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Clinical therapeutics 1 > Powders & tablets > Flashcards

Powders & tablets Flashcards

1
Q

Define powders

A

Powders are a mixture of solid particles (mostly heterogenous system)

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2
Q

Which characterstics of powders are important for formulating drugs

A
  • particle size
  • surface area
  • Powder volume and density
  • powder flow
  • compression properties
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3
Q

Advantages of tablets

A
  • Easy to carry
  • Easy to take
  • Coveniant
  • Controllable release rate
  • Easy to scale up
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4
Q

List the 4 ways of describing particle size

A
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5
Q

List and briefly describe common methods of particle size analysis and separation

A
  • Sieving - are classified based on the sieve aperture diameter (expressed in µm) e.g. a sieve 1000 means that the sieve aperture diameter is 1000 µm (i.e. 1 mm)
  • Light microscopy (2D images)
  • Electron microscopy (SEM, TEM)
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6
Q

How does particle size effect processing

A
  • Drug bioavailability (dissolution)
  • Settling rate (suspensions)
  • When making homogenous mixture e.g. if particles are different sizes its hard to mix evenly
  • Flowability - powder flow is inversely proportional to particle size
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7
Q

Define bulk and true volume

* Bulk volume – total volume of specific mass of material, which is
occu

A
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8
Q

What is flowability

A
  • Powder flow is inversely proportional to particle
    size
  • Particle size plays a major role in
    powder flow. When the particle
    size is too small, the cohesive
    forces between particles are high
    and the flowability is reduced.
  • Other factors like density and surface area effect flowability
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9
Q

How to calculate density

A

density (p) = mass (g) / volume (cm3)

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10
Q

Methods for particle size reduction

A
  1. Cutting method
  2. Attrition method
  3. Compression method
  4. Impact method
  5. Combined (impact and attrition) - ball mill
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11
Q

Examples of equipment used for particle size reduction - ball mill

A

– Important to operate at an appropriate angular velocity (speed)
– Amount of material used is also crucial
- Angular velocity (AV) - the rate of change of the angular position of a
rotating body… or simply said, the speed at which a body is rotated
- Critical angular velocity – the velocity at which the gravitational pull becomes equal to the centrifugal forces; also know as the break-up velocity

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12
Q

Briefly discuss the factors effecting the efficiency of a ball mill

A
  • Angular velocity (AV) - the rate of change of the angular position of a
    rotating body… or simply said, the speed at which a body is rotated
  • Critical angular velocity – the velocity at which the gravitational pull becomes equal to the centrifugal forces; also know as the break-up velocity
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13
Q

Which factors are taken into account when choosing the mill used

A
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14
Q

Describe the role of different excipients - fillers

A
  • Fillers (e.g. dilutents or bulkers) used to give necessary bulk of formation
  • Colourants
  • Sweeteners
  • Flavouring agents
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15
Q

Binders as an excipient

A
  • Binders act as glue
  • e.g. gelatin, starch, calcium phosphate, lactose, calcium phosphate
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16
Q

Disintegrants as an excipient

A
  • Disintegrants promote tablet breakage into smaller particles after admission
  • e.g. crospovidine or sodium croscarmellose
17
Q

Gildants excipients

A
  • Glidants improve flowability by reducing particle friction
  • e.g. talc, magnesium stearate and colloidal silica
18
Q

Lubricants as an excipients

A
  • Lubricant reduces frictions between particles, improves flowability
  • e.g. talc, magnesium stearate, sodium stearyl fumarate
19
Q

Define positive, negative and neutral mixture

A
  • Positive mixtures: Materials that mix spontaneously and irreversibly
  • Negative mixtures: The components tend to separate
  • Neutral mixtures: Components neither tend to separate nor to mix
20
Q

What causes segregation

A
  • Density
  • Shapes
  • Sizes
21
Q

Mixing equipment

A

All container mixes around an axis

22
Q

Define granulation

A
  • The process in which a mixture of primary powder particles form larger homogenous multi-particle entities called granules
23
Q

Why granulate?

A
  • Improves powder flow
  • Improves compaction properties
  • Reduces the chances of segregation
  • Reduce volume (more convenient for storage)
  • Change material size and shape (as such surface)
24
Q

Granulation steps

A
24
Q

Advantages and disadvantages of dry granulation

A
24
Q

Identify and discuss the features of the different - microwave radiation

A
25
Q

Why is drying important

A
  • The dry granules are stronger and have better flowability.
25
Q

Advantages and disadvantages of dry granulation

A
25
Q

Identify and discuss the features of the different
granulators/dryers - fluid bed driers

A
26
Q

Identify and discuss the features of the different - spray drier

A
27
Q

Name two pieces of equipment which can be used for both granulation and drying

A

Fluid bed
Granulator
Spray bed granulator

Clinical therapeutics 1 (25 decks)

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