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OU Pharmaceutics > Exam 1 Spring 17 > Flashcards

Exam 1 Spring 17 Flashcards

1
Q

Consistency can affect what?

A

flow of materials, mixing, choice of processing equipment, packaging into container, patient acceptability, physical stability, bioavailability, removal from container for use

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2
Q

Define viscosity

A
  • resistance to flow

- internal friction of a system

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3
Q

How do you determine viscosity (via layers)?

A

strength that a layer exerts on adjacent layers determines the system viscosity

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4
Q

What is the rate of shear and what is the variable that denotes it?

A

Rate of shear = G = dv/dr
dv = displacement of each layer
dr = thickness of each layer

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5
Q

What is the shearing stress and what is the variable that denotes it?

A

Shearing stress = F = Force/A

Force applied / surface area of each layer

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6
Q

What is the relationship between rate of shear and shearing stress?

A

F ∝ G

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7
Q

In variables, what is Newton’s law of flow?

A

F = ηG

the more shearing stress = the more rate of shear

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8
Q

How does viscosity affect F and G?

A

The higher the viscosity, the greater is the shearing stress required to produce a certain rate of shear

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9
Q

What are the types of non-Newtonian flow?

A
  • Plastic flow
  • Pseudoplastic flow
  • Dilatant flow
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10
Q

What is η?

A

Coefficient of Viscosity (poise)

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11
Q

In a rheogram, when you plot F vs G, you get a straight line/slop (direct relationship). What is the slope (in variable) and what does it represent?

A

1/η

- Represents fluidity (Φ)

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12
Q

In variables, define kinematic viscosity.

A

η/ρ

Viscosity/Density

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13
Q

What are the units for kinematic viscosity?

A

stokes = centipoise / [g/cm^3]

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14
Q

What are the characteristics of a rheogram of a Newtonian system?

A

Rate of shear (y) and shearing stress (x) are directly related

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15
Q

What are some examples of non-Newtonian systems?

A

ointments, suspensions, emulsions

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16
Q

What is another name for plastic flow?

A

Bingham bodies

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17
Q

What is a yield value?

A

f = the amount of force you have to apply to a non-newtonian fluid in order for it to move

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18
Q

What happens when shear stress doesn’t exceed yield value?

A

the material will act as an elastic material

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19
Q

How can you determine the yield value?

A

when shearing stress exceeds yield value, the relationship between F and G are proportion; extend the line of their slop and where it touches the x-axis is the yield value

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20
Q

What is the variable for plastic viscosity and how do you solve for it?

A

U = (F - f) / G

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21
Q

What are the contributions to yield value?

A

Vanderwaals forces and interparticle friction

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22
Q

What is an example of plastic fluid?

A

flocculated suspensions

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23
Q

What effect does flocculated suspensions have on yield values?

A

more flocculated = larger the yield value

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24
Q

What is another name for pseudoplastic flow?

A

Shear thinning systems

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25
Q

Define pseudoplastic flow

A

neither plastic or totally newton; curve starts at origin with linear approach but never reaches a straight line because slope is constantly changing; viscosity is different at every point so F value must be reported when determining viscosity

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26
Q

What is an example of pseudoplastic material?

A

natural and synthetic gums

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27
Q

What are the reasons for the curved rheogram with respect to pseudoplastic flow?

A
  • shear force aligns polymers along their long axis, reducing the internal resistance to flow
  • Uncoiling releases the entrapped solvent resulting in lowering the concentration and size of the dispersed molecules
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28
Q

What are examples of shearing stress and how does that affect viscosity of pseudoplastic materials?

A
  • Examples: shaking suspension, pumping blood, blinking eye
  • Applying stress makes the flat/linear which creates a larger surface area so that flow increases and viscosity decreases
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29
Q

What is another name for dilatant flow?

A

Shear thickening systems

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30
Q

In dilatant flow, describe the relationship between shearing stress and viscosity. What happens when you remove this stress?

A

as you increase shearing stress, the viscosity increases

when the stress is removed, the system returns to the original state of fluidity

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31
Q

What are characteristics of dilatant materials?

A
  • higher percentage of dispersed solids (more than 50%)

- small, deflocculated particles

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32
Q

What causes a solution to dilate?

A

increased stress -> increased volume -> dilate

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33
Q

In a Newtonian system, what happens when the shearing stress is removed from the system?

A

viscosity is restored at the same rate at which it was lost

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34
Q

In a non-Newtonian system, what happens when the shearing stress is removed from the system?

