Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

S1 Pharmaceutics > Suspensions > Flashcards

Suspensions Flashcards

1
Q

What is a disperse system ?

A
  • a two-phase heterogeneous system in which an insoluble or immiscible dispersed phase is distributed through a continuous phase.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is a pharmaceutical suspension?

A
  • a liquid disperse system consisting of particles distributed within a liquid vehicle.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Reasons for formulating pharmaceutical suspensions

A
  • To deliver poorly water-soluble drugs which cannot be formulated as aqueous solutions
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Ways to reduce sedimentation rate

A

Particle size reduction – increases diffusion

Increase medium density – e.g. adding dextrose.

Increase temperature

Increase medium density

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Why is the difference between a drug solution and suspension ?

A
  • solution contains a dissolved drug
  • suspension contains undiscovered drug particles suspended in a liquid
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is a flocculated suspension?

A
  • suspended particles form into floccules (clumps) rather than separate particles
  • re dispersion is easy
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is a deflocculated suspension?

A
  • Particles are individually dispersed
  • form a cake at the bottom
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Key properties of an oral suspension for uniform dosing:

A
  • Particles settle slowly
  • readily + uniformly re-dispersed upon shaking
  • size remains consistent over time
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

3 methods of particle movement in suspensions?

A
  • Brownian motion
  • gravity
  • external agitation (shaking by patients)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is brownian diffusion?

A
  • Irregular movement within the medium
  • diffusion from high concentration to low
  • small particles
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is sedimentation?

A
  • It is the downward particle movement due to gravity
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Which system is better to use to ensure reproducibility?

A
  • A flocculated system
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Which system ensures a slow sedimentation rate?

A
  • Deflocculated system
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is relationship between particle size and sedimentation?

A

As particle size decreases sedimentation decreases
- submicron suspension (small) = Brownian motion keeps particles dispersed
- large particles = greater effect of gravity so settle quicker

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Ways to reduce sedimentation rate

A
  • Reduce particle size = increases diffusion
  • reduce particle density
  • increase medium density eg. Adding dextrose
  • increase temperature
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is zeta potential?

A
  • Zeta potential provides a measure of the magnitude of the electrostatic or charge repulsion/attraction between particles at the slipping plane, between the particle and its associated double layer and the the solvent.
17
Q

3 Features of electrical double layer

A
  • diffuse layer = ions diffuse more freely around the particle
  • stern layer = attracts ions of opposite charge (+ve), ions are lightly bound to surface, drugs give negative charge in liquid
  • slipping plane = boundary between stern + diffuse layer
18
Q

What happens when zeta potential is reduced?

A
  • attractive forces (van der waals) overcome the faces of repulsion
  • particles come together to form floccules
19
Q

What happens if suspension has a large negative or positive zeta potential ?

A
  • particles tend to repel each other
20
Q

effect of excipients like ionic salts on electrical double layer ?

A
  • increase number of mobile charges
  • low conc = affects diffuse layer, easier to neutralise the particle charge + thinning the layer
  • high conc = affects fixed/stern layer, charge on partical surface decreases
21
Q

effect of surfactants on electrical double layer ?

A
  • CMC is the conc of surfactants above
    which the micelles form
  • above CMC, micelles form with a hydrophobic core
  • below CMC - surfactants will cover the particles surface
  • conc below CMC used to reduce tension between particle + liquid
22
Q

what are properties of an ideal suspension ?

A
  • appropriate viscosity
  • no hard caking
  • sedimentation
  • dispersion
23
Q

what are suspending agents used for ?

A
  • reduce particle sedimentation
23
Q

what are chemical stabilisers used for ?

A
  • improve chemical stability of the drug
23
Q

what are flocculating agents used for ?

A
  • decrease zeta potential
  • cause aggregation of particles
23
Q

what are wetting agents used for ?

A
  • reduce tension between particle + liquid
  • eg. surfactants below CMC
24
Q

what are preservatives used for ?

A
  • to prevent microbial growth

S1 Pharmaceutics (7 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions