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Pharmacy Lab > Dosage forms exam 1 my flashcards > Flashcards

Dosage forms exam 1 my flashcards

1
Q

What are 3 types of liquid dosage forms?

A

SolutionEmulsionSuspension

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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 dropletsOil 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 issuesGood bioavailabilityEasy to manufacture

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6
Q

What are the 6 components of a solution?

A

Active ingredientSolventBufferPreservativeAntioxidant- Chelating agentFlavor/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 concentrationC = [HA] + {A-]

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12
Q

What are 4 common buffers?

A

Citric acidacetic acidglycinephosphoric 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 stability2. 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 capacity2. Reduce volume3. Administer slowly
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15
Q

What is the purpose of antimicrobial preservatives?

A
  1. Protects the patient from pathogens2. 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 sterileFor 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 sterileMay 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 sterileMust 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 mLNeed 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 formsCan be contaminated with salmonellaCheck 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 organisms2. Soluble in formulation3. Non toxic4. Stable
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26
Q

List 5 pharmaceutical preservatives?

A
  1. Alcohols2. Acids3. Parabens4. Quaternary Ammonium Compounds
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27
Q

Characteristics of ethanol as a preservative?

A

Requires a concentration of greater than 15 percentoral products onlycan be lost because it is so volatile

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28
Q

Characteristics of Benzyl Alcohol as a preservative?

A

Local anethetic actionBurning taste- not used orallyWater soluableStable over wide pH rangeHighly 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 orallyLipophillic and less lipophillic varieties (depends on length of hydrocarbon R group) low soluabilityCan 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 solidsChemical 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 scavengersreducing agentschelating 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 phasecontinuous phase

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42
Q

What properties of the emulsion does the continuous phase dictate?

A

the organoleptic propertiestaste, 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 forceswater- 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 agentshydrophilic colloidsfinely 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 particlesHydrophilic 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 degreesO/w

65
Q

When is a finely divided solid particle hydrophobic?

A

if the contact angle is greater than 90 degreesW/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. Creaming2. Coalescence3. 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- brokencan’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

SolubilityChemical StabilityTaste/PalatabilityDose is flexibleFaster 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 ingredientVehicleBufferPreservativeFlocculating agentStructured vehicle systemwetting agentantifoming agentflavor/sweetener

85
Q

Required characteristics of a suspension?

A

Suspended particles should settle slowlyParticles that settle should be able to re-disperseThe suspension must flow but not to muchParticle 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

10-50umMost oral and suspensions

89
Q

Fluid Energy Grinding

A

<10 umParenteral and opthalmic suspensionsShearing action of high velocity air

90
Q

Spray drying

A

<5umnSolution of drug is sprayed and dried by air

91
Q

what are the 3 types of suspensions?

A

dispersed suspensionflocculated suspensionstructured vehicle system

92
Q

DeltaG = ?

A

Increased surface free energysuspension is stable when G = 0

93
Q

Ys/l = ?

A

Interfacial tension between solid and liquid

94
Q

DeltaA = ?

A

increase in surface areawant small particles–> high deltaA

95
Q

What 2 forces decrease particle size?

A

aggregationcrystal growth

96
Q

Van der Waals forces, attractive or repulsive?

A

attractive, over moderate distances but gets very strong close to the surfacenot affected by formulation factors

97
Q

Electrostatic forces, attractive or repulsive?

A

Repulsive, due to the surface charge on the particleCan be affected by formulation

98
Q

Steric forces, attractive of repulsive?

A

Repulsivecan be controlled by the formulation

99
Q

Hydration forces, attractive or repulsive?

A

Repulsivenot affected by formulation

100
Q

Net effect of interparticle forces?

A

Repulsive force (+) little effect when particles are far apartAttractive force (-) dominant when particles are close

101
Q

Dispersed suspension what forces are dominant?

A

RepulsiveParticles repel each other and don’t aggregateparticles 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 bitwhen 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

ClaypH manipulationElectrolytesNon-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

Claypolymers

112
Q

Rheology

A

The study of flow characteristics

113
Q

What is shear rate?

A

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

114
Q

What is shear stress?

A

Fthe force per unite area required to bring about flow

115
Q

What are the 2 kinds of shear stress?

A

Newtonian flownon-newtonian flow

116
Q

What are the 3 kinds of non-newtonian flow?

A

PlasticPseudoplasticDilatant

117
Q

what is the shape of a newtonian flow curve?

A

Linearslope 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 stresstypical 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

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