A

viscosity is not restored at the same rate at which it was lost

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35
Q

Define thixotropy

A

An isothermal and comparatively slow recovery, on standing of a material, of a consistency lost through shearing

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36
Q

The curves of the rheograms of thixotropic systems are highly dependent on?

A
  • the rate at which stress is applied or removed

- the length of time the material is subjected to stress

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37
Q

How does length of time the material is subjected to stress affect recovery time?

A

it’s much slower

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38
Q

Under which systems is thixotropy applicable?

A

shear-thinning systems only; plastic and pseudoplastic flow

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39
Q

What are benefits of thixotropy ?

A

upon shaking container, formulation is easily spread

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40
Q

What is negative thixotropy?

A

when a solution increases in consistency on the downcurve

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41
Q

Define rheopexy

A

A phenomenon in which a solid forms a gel more readily when sheared than when allowed to form a gel while the material is kept at rest

42
Q

Under which systems is rheopexy applicable?

A

dilatant flow

43
Q

What is the name of the property which combines solid and liquid like properties?

A

Viscoelasticity

44
Q

What are examples of viscoelastic materials?

A

creams, lotions, ointments, suppositories, suspensions, suspending agents, blood

45
Q

What does viscoelasticity measures?

A

tests rheologic ground state

46
Q

How is viscoelasticity applied in pharmeutics?

A
  • Modifications and improvement of Non-Newtonian dermatologic and cosmetic vehicles
  • Analysis of sputum for the design of mucolytic agents
  • Measurement of shear in synovial fluids during the simulated movements of joints
47
Q

What are the qualities of ideal suspensions?

A
  • high viscosity at negligible shear

- low viscosity at higher shear

48
Q

What kind of substances achieve the qualities of ideal suspensions?

A

Pseudoplastic substances with thixotropic properties

49
Q

What are examples of structured vehicles?

A
  • Carboxymethylcellulose (CMC)
  • Polyvinylpyrrolidine (PVP)
  • Xanthan gum
  • Benotnite
  • Tragacanth gum
50
Q

What are characteristics of structured vehicles?

A
  • Entrap particles in a deflocculated manner to prevent settling
  • Pseudoplastic or plastic in nature
  • Usually associated with thixotropy
  • Some sedimentation occurs anyway, but could be redispersed because of the ‘shear thinning’ property
51
Q

What is PVR?

A

Phase volume ratio = how much dispersed phase is present in how much of the dispersion medium

52
Q

Emulsion properties with change of PVR

A
  • At low PVR (<0.05) the system is Newtonian
  • s the PVR increases, the system attains Pseudoplasticity -> Plasticity
  • At PVR= 0.74, phase inversion may occur with a sharp change in η
53
Q

Emulsion properties with change of droplet size

A
  • Reduction in size increases viscosity of emulsion

- Wider the size distribution -> lower the viscosity

54
Q

Smaller particle size = increased viscosity. Why?

A

it causes disturbance with flow

55
Q

Which dosage form falls under 0.01-0.1 µm?

A

Nanoparticles, nanosuspensions

56
Q

What are nanoparticles and nanosuspensions size range?

A

0.01-0.1 µm

57
Q

Which dosage form falls under 0.1-1.0 µm?

A

Liposomal formulations

58
Q

What are liposomal formulations size range?

A

0.1-1.0 µm

59
Q

Which dosage form falls under 0.5-10.0 µm?

A

Suspensions, fine emulsions aerosols (for lung)

60
Q

What are suspensions and fine emulsions aerosols size range?

A

0.5-10.0 µm

61
Q

Which dosage form falls under 10.0- 50.0 µm?

A

Coarse emulsion particles, flocculated suspension particles, Nasal powders and droplets (Upper limit of subsieve range)

62
Q

What are coarse emulsion particles, flocculated suspension particles, nasal powders and dropets size range?

A

10.0- 50.0 µm

63
Q

Which dosage form falls under 50.0-100.0 µm?

A

(Range for fine powders) Drug particles for oral dosage forms
(Lower limit of sieve range)

64
Q

What are drug particles for oral dosage forms size range?

A

50.0-100.0 µm

65
Q

Which dosage form falls under 150.0-1000.0 µm?

A

Coarse powder range, Excipients for oral dosage forms

66
Q

What are coarse powder and excipients for oral dosage form size range?

A

150.0-1000.0 µm

67
Q

Which dosage form falls under 1000.0-3360.0 µm?

