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OU Pharmaceutics > Exam 4 > Flashcards

Exam 4 Flashcards

1
Q

What is the particle size for molecular dispersions?

A

< 0.001 µm

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2
Q

What is the particle size for colloidal systems?

A

0.001 – 0.5 µm

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3
Q

What is the particle size for coarse disperions?

A

10 – 50 µm

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4
Q

What are two types of coarse dispersions?

A

suspensions, emulsions

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5
Q

What is a pharmaceutical suspension?

A

coarse dispersion in which insoluble solid particles are dispersed in a liquid dispersion medium

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6
Q

What should the particle size of suspensions be?

A

> 0.1 µm

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7
Q

What are the different types of administration for suspensions?

A

oral, topical, transmucosal, parenteral

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8
Q

T/F The stokes law is only applicable to dilute suspensions.

A

True

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9
Q

What is the concentration for “dilute suspensions”?

A

< 2 % solid

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10
Q

What is a promoting factor?

A

a factor that if it is increased then settling will increase

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11
Q

What are examples of promoting factors?

A

density, particle diameter, gravity

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12
Q

What is the force of attraction?

A

London-van der Waals type (VA)

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13
Q

What is the force of repulsion?

A

Electrical double layer (VR)

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14
Q

What is the net potential energy of interaction?

A

VT = VA + VR

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15
Q

With respect to the DLVO theory, what does it mean when Pmax < Thermal energy of particle?

A

irreversible aggregation

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16
Q

With respect to the DLVO theory, what does it mean when Pmax > Thermal energy of particle?

A

the dispersion is stable

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17
Q

With respect to the DLVO theory, what does it mean when Smin < Thermal energy of particle?

A

loose reversible flocculation

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18
Q

How can you increase the height of Pmax?

A

increasing zeta potential

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19
Q

How can you decrease the depth of Smin?

A

adding electrolytes

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20
Q

With respect to the state of the suspension, what are you doing by increasing the height of Pmax / increasing depth of Smin?

A

making the suspension more stable

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21
Q

What are properties / characteristics of flocculated particles?

A

weakly bonded, settle rapidly, do not form cake, easily resuspended

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22
Q

What are properties / characteristics of deflocculated particles?

A

settle slowly, eventually form sediment, form cake, difficult to resuspend

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23
Q

What are the characteristics of sidmentation of a flocculated system?

A

there is a distinct boundary, flocs carry small particles down

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24
Q

What are the characteristics of sidmentation of a deflocculated system?

A

there is a turbid supernatant, sediment segregates according to particle size

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25
Q

What is an oral suspension?

A

aqueous preparations with the vehicle flavored and sweetened to suit the taste preferences of the intended patient

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26
Q

What are the desirable qualities of a pharmaceutical suspension?

A

Does not settle, no cake formation, high suspendability, able to pour easily, pharmaceutically elegant, dispersed particle size should not change

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27
Q

What are examples of structured vehicles?

A

Carboxymethylcellulose (CMC), Polyvinylpyrrolidine (PVP), Xanthan gum, Benotnite, Tragacanth gum

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28
Q

What are properties of structured vehicles?

A

they entrap particles in a deflocculated manner to prevent settling, pseudoplastic/plastic in nature, allows particles to become easily dispersed

29
Q

Does high sedimentation volume produce a more or less stable solution?

A

more stable

30
Q

What does surfactants do?

A

reduce surface tension on solid-liquid interphase; can provide charge on particle surface; decrease surface free energy

31
Q

Why is concentration of surfactant important in flocculation?

A

At low concentrations, they can be used as wetting and deflocculating agents

32
Q

How does polymers act in flocculation?

A

part of their chain is absorbed on the particle surface and the remaining part of the chain is projected into the dispersion medium

33
Q

What does hydrophilic polymers do?

A

they coat the particles which make them less prone to caking

34
Q

How can you get the best suspension preparation?

A

if you know how to use structured vehicles hand in hand with flocculation strategy

35
Q

_____ powders have low contact angles in water. _____ powders have large contact angles in water.

A

hydrophilic / hydrophobic

36
Q

How can wettability be improved?

A

using surfactants (otoxynol) and wetting agents (glycerin, PG)

37
Q

What can you use to make your formulation pharmaceutically elegant?

A

suspending agents, flocculating electrolytes, wetting agents, sweeteners, preservatives, flavoring agents, color

38
Q

What is a suspending agent?

