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PHRM2202 > WEEK 1: Solid Dosage Forms > Flashcards

WEEK 1: Solid Dosage Forms Flashcards

1
Q

Pharmaceutical companies give a single number for an average sized particle of a particular drug. If drug particles are organic in shape, how is this determined?

A

This is done using the “equivalent sphere” method, which involves the assumption that every particle can be approximated to a sphere, and this can be characterised by a diameter.

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2
Q

Match the four approaches for measuring diameter with their definitions:

a. Projected perimeter diameter
b. Projected area diameter
c. Feret’s diameter
d. Martin’s diameter

  1. Diameter of a circle having the same area
  2. Distance between widest points
  3. Diameter of a circle having the same perimeter
  4. Length of line dissecting the particle
A

a3, b1, c2, d4

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3
Q

What are some limitations to measuring particles size using sieving

A
  • each sieve collects a range of particle sizes
  • results are time-dependent
  • electrostatic forces increase as particle size reduces, and particles that are less than 40 µm can be quite difficult to separate and so behave as larger particles
  • sieving can cause fragile particles to break, changing their particle size
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4
Q

A course powder is greater than …µm

A

> 355 µm

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5
Q

A moderately fine powder ranges between … and …µm

A

180 - 355 µm

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6
Q

A fine powder ranges between … and …µm

A

125 - 180 µm

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7
Q

A very fine powder is less than …µm

A

< 125 µm

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8
Q

A micronised / ultrafine powder is less than …µm

A

< 10 µm (most < 5 µm)

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9
Q

What is Stokes diameter?

A

A method that measures particle size using sedimentation. particles must be suspended in a liquid. The speed at which the particles settle is the diameter of the equivalent sphere having the same settling velocity.

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10
Q

(Regarding Strokes diameter)
For … particles it would take too long to wait for settling with gravity, so a … is used to increase the speed of sedimentation.

A

small
centrifuge

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11
Q

What are the limitations to measuring particles using Strokes diameter?

A
  • There’s a limited particle size range that can be used because Brownian motion causes problems below 1µm
  • Above 50µm settling can be turbulent.
  • It can’t be used for particles that aren’t close to be spherical because irregular shapes sediment more slowly.
  • It can’t be used for mixtures of powders that have different densities.
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12
Q

Match the method of particle measurement with what it measures:

a. Coulter counter
b. Strokes diameter
c. Laser light scattering

  1. particle size
  2. projected area diameter and sometimes volume diameter
  3. volume diameter
A

a3, b1, c2

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13
Q

In order to measure volume diameter through the Coulter counter test particles must be capable of being suspended in an … solution.

A

electrolyte

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14
Q

A Coulter counter measures the …. crossing through an aperture, and then when a … comes along it displaces a volume of electrolyte solution and this changes the electrical current. The machine converts this signal into a … volume.

A

electrical current
particle
displacement

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15
Q

Match the method of particle measurement with the size of particles it can measure:

a. Coulter counter
b. Strokes diameter
c. Laser light scattering

  1. > 0.2µm
  2. > 0.1 µm
  3. 50µm - 1µm
A

a1, b3. c2

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16
Q

When using laser light scattering to measure a particles size, the size is estimated by the … and … of …

A

intensity and angle of diffraction.

17
Q

T or F
(Regarding laser light scattering)
A smaller particle will have a small angle diffraction whilst a larger particle will have a comparatively large angle of diffraction.

A

F
vice versa

18
Q

…. is a type of laser light scattering that can be used for particles that are smaller than around 100 nm, which are termed ‘colloidal’ in size.

A

Dynamic light scattering (DLS)

19
Q

Which of the following techniques provide the volume diameter of an equivalent sphere?

A
20
Q

T or F
When we talk about particles of a powder, we are taking about only one type of molecule, e.g. an API such as paracetamol or an excipient such as starch.

A

T

21
Q

T or F
Granules can only be made up of particles of the same molecule

A

F

22
Q

List some characteristics that are affected by particle size and shape.

A

dissolution rate
sedimentation rate
powder flow and mixing
compressibility

23
Q

Which of the arithmetic means require the number of particles to be known?

A

Number mean diameter and Surface-number mean diameter

24
Q

T or F
Intra-particulate voids are as important to consider as inter-particulate voids.

A

T

25
Q

If a particle is said to be porous this means it has…

A

intra-particulate voids.

26
Q

T or F
All particles have inter-particulate voids

A

T

27
Q

T or F
A single material can have numerous true densities

A

F
Only 1

28
Q

True density of a non-porous material is measured by …

A

liquid displacement.

29
Q

When it comes to porous materials, …. is used to measure true density.

A

gas displacement

30
Q

When the intra-particulate voids are included with the particle in the measurement of density, then we are measuring what is known as … density.

A

granule

31
Q

Granule density is measured by … displacement.

A

mercury

32
Q

Why is mercury used to measure granule density?

A

Mercury fills inter-particulate voids but cannot enter intra-particulate voids.

33
Q

The density of a whole powder, including all of the void spaces, is known as the … density.

A

bulk

34
Q

T or F
Tapped density using 500 taps will mean that the powder takes up a smaller volume than the 3-tap method, and so therefore the density value is smaller

A

F
The density value will be larger

35
Q

T or F
Powders with low bulk density take up more space than powders with a higher bulk density

A

T

36
Q

T or F
True density is always a larger number than bulk density

A

T

37
Q

T or F
A bulk density value of 0.6 g/mL means that 1 g of powder will take up 0.6 mL in volume

A

F

38
Q

What are the two main influences of total porosity?

A

particle size and shape, because these affect the way that particles pack together.

39
Q

T or F
Total porosity can be altered by manipulating inter-particulate porosity.

A

T

PHRM2202 (8 decks)

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