A

Average granule size

68
Q

What are average granule size range?

A

1000.0-3360.0 µm

69
Q

What are the ways in which you can measure particle size?

A
  • Geometric or projected area diameter
  • Volume diameter
  • Stroke’s diameter
  • Equivalent surface diameter
  • Aerodynamic diameter
70
Q

What are examples of measuring with geometric or projected area diameter?

A
  • microscopy

- sieving

71
Q

What are examples of measuring with volume diameter?

A
  • laser diffraction
  • light obscuration
  • coulter counter
72
Q

What are examples of measuring with Stoke’s diameter?

A

sedimentation

73
Q

What are examples of measuring with equivalent surface diameter?

A

gas adsorption

74
Q

What are examples of measuring with aerintertial imodynamic diameter?

A

inertial impaction

75
Q

What are the different types of microscope?

A
  • Transmission Electron Microscope
  • Scanning Electron Microscope
  • Optical microscope
76
Q

In microscopy, what are the different types of diameters?

A
  • Projected diameter
  • Feret diameter
  • Martin diameter
77
Q

What are advantages of microscopy?

A
  • Direct, simple, convenient
  • Provides size distribution by number
  • Can assess complete particle formation or dryness
78
Q

What are disadvantages of microscopy?

A
  • 1 dimension only

- Slow, tedious, requires statistical analysis

79
Q

What value of standard deviation is a very good powder?

A

between 1 and 2

80
Q

What are important things to consider via sieving?

A
  • Amount of powder loaded on top sieve
  • Duration of shaking
  • Composition of the material (eg. aggregation, attrition)
  • Condition of sieves
81
Q

What determines the terminal velocity of the particle?

A
  • gravitational forces

- drag forces

82
Q

What are the limitations for determining particle size via sedimentation?

A
  • Assume all particles have the same density
  • Assumes all particles are spheres, thus it has low accuracy for irregular particles
  • Does not detect powder aggregation
83
Q

What are the media for determination via volume diameter?

A
  • Conducting liquid
  • Media in which particle is not soluble
  • Air
84
Q

What are the sensing mechanisms for determination via volume diameter?

A
  • Voltage
  • Laser diffraction
  • Light scattering - Brownian motion
85
Q

Dynamic light scattering is also referred to as what?

A
  • Photon Correlation Spectroscopy
  • Quasi-Elastic Light Scattering
  • Brownian Motion
86
Q

What are the advantages of determining particle size via automated methods?

A
  • Quick and “easy” calculation of particle size and distribution
  • A wide range of particle sizes (submicron to mm) can be determined with the appropriate instrument/lenses
87
Q

What are the disadvantages of determining particle size via automated methods?

A
  • Does not discriminate between individual particles and aggregates
  • Instrument is expensive and requires maintenance and specialized training
88
Q

Gas adsorption is based on what?

A

Brunauer Emmett Teller (BET) Equation

89
Q

Air permeability method is based on what?

A

Kozeny-Carman Equation

90
Q

What are the methods to determine surface area?

A
  • Gas adsorption

- Air permeability method

91
Q

What is another name for porosity what does it measure?

A
  • aka void fraction
  • measure void spaces in a powder
  • fraction of the volume of voids in each particle over the total volume of the powder
92
Q

What are the properties that porosity influences?

A

Density, Mixing of different powders, Packing arrangements, Flow properties, Compressibility, Dissolution rate of oral solid dosage forms, Aerodynamic properties in inhalable powders

93
Q

What are the IUPAC classification on pores base on size?

A
  • Macroporous >50 nm
  • Mesoporus 2-50 nm
  • Microporus < 2 nm
94
Q

Define true density

A

For the material itself, without pores or interparticulate spaces.

95
Q

Define granule density

A

For the material itself, considers pores >10µm and inter-particular spaces

96
Q

Define bulk density

A

Relationship of the volume occupied by a determined mass of powder

97
Q

Define tapped density

A

Relationship of the volume occupied by a determined mass of powder

98
Q

Selection of capsule size is influenced by what?

A
  • bulk density
  • porosity (ε)
  • Flow-ability and compressibility
99
Q

Flow properties of powders are influenced by what?

A

size, distribution, shape, porosity, density, surface texture

100
Q

What are examples of inter-particulate forces?

A
  • Capillary forces
  • Vanderwaal forces
  • Electrostatic charge
  • Mechanical interlocking

OU Pharmaceutics (9 decks)

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