A

something that entraps particle in a deflocculated manner

39
Q

How do you prepare suspensions?

A

wet the dispersed phase particles with wetting agent; dissolve soluble formulation ingredients in dispersion phase; add dispersion phase in portions to the wetted particles and mix thoroughly

40
Q

Why must suspensions be refrigerated?

A

high temperatures may increase solubility and low temp may increase crystallization

41
Q

How come neonatal suspensions don’t need flavoring?

A

neonates cannot taste or smell; also have underdeveloped kidney so you don’t want to add anything unnecessary

42
Q

Under which patient conditions should you not use alcohol in suspensions?

A

elderly patients with a history of depression, patients with liver problems

43
Q

What are the common categories of pharmaceutical suspensions?

A

antacid, antibacterial, rectal, dry powders for suspension

44
Q

What are characteristics of emulsions?

A

thermodynamically unstable system; consists of at least two immiscible liquid phases; stabilized by an emulsifying agent

45
Q

What are the types of emulsions?

A
  • Oil-in-water

- Water-in-oil

46
Q

What is an oil-in-water phase?

A

Nonpolar dispersed phase in polar dispersion medium; medicinal emulsions

47
Q

What is an water-in-oil phase?

A

Polar dispersed phase in nonpolar dispersion medium; externally applied emulsions

48
Q

How do you test whether an emulsion is oil-in-water or water-in-oil?

A
  • Dye method (Methylene blue dusting; M.blue dissolves easily in water)
  • Dilution of dispersion medium
  • Electrical circuit method (electrical current will form in water)
49
Q

What prevents coalescence?

A

the emulsifying agent

50
Q

What is coalescence?

A

process by which two or more droplets, bubbles or particles merge during contact to form a single daughter droplet, bubble or particle

51
Q

What is the surface tension theory?

A

the reduction in interfacial tension prevents coalescence

52
Q

What is the oriented wedge theory?

A

the monomolecular film around the droplets prevents coalescence

53
Q

What is the interfacial film theory?

A

the particulate film around the droplets prevents coalescence

54
Q

What type of emulsifier is Sorbitan monooleate (Span 80)?

A

Nonionic surfactant

55
Q

What type of emulsifier is Acacia?

A

Hydrophilic colloid

56
Q

What type of emulsifier is Veegum (Mg-Al-silicate)?

A

Solid particle

57
Q

What are characterstics of hydrophilic colloids as an emulsifier?

A

Form multimolecular film at the interface; strong film resists coalescence; effect is the increased viscosity; usually promote oil-in-water emulsions

58
Q

What are characteristics of creaming?

A
  • Negative sedimentation where ρDispersed < ρDispersion
  • Gravity-assisted sedimentation where ρDispersed > ρDispersion
  • is reversible
59
Q

How can you prevent the breaking of emulsions?

A
  • have uniform particle size
  • have optimal viscosity
  • have phase volume of 50/50 but critical point is 74% oil in oil-in-water emulsion
  • increase the zeta potential
60
Q

What can heparin do in an oil-in-water emulsion?

A

it has to be an oil-in-water emulsion that has been stabilized by lecithin; it undergoes charge reversal; heparin flocculates charge-reversed emulsion by bridging the droplets and destabilizes the droplets

61
Q

What is phase inversion?

A

when the dispersion medium becomes dispersed phase and dispersed phase becomes dispersion medium

62
Q

What are the ways in which you can have a phase inversion?

A
  • O/W Emulsion + Oil -> W/O Emulsion
  • W/O Emulsion + Water -> O/W Emulsion
  • Addition of salt: O/W emulsion stabilized with Na stearate inverts to W/O emulsion upon addition of CaCl2
63
Q

T/F Emulsions do not have an effect on what the dispersion medium is.

A

F. Whatever the emulsifying agent love, it will make that the dispersion medium

64
Q

What is Bancroft’s rule?

A

The phase in which the emulsifying agent is more soluble will be the external phase

65
Q

What does HLB stand for?

A

hydrophilic lipophilic balance

66
Q

Describe the values of the HLB system.

A

Can go up to 40; useful medicinal range is 1-20; the higher the number, the more hydrophilic

67
Q

T/F: A single emulsifying agent is more effective than a mixture of emulsifying agents.

A

False: A mixture of emulsifying agents is more effective than a single agent

68
Q

How is calcium soap formed within an emulsion?

A

via a reaction between oleic acid and Ca(OH)2

OU Pharmaceutics (9 decks)

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