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PHRM 1300 - Final > Section 4: Disperse Systems > Flashcards

Section 4: Disperse Systems Flashcards

1
Q

In a disperse system, what is the dispersed substance known as?

A

Dispersed phase

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2
Q

In a disperse system, what is the vehicle known as?

A

Continuous or dispersing phase

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3
Q

What is a solid in a liquid called?

A

A suspension

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4
Q

What is a liquid in a liquid called?

A

An emulsion

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5
Q

What is a solid/liquid in air called?

A

An aerosol

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6
Q

What does suspension mean by USP terms?

A

Dosage forms that are solid-liquid dispersions

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7
Q

What are 4 other names for suspensions?

A

1) Milk
2) Magma
3) Lotion
4) Syrup

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8
Q

What is an example of a suspension that is called a “milk”?

A

Milk of magnesia

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9
Q

What is an example of a suspension that is called a “magma”?

A

Bentonite magma

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10
Q

What is an example of a suspension that is called a “lotion”?

A

Hydrocortisone lotion

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11
Q

What is an example of a suspension that is called a “syrup”?

A

Doxycycline syrup

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12
Q

What are the USP guidelines for nomenclature of dosage forms?

A

Be named by route of administration (ex: oral, topical) and their physical system (ex: tablet, solution)

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13
Q

What is an example of an old name that was changed to meet the requirements of USP nomenclature?

A

White lotion is now called zinc sulfide topical suspension USP

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14
Q

What can define a dispersed system?

A

Particle size

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15
Q

What are 2 characteristics of coarse dispersions?

A

1) Solute not dissolved completely and is visible

2) Size over 10 micrometers

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16
Q

What are coarse dispersions generally used for?

A

Suspensions and emulsions

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17
Q

What are 2 characteristics of fine dispersions?

A

1) Solute not completely dissolved

2) Size between 0.5 and 10 micrometers

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18
Q

What are fine dispersions generally used for?

A

Magmas and gels

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19
Q

What are 2 characteristics of colloidal dispersions?

A

1) Solute not completely dissolved, but not visible

2) Size between 1 nanometer and 0.5 micrometers

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20
Q

What is a property of colloidal dispersions?

A

Will scatter light

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21
Q

What are 2 characteristics of molecular solutions?

A

1) Solute completely dissolved in solvent

2) Size below 1 nanometer

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22
Q

Do true molecular solutions scatter light?

A

No

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23
Q

Disperse systems are thermodynamically ______

A

Unstable

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24
Q

True or false: disperse systems are 1-phase systems

A

False, they are 2-phase systems

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25
Q

What does a larger particle size cause with respect to dispersion?

A

Larger particle = greater tendency to separate from the dispersing phase

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26
Q

____ tend to settle while _____ rise to the top

A

Solids; liquids

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27
Q

What is needed for dosing accuracy with disperse systems?

A

The dispersed phrase should be restored to uniform distribution throughout the dispersing phase with moderate agitation of the container

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28
Q

What are suspensions?

A

Two-phase systems of a finely divided solid uniformly dispersed in a liquid phase

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29
Q

What is the normal particle size for suspensions?

A

10-50 micrometers

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30
Q

For suspensions, what is the continuous phase usually?

A

Aqueous

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31
Q

For suspensions, how much solubility does the solute have in the continuous phase?

A

Minimal

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32
Q

What is often done to suspensions for oral use?

A

Sweetened or flavoured

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33
Q

What are suspensions for topical use called?

A

Lotions

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34
Q

What are 4 advantages to suspensions as a dosage form?

A

1) Easy to swallow
2) Flexibility in giving doses of different sizes
3) Able to mask disagreeable tastes
4) Drug may have increased stability

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35
Q

What are 3 disadvantages to suspensions as a dosage form?

A

1) Physically unstable and will separate over time
2) Dosing inaccuracy if homogeneity not restored before use
3) May have an unpleasant feeling in the mouth, especially if large particle size

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36
Q

What are 3 desirable attributes of a suspension?

A

1) Should settle slowly and be readily re-dispersed with gentle shaking
2) Particle size should remain fairly constant over the product’s shelf-life
3) Should pour evenly and readily

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37
Q

What is a disperse system?

