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Dosage Forms 2 > Exam 1 Definitions/Learning Objectives > Flashcards

Exam 1 Definitions/Learning Objectives Flashcards

1
Q

What are 3 types of liquid dosage forms?

A

Solution
Emulsion
Suspension

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2
Q

What is the definition of a solution?

A

A homogeneous molecular dispersion

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3
Q

What is the definition of an emulsion?

A

System of 2 immiscible liquids where one is dispersed as droplets
Oil in water, water in oil

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4
Q

What is the definition of a suspension?

A

Solid in water or oil

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5
Q

What are 3 advantages of Solution dosage forms?

A

Homogeneous- No content uniformity issues
Good bioavailability
Easy to manufacture

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6
Q

What are the 6 components of a solution?

A 
Active ingredient
Solvent
Buffer
Preservative
Antioxidant- Chelating agent
Flavor/sweeteners
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7
Q

What is the definition of a buffer?

A

A solution of a weak acid and the salt of its conjugate base

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8
Q

What is the function of the weak acid component in a buffer?

A

It removes the added base (OH-)

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9
Q

What is the function of the salt component in the buffer?

A

It removes the added acid (H+)

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10
Q

What is the definition of buffering capacity?

A

The ability of buffer to resist a change in pH due to addition of acid or base

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11
Q

What does C stand for in the buffering capacity equation?

A 
C= Total buffer concentration
C = [HA] + {A-]
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12
Q

What are 4 common buffers?

A

Citric acid
acetic acid
glycine
phosphoric acid

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13
Q

What are 2 things to keep in mind when selecting a buffer?

A
  1. Use a pH that provides maximum drug stability

2. Minimize irritation by making pH equal to that of the body fluid

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14
Q

What are 3 things you can do to minimize irritation when the pH cannot be matched to the surrounding fluid?

A
  1. Minimize buffering capacity
  2. Reduce volume
  3. Administer slowly
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15
Q

What is the purpose of antimicrobial preservatives?

A
  1. Protects the patient from pathogens

2. Maintains the potency and stability of dosage forms

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16
Q

What is the mechanism behind antimicrobial preservatives?

A

Adsorb to the bacterial membrane and disrupt it- often lyse the bacteria or prevent proliforation

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17
Q

What are the properties of the bacterial membrane that preservatives use to bind?

A

The negatively charged surface membrane and the lipophilicity of the membrane allows for hydrophobic interactions

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18
Q

Which antimicrobial preservatives use the lipid solubility to bind?

A

Alcohols, acids, esters

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19
Q

Which antimicrobial preservatives use the electostatic interactions to bind?

A

Quaternary ammonium compounds

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20
Q

How much bacterial content is allowed in ampules- injectable solutions?

A

None, solution must be sterile

For single dose vials no preservative is needed

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21
Q

How much bacterial content is allowed in multiple dose vials?

A

None, must be sterile

May contain up to 10 doses, require preservatives

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22
Q

How much bacterial content is allowed in opthalmic solutions?

A

None, must be sterile

Must contain a preservative if packaged in a multiple dose container

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23
Q

How much bacterial content is allowed in oral liquids?

A

Less than 100 pathogens/1 mL

Need preservatives for multiple dose packages

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24
Q

How much bacterial content is allowed in oral solids?

A

Less likely to carry bacteria than liquid forms
Can be contaminated with salmonella
Check raw materials and make sure facility is clean

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25
Q

Characteristics of ideal preservatives?

A
  1. Effective in low concentrations against a wide variety of organisms
  2. Soluble in formulation
  3. Non toxic
  4. Stable
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26
Q

List 5 pharmaceutical preservatives?

A
  1. Alcohols
  2. Acids
  3. Parabens
  4. Quaternary Ammonium Compounds
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27
Q

Characteristics of ethanol as a preservative?

