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PHARM 124 Final; > Emulsions > Flashcards

Emulsions Flashcards

1
Q

What is an emulsion?

A

Dispersed system containing at least two immiscible liquids

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2
Q

What is the dilution test?

A

Determines emulsion type- relies on the fact that o/w emulsions can be diluted with water and w/o can be diluted with oil

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3
Q

What is the conductivity test?

A

An o/w emulsion will be a better conductor than a w/o one

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4
Q

What is the dye-solubility test?

A

Determines emulsion type- uses oil soluble and/or water soluble dyes.

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5
Q

What type of emulsion is used for IV administration?

A

O/W

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6
Q

What type of emulsion is used for oral administration?

A

O/W to ensure a pleasant taste

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7
Q

What type of emulsion is used for IM administration?

A

W/O

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8
Q

What additives are used for emulsions?

A

Antioxidants, preservatives, humectants

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9
Q

Which specific oils can be used for IV administration?

A

Cottonseed, soya bean oil. safflower oil

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10
Q

What types of anionic emulsifying agents are there?

A

Alkali metal and ammonium soaps (o/w)
Amine soaps (o/w)
Sulfated and sulfonated compounds (o/w)
Soaps of divalent and trivalent metals (w/o)

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11
Q

What types of non-ionic emulsifying agents are there?

A 
Polysorbates (o/w)
Fatty alcohol polyglycol ethers (o/w)
Fatty acid polyglycol esters (o/w)
Poloxalcohols (o/w)
Glycol and glycerol esters (w/o)
Sorbitan esters (w/o)
Higher fatty alcohols (emulsion type depends on other surfactant)
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12
Q

Which surfactants are soluble for parenteral injections?

A

Lecithin, polysorbate 80, poloxamers

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13
Q

What is an in situ emulsifier?

A

Emulsifier is formed upon mixing of separate components during the compounding process

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14
Q

What are quaternary ammonium compounds? When are they best used at?

A

Surfactants that form cations in aqueous solutions. Best at a pH of 4-6, and incompatible with anionic surfactants and polyvalent anions.

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15
Q

What are spans? HLB range?

A 
Sorbitan esters (w/o emulsions)-- hydroxyl groups of sorbitan esterified with acids.
HLB range 2-10
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16
Q

What are tweens? HLB range?

A

Polysorbates (o/w)– polyethylene glycol derivatives of sorbitan esters.
HLB range 10-18

17
Q

What are the advantages of tweens (polysorbates) as surfactants?

A

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

18
Q

What’s an example of a semisynthetic polysaccharide?

A

Methylcellulose (o/w)

19
Q

What is the relationship between surfactant concentration and interfacial tension?

A

More surfactant=less interfacial tension, up to a point which we call the CMC of the surfactant. At the CMC (surface layer is saturated with surfactant), micelles start to form, which don’t affect interfacial tension.

20
Q

What equation can we use to describe the interfacial tension and adsorption of surfactant molecules? What is surface excess surfactant concentration?

A

Gibb’s adsorption equation. Represents surface excess surfactant concentration, which is the portion of surfactant that occupies that interface and contributes to lowering the interfacial tension.

21
Q

What is a mixed micelle?

A

Blend of surfactants used in the preparation of an emulsion

22
Q

What is the aggregation number?

A

Number of surfactant molecules that form one micelle

23
Q

What does HLB describe?

A

Describes the hydrophilic-hydrophobic characteristics. 0-10 means it’s lipophilic. 10-20 represents hydrophilic characteristics.

24
Q

Which emulsifying agents form monomolecular films around the disperse phase?

A

Ionic and non-ionic surfactants

25
Q

Which emulsifying agents form multimolecular film around the disperse phase?

A

Hydrocolloids- acacia, gelatin

26
Q

How does bentonite exert its emulsifying properties?

A

Forms a solid particle film on the surface of oil droplets

27
Q

Describe the properties of non-ionic and ionic emulsifiers

A

Non-ionic: less toxic, less irritant. Includes those that can be used for parenteral administration
Ionic: should not be given orally, irritates the GIT. Cationic are toxic at low concentrations and should only be used externally, while anionic have a high pH and are unsuitable for broken skin.

28
Q

What is the role of antioxidants?

A

Prevents it from going rancid by preventing auto-oxidation of oil and lipid components

29
Q

What is the role of preservatives?

A

Prevents growth of micro-organisms

30
Q

How are preservatives inactivated in emulsions?

A

Micellar binding of preservatives with surfactants may inactivate them

31
Q

What equipment can be used for emulsification?

A

Mechanical stirrers (allow for mixing of large quantities, used for low viscosity preparations)
Homogenizers (pressure through a small hole, not suitable for viscosities over 2000cP)
Ultrasonifiers
Colloid mills (frequently used)

32
Q

What is coalescence?

A

Complete fusion of droplets within an emulsion. Leads to a decrease in the number of droplets and irreversible separation of the two immiscible phases.

33
Q

How can you determine the rate of creaming/sedimentation in an emulsion?

A

Stoke’s law of sedimentation can be used. Creaming will result in a negative number.

34
Q

What stress conditions are used for assessing emulsion shelf life?

A

Aging and temperature
Centrifugation
Agitation

35
Q

What is the reason for coalescence and how can you prevent it?

A

Can be caused by a low zeta potential, high surface free energy, or high interfacial tension.
Can be prevented by adding protective colloids, adding more surfactant, or optimizing particle size.

36
Q

What is the reason for creaming and how can you prevent it?

A

Can be caused by flocculation and upward sedimentation.

Can be prevented by adding protective colloids or more surfactant.

37
Q

What is the reason for foaming and how can you prevent it?

A

Caused by too much surfactant in the formulation.

Can be prevented by reducing surfactant concentration.

38
Q

What is the reason for microbial growth in an otherwise preserved emulsion and how can you prevent it?

A

Can be caused by the preservative-surfactant interaction leading to reduced antimicrobial function.
Can be prevented by adding more, or a different preservative.

39
Q

What is the reason for unpleasant taste, and how can you prevent it?

A

Can be caused by an inappropriate amount of certain excipients, preservatives, or lack/inappropriate amount of sweetener and flavouring agent.
Can be prevented by reducing/optimizing excipient concentrations or adding more/different sweetener/flavour.

PHARM 124 Final; (5 decks)

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