A

A liquid preparation containing undissolved or immiscible drug distribution throughout the vehicle

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38
Q

What are the 6 factors involved in Stokes law?

A

1) Rate of settling
2) Diameter of particles
3) Density of particle
4) Density of medium
5) Gravitational constant
6) Viscosity of the medium

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39
Q

What does Stokes :aw explain?

A

Rate of settling in a suspension

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40
Q

What 3 things does Stokes Law indicate?

A

1) Sedimentation is a function of particle size
2) Sedimentation is an inverse function of viscosity
3) Rate of sedimentation can be slowed by reducing the particle size and/or increasing the viscosity of the medium

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41
Q

With respect to Stokes Law, what does a small particle size mean?

A

Tendency for caking or agglomeration increases

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42
Q

What does agglomeration prevent?

A

Easy redispersion of settled particles

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43
Q

What is a way to prevent agglomeration?

A

Forming floccules

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44
Q

What are floccules?

A

A loose aggregation of particles

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45
Q

What holds floccules together?

A

Weak particle-particle bonds (van der Waals interactions)

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46
Q

What is a difference between flocculated and non-flocculated suspensions?

A

Flocculated suspensions form a higher sediment volume

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47
Q

What does the loose structure of flocculated suspensions allow for?

A

Easy redispersion

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48
Q

How can floccules be formed?

A

By adding a small quantity of surfactant (or sometimes electrolytes), which at specific concentrations may neutralize surface changes

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49
Q

What changes once floccules are formed?

A

Particle size becomes larger

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50
Q

What should be added because floccules have a larger particle size?

A

A viscosity-increasing agent

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51
Q

What does thixotropic mean?

A
  • When a substance can switch between solid and liquid

- Usually appears as solid when no pressure is applied, and behaves like a liquid when sufficient pressure is applied

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52
Q

What must be considered when turning a solid dose form into a liquid oral dose form?

A

Stability, bioavailability, preservative, flavour, and colour

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53
Q

What is the typical procedure when turning a solid dose form into a liquid oral dose form?

A
  • Powder/empty the appropriate number of tablets/capsules
  • Use a mortar and pestle and an appropriate levigating agent to prepare a smooth paste
  • Add structured suspending vehicle in portions
  • Make to volume, mix by inversion, and dispense into suitable bottle
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54
Q

What is an appropriate levigating agent when turning a solid dose form into a liquid oral dose form?

A

Glycerin

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55
Q

What is an appropriate vehicle when turning a solid dose form into a liquid oral dose form?

A
  • A commercially-prepared one like Ora-Sweet

- May also use syrup or a methylcellulose-type vehicle

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56
Q

What must be done when doing compounding for infants?

A

Minimize exposure to preservatives, alcohol, and propylene glycol

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57
Q

What is the go-to expiration for aqueous products as directed by the USP?

A

No more than 14 days in the fridge

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58
Q

When can an expiration date exceed 14 days?

A

With the use of preservatives

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59
Q

What is an emulsion?

A

A dispersion of small droplets of liquid in another immiscible liquid

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60
Q

What is the third phase of an emulsion?

A

Emulsifying agent

61
Q

What kind of emulsion involves the continuous phase being aqueous?

A

Oil and water emulsion

62
Q

What kind of emulsion involves the continuous phase being oleaginous?

A

Water and oil emulsion

63
Q

What can emulsions be used for?

A

Oral, topical, parenteral, or ophthalmic

64
Q

What are the most common emulsions?

A

Topical

65
Q

What are very uncommon emulsions?

A

Oral

66
Q

What is an advantage to water and oil emulsions?

A

More occlusive (air can’t get through it when applied topically)

67
Q

What is an advantage to oil and water emulsions?

A

Better drug release

68
Q

What is an example of a water in oil emulsion for topical use?

A

Vaseline

69
Q

What is a disadvantage to emulsions?

A

Physically unstable and will revert to 2 immiscible phases

70
Q

What type of emulsion will cause droplets to rise to the top?

A

Oil and water

71
Q

What type of emulsion will cause droplets to settle to the bottom?