A

Requires a concentration of greater than 15 percent
oral products only
can be lost because it is so volatile

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28
Q

Characteristics of Benzyl Alcohol as a preservative?

A 
Local anethetic action
Burning taste- not used orally
Water soluable
Stable over wide pH range
Highly used in parenterals
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29
Q

Characteristics of acids as preservatives?

A

Only active in the unionized form - lipid soluable because they have more affinity for the microbial membrane

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30
Q

What products are Benzoic acid utilized in?

A

Oral products

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31
Q

What products are Sorbic acid utilized in?

A

Oral products (excellent for molds/yeast)

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32
Q

Characteristics of Parabens as preservatives?

A

Widely used orally
Lipophillic and less lipophillic varieties (depends on length of hydrocarbon R group)
low soluability
Can cause skin sensitization when used dermatologically

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33
Q

What factors effect the action of preservatives?

A 
pH (ionized vs. unionized acids)
Complex formation (can't be used when complexed)
Adsorption by solids
Chemical stability (shelf life)
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34
Q

How can oxidation be prevented?

A

Add excipients

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35
Q

What excipients can be used to prevent oxidation?

A

Vitamins, essential oils, fats, oils

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36
Q

What are the 2 kinds of oxidation?

A

Auto- Oxidation (spontaneous)

heat/light/metal/peroxide initiated (creates free radicals)

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37
Q

What are the 3 kinds of antioxidants?

A

Free radical scavengers
reducing agents
chelating agents

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38
Q

Mechanism for Free radical scavengers?

A

Retard/delay oxidation by rapildy reacting with free radicals

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39
Q

Mechanism for reducing agents?

A

Lower redox potential than the drug so it is more readily oxidized

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40
Q

Mechanism for chelating agents?

A

antioxidant syngergists, remove trace minerals

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41
Q

What are the 2 phases of an emulsion?

A

dispersed phase

continuous phase

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42
Q

What properties of the emulsion does the continuous phase dictate?

A

the organoleptic properties

taste, smell, feel

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43
Q

What forms can an emulsion come in?

A

oral, external, IV

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44
Q

Can oils be injected IV?

A

Yes- if can make it as an emulsion

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45
Q

How are forces dispersed in the bulk phase of an emulsion?

A

Molecules are all attracted to each other equally in all directions

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46
Q

How are forces dispersed at the boundary phase of an emulsion?

A

Forces are unequal, molecules all exhibit different forces

water- H bond, oil- london dispersion forces

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47
Q

What is interfactial tension?

A

Caused by the imbalance between force dispersion between the bulk phase and the boundary phase

  • result is constant spontaneous mvmt between phases and fewer molecules at the interface per unit area
  • increasing the area of contact btw the 2 phases creates tension
  • ** the force of this tension per unit length of interface is Interfacial tension
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48
Q

What kind of tension is interfacial tension?

A

Liquid- liquid

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49
Q

What kind of tension is Surface tension?

A

liquid- air tension

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50
Q

What increases interfacial tension?

A

Stronger intermolecular forces in the bulk phase

intermolecular forces are reduced at high temp

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51
Q

What are the 3 types of emulsifying agents?

A

Surfactive agents
hydrophilic colloids
finely divided solid particles

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52
Q

What class does surfactants fall into, amphiphillic, hydrophillic or hydrophobic?

A

Amphiphillic

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53
Q

What affect does high surfactant concentration have on surface tension>

A

it reduces surface tension (to a certian point- critical micelle concentration)

54
Q

What is hydrophile-lipophile balance (HLB)?

A

A measure of the relative contributions of the hydrophillic and lipophillic regions of a surfactant
- ranges from 0-20 for nonionic surfactants

55
Q

Low HLB = ______ lipid solubility?

A

Greater

56
Q

What does “a” stand for in the HLB equation?

A

“a”= fraction of surfactant 1 in the surfactant mixture

57
Q

What happens when the surfactant concentration increases above the critical micelle concentration?

