2 immiscible phases
    - Irreversible
34
Q

How would you determine the rate of creaming or rate of sedimentation in an emulsion?

A

Stokes law:
Sedimentation: +ve rate
Creaming: -ve rate

35
Q

What kind of “stress conditions” are used for assessing emulsion shelf-life? (3)

A
  1. Aging and temperature increase
  2. Centrifugation (to accelerate separation into two layers)
  3. Agitation (to reflect conditions of shipping)
36
Q

How do you reduce the rate of creaming/sedimention in an emulsion?

A
  • ↓ droplet size
  • ↓ density difference between 2 phases (not used in practice)
  • Increase viscosity of continious phase (hydrocolloids)
  • control of the disperse phase conc.
37
Q

What is the reason for coalescence?
How to prevent?

A

Caused by:
- low zeta potential
- high surface free energy
- High interfacial tension

Prevent:
- Add protective colloids
- Optimize particle size
- Add more surfactant

38
Q

What is the reason for foaming and what steps would you take to prevent foaming in an
emulsion?

A

Too much surfactant in formulation

  • reduce
39
Q

What are examples of In situ Soap formation? (3)

A
  • Calcium oleate
  • Triethanolamine stearate
  • Sodium stearate
40
Q

Differentiate between the dry gum and wet gum method

A

Dry gum
- Calculated amount of Acacia is triturated with oil
- 4 parts oil + 1 part gum

Wet gum
- Acacia starts off in mortar & water is added
- 2 parts water + 1 part gum

PHARM 124 Final (3 decks)

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