A

Water and oil

72
Q

**What can be done after creaming has occurred?

A

Re-disperse with shaking

73
Q

**What is creaming?

A

When internal phase droplets merge and rise to top or settle to bottom

74
Q

How can emulsions be stabilized?

A

Use of surfactants, hydrocolloids, or solid particles

75
Q

What is a surfactant?

A

Hydrophilic or lipophilic portions of molecule that concentrate at oil:water interface

76
Q

What do surfactants do?

A

Lower interfacial tension between phases which reduces repellant forces between them, and reduces attractive force within each phase

77
Q

What does a surfactant facilitate?

A

Breaking of globules into smaller droplets

78
Q

What are the 2 types of surfactants and what are 2 examples of each?

A

1) Anionic (sodium docusate, sodium oleate)

2) Non-ionic (Spans, Tweens)

79
Q

What type of surfactants are rarely used and why?

A

Cationic because irritation and toxicity occurs in the amount required

80
Q

What do hydrocolloids provide?

A
  • Protective multi-molecule layers around dispersed droplets

- May provide a charge which causes droplets to repel each other

81
Q

What are the 3 types of hydrocolloids and what is an example of each?

A

1) Natural (gelatin)
2) Semi-synthetic (methylcellulose)
3) Synthetic (carbopols)

82
Q

What happens to solid particles when mixed with droplets and what does this cause?

A
  • Tend to form layer around droplet and swell

- Increases viscosity and reduces attraction between droplets

83
Q

What is the function of auxiliary agents?

A

Thicken

84
Q

What are examples of auxiliary agents?

A
  • Fatty acids
  • Fatty alcohols
  • Fatty esters
85
Q

What is the hydrophilic-lipophilic balance?

A

A system designed to aid in determining type and amount of emulsifier needed to prepare stable emulsions

86
Q

How are HLB values determined?

A

Experimentally

87
Q

What is the scale for HLB values?

A

1-18

88
Q

What does a low HLB value indicate?

A

Emulsifier is oil-soluble, so oil phase will predominate and a water and oil emulsion will form

89
Q

What are HLB values assigned to?

A

Oils and oil-like materials

90
Q

What is the equation for the HLB value of an emulsion?

A

(quantity surfactant 1)(HLB surfactant 1) + (quantity surfactant 2)(HLB surfactant 2) / (quantity surfactant 1 + quantity surfactant 2)

91
Q

How are emulsions prepared in industry?

A

With large tanks and high-speed homogenizers or colloid mills

92
Q

What must be put into the system to make an emulsion?

A

Energy

93
Q

What are the 4 general methods for extemporaneous preparation of emulsions?

A

1) Continental
2) English
3) Bottle
4) Beaker

94
Q

What is used in the continental method of preparing emulsions?

A

4 parts oil, 2 parts water, and 1 par emulsifier/gum

95
Q

What is generally used as the gum in the continental method of preparing emulsions?

A

Acacia

96
Q

What type of mortar and pestle is generally used in the continental method of preparing emulsions?

A

Porcelain

97
Q

Describe the continental method of preparing an emulsion

A
  • Acacia is levigated with the oil until they are thoroughly mixed
  • Water is then added at once with vigorous trituration
  • Additional solid materials are dissolved in some of the remaining water (if they are water soluble); oil-soluble material is dissolved in oil
  • Preparation is transferred to a measuring cylinder and made to volume
98
Q

What is the same and different between the english and continental methods of preparing emulsions?

A
  • Same proportion of materials

- Different order of mixing

99
Q

Describe the english method of preparing an emulsion

A
  • Gum is triturated with water to make a mucilage

- Oil is added in portions with vigorous mixing

100
Q

When would the bottle method for making an emulsion be used?

A

If oil has low viscosity

101
Q

What is a similarity between the bottle and continental methods of preparing emulsions?

A

Same proportions of materials

102
Q

Describe the bottle method of preparing an emulsion

A
  • Acacia put into bottle, oil added, and vigorously mixed

- Water is added and more vigorous mixing

103
Q

Describe the beaker method of preparing an emulsion

A
  • All water soluble materials are dissolved in water and all oil soluble materials are dissolved in oil using beakers
  • Both solutions heated to about 70 C in a water bath
  • Internal phase added to external phase with mixing
  • Stirred until cooled
104
Q

What does acacia contain?