A

The surfactant molecules self associate into micelles

58
Q

What emulsions are hydrophilic colloids used in?

A

O/W emulsions

59
Q

How do hydrophilic colloids work?

A

They increase the viscocity of water and form a multimolecular film on the surface

60
Q

Do hydrophilic colloids lower interfacial tension?

A

NO

61
Q

How do finely divided solid particles work?

A

They adsorb at the interface and form a film of particles

Hydrophilic and hydrophobic forms

62
Q

HLB greater than 10

A

W/O

63
Q

HLB less than 10

A

O/W

64
Q

When is a finely divided solid particle hydrophillic?

A

if the contact angle is less than 90 degrees

O/w

65
Q

When is a finely divided solid particle hydrophobic?

A

if the contact angle is greater than 90 degrees

W/O

66
Q

What is the Phase volume ratio?

A

Volume of Oil phase/Total volume of the emulsion

67
Q

Phase volume ratio of 0-26%?

A

O/W

68
Q

Phase volume ratio of 26-74%?

A

Either O/W or W/O

69
Q

Phase volume ration of 74-100%?

A

W/O only

70
Q

What 3 ways can an emulsion become unstable>

A
  1. Creaming
  2. Coalescence
  3. Phase inversion
71
Q

Stokes Law: What does V stand for?

A

V= velocity of sedimentation
(-) = floating droplets
high IvI- settles or floats frequently

72
Q

Stokes Law: What does d stand for?

A

d= diameter of the droplets

73
Q

Stokes Law: What does Pi stand for?

A

Pi = density of the internal phase

74
Q

Stokes Law: What does Pe stand for?

A

Pe= Density of the external phase

75
Q

Stokes Law: What does n stand for?

A

n = viscosity of the external phase

76
Q

Is creaming reversible?

A

Yes, as long as the interfacial film is effective in maintaining the integrity of the individual droplets

77
Q

Is coalescence reversible?

A

NO, leads to a layer of oil and water- broken

can’t fix by shaking

78
Q

What causes phase inversion?

A

a phase volume ration of greater than 74%

hard water can cause it also

79
Q

When making an emuslion, do the aqueous solution and oil solution need to be heated to the same temperature to mix?

A

Yes, then cooled slowly and passed through a homogenizer

80
Q

What is a suspension?

A

Liquid preparation where solid particles are dispersed through a liquid phase in which the particles are not soluble.

81
Q

Advantages for suspensions?

A 
Solubility
Chemical Stability
Taste/Palatability
Dose is flexible
Faster Dissolution than tablets
82
Q

What is the kinetic order of solutions?

A

1st order (fast)

83
Q

What is the kinetic order if suspensions?

A

Second order (slower rxn, faster dissolution and more bioavilability)

84
Q

What are the components of a suspension?

A 
Active ingredient
Vehicle
Buffer
Preservative
Flocculating agent
Structured vehicle system
wetting agent
antifoming agent
flavor/sweetener
85
Q

Required characteristics of a suspension?

A

Suspended particles should settle slowly
Particles that settle should be able to re-disperse
The suspension must flow but not to much
Particle size must remain constant

86
Q

Stokes Law: Ps

A

Ps = density of solid

87
Q

Stokes Law: Pl

A

Pl = density of liquid

88
Q

Micropulveration

A

10-50um

Most oral and suspensions

89
Q

Fluid Energy Grinding

A

<10 um
Parenteral and opthalmic suspensions
Shearing action of high velocity air

90
Q

Spray drying

A

<5umn

Solution of drug is sprayed and dried by air

91
Q

what are the 3 types of suspensions?

A

dispersed suspension
flocculated suspension
structured vehicle system

92
Q

DeltaG = ?

A

Increased surface free energy

suspension is stable when G = 0

93
Q

Ys/l = ?

A

Interfacial tension between solid and liquid

94
Q

DeltaA = ?

A

increase in surface area

want small particles–> high deltaA

95
Q

What 2 forces decrease particle size?

A

aggregation

crystal growth

96
Q

Van der Waals forces, attractive or repulsive?

A

attractive, over moderate distances but gets very strong close to the surface
not affected by formulation factors

97
Q

Electrostatic forces, attractive or repulsive?

A

Repulsive, due to the surface charge on the particle

Can be affected by formulation

98
Q

Steric forces, attractive of repulsive?

A

Repulsive

can be controlled by the formulation

99
Q

Hydration forces, attractive or repulsive?

A

Repulsive

not affected by formulation

100
Q

Net effect of interparticle forces?

A 
Repulsive force (+) little effect when particles are far apart
Attractive force (-) dominant when particles are close
101
Q

Dispersed suspension what forces are dominant?

A

Repulsive
Particles repel each other and don’t aggregate
particles settle and are difficult to re-suspend

102
Q

Controlled flocculation what forces are dominant?

A

Repulsive and attractive forces are balanced

103
Q

How does a flocculated suspension work?

A

At the secondary minimum the repulsive force is reduces a bit
when floccules settle, they are easy to re-disperse

104
Q

What type of sediment does a flocculation form?

A

High volume

105
Q

What are some examples of flocculating agents?

A

Clay
pH manipulation
Electrolytes
Non-ionic/ionic surface active agents

106
Q

What type of suspensions is clay used in?

A

Oral suspensions

107
Q

What type of suspension will you alter the pH in?

A

parenteral solutions

108
Q

How do electrolytes create flocculations?

A

Reduces the electrical barrier between particles

only works at ideal concentration

109
Q

Structured Vehicle system

A

Thickens the dispersion medium to suspend the particles

110
Q

Does the structured vehicle interfere with the availability of the drug?

A

NO

111
Q

What are 2 types of structured vehicles?

A

Clay

polymers

112
Q

Rheology

A

The study of flow characteristics

113
Q

What is shear rate?

A

dv/dr

the difference of velocity (dv) between 2 planes of a liquid separated by a distance (dr)

114
Q

What is shear stress?

A

F

the force per unite area required to bring about flow

115
Q

What are the 2 kinds of shear stress?

A

Newtonian flow

non-newtonian flow

116
Q

What are the 3 kinds of non-newtonian flow?

A

Plastic
Pseudoplastic
Dilatant

117
Q

what is the shape of a newtonian flow curve?

A

Linear

slope is constant at all shear stress

118
Q

What is the shape of a plastic flow curve?

A

liquid doesn’t flow until a certian shear stress is reached

119
Q

What is the shape of a pseudoplastic curve?

A

high force = high flow

120
Q

WHat is the shape of a dilatant curve?

A

high force = low flow

121
Q

What is f( yield value) mean?

A

Threshold of shear stress necessary to initiate flow

122
Q

Shear thinning

A

The strength of the attractive force of the secondary minimum

123
Q

Pseudoplastic suspensions?

A

No stress
typical polymer
Shear thinning

124
Q

Thixotropy

A

the ability of the system that was disturbed by an applied shear stress to return to the undisturbed structure

125
Q

Which kinds of rheology suspensions exhibit thixotropy?

A

plastic and pseudoplastic

126
Q

What does thixtropic suspensions form at rest?

A

A rigid gel matrix to stabilize the suspensions (shear stress from shaking makes it more liquid)

127
Q

Is there sedimentation with a structures vehicle suspension?

A

NO

128
Q

What is wetting?

A

displacement of air from the surface of a particle by the vehicle

129
Q

What does contact angle have to do with wetting?

A

High angle indicates poor spreading

130
Q

What is the importance of a wetting agent?

A

for rough particles, an aqueous vehicle will not enter the pores and the particle will float due to the high air content
- wetting gent reduces the surface tension of the aq vehicle to allow water to enter the pore

Dosage Forms 2 (2 decks)

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