A

Neutral sugars and acids

105
Q

What is the continuum of dispersions?

A

From true solutions to coarse suspensions and emulsions

106
Q

What is the stability of colloidal dispersions?

A

Relatively stable

107
Q

What can colloidal dispersions consist of?

A

Single large molecule of high MW

108
Q

What can colloidal dispersions appear as?

A

True solutions that scatter light

109
Q

How is dispersion maintained in colloidal dispersions?

A

Brownian movement

110
Q

What are colloidal dispersions effective at?

A

“Solubilizing” insoluble drugs

111
Q

What are the 2 types of colloidal dispersions?

A

1) Lyophilic

2) Lyophobic

112
Q

What does higher viscosity mean for colloidal dispersions?

A

Improved system stability because interaction between particles is reduced

113
Q

What can cause a hydrophilic colloid to carry a surface charge?

A
  • The pH of the system

- Chemical functional groups of colloid

114
Q

_____ keeps particles separated

A

Charge

115
Q

What can neutralizing or changing the charge of particles cause?

A

Can cause them to attract each other and grow

116
Q

Are hydrophilic systems stable or unstable and why?

A
  • Quite stable

- High affinity between particles and the continuous phase

117
Q

Why are hydrophobic systems less stable than hydrophilic systems?

A

Hydrophobic systems have no interaction between colloid and continuous phase

118
Q

What causes settling in hydrophobic colloids?

A
  • Attraction then association between colloid particle

- Addition of electrolyte that may neutralize the charge

119
Q

How can a hydrophobic colloid be stabilized?

A

By developing some attraction between particles and continuous phase with surfactants or protective colloids that can coat the particle

120
Q

What keeps a hydrophobic colloid dispersed?

A

Mutual repulsive forces and Brownian movement

121
Q

What are gels?

A

Hydrophilic colloidal systems with high degree of cross-linking or association

122
Q

Gels have high ____

A

Viscosity

123
Q

Gels have _____ phase movement

A

Continuous

124
Q

What is the normal concentration of a gelling agent?

A

0.5-2%

125
Q

What kind of preparation is a gel?

A

A semi-solid preparation of small inorganic or large organic molecules interpenetrated by liquid

126
Q

When would a gel be called a magma?

A

When particle size is large

127
Q

What is a gel made of?

A

Discrete particles

128
Q

A gel is ____-phase

A

Two

129
Q

When is a gel single phase?

A

If large organic macromolecules are uniformly distributed with no apparent boundaries between dispersed and continuous

130
Q

What is an example of a single phase gel?

A

Natural gums

131
Q

What are gels useful for?

A

Preparing oral, topical, nasal, ophthalmic, and vaginal dose forms

132
Q

What are the 4 types of classification systems for gels?

A

1) Inorganic
2) Organic
3) Hydrogels
4) Organogels

133
Q

Jellies are ____ and contain ____

A
  • Structurally conherent

- Water and a thickening agent

134
Q

What is a common problem in the preparation of gelling agents?

A

Wetting them

135
Q

What are 4 examples of gelling agents?

A

1) Alginic acid
2) Bentonite or Vee gum
3) Carbomer
4) Poloxamer

136
Q

What is carbomer compatible with?

A

Alcohol

137
Q

What are disperse systems useful for?

A

Topical, oral, ophthalmic, and parenteral dose forms

138
Q

What should be done before using disperse systems?

A

Shake them

139
Q

What must the caregiver understand when giving a disperse system?

A
  • Needs to be shaken
  • Route
  • Storage
140
Q

What is the function of methylcellulose?

A

Suspending agent

141
Q

What is the function of citric acid?

A

pH adjuster

142
Q

What is the function of sodium benzoate?

A

Preservative

143
Q

What is the function of aspartame?

A

Sweetener

144
Q

What is the function of orange flavour?

A

Flavouring agent

145
Q

What is the function of purified water?

A

Solvent

146
Q

What is the function of tween 80?

A

Non-ionic surfactant

147
Q

What is the function of span 20?

A

Non-ionic surfactant

148
Q

What is the function of cherry syrup?

A

Vehicle

PHRM 1300 - Final (6 decks)

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