Brainscape's Knowledge GenomeTM

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


See full index

PM2B Spring Amy L > Suspensions As Dosage Forms > Flashcards

Suspensions As Dosage Forms Flashcards

1
Q

List 4 ways that suspensions can be administered

A

Oral
Topical
Pareneteral
Inhalations

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

Describe oral administration of solutions

A

Materials need to be in finely divided form in gastrointestinal tract
More palatable than solutions in children

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

What is benefit of administering suspensions via the parenteral route?

A

Can control the rate of absorption of the drug

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

What is the benefit of having suspensions inhaled?

A

Prolonged release of volatiles

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

What kind of drugs are formulated as suspensions?

A

Poorly soluble drugs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

List 3 advantages of using pharmaceutical suspensions

A
  1. Useful for formulation of low solubility drugs
  2. Effective at masking taste
  3. Ideal for patients who have difficulty swallowing solid dosage forms
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

List 3 disadvantages of using pharmaceutical suspensions

A
  1. Fundamentally unstable
  2. Aesthetic suspension formulation difficult to attain
  3. Bulky formulations
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

List 3 desired features of a pharmaceutical suspension

A
  1. Dispersion should settle slowly and be easily dispersed with gentle shaking
  2. Particle size of dispersed medium should remain constant
  3. Suspension should pour readily and evenly
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

List 2 parameters of the dispersed phase we can control

A
  1. Particle size

2. Surface properties of particles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

List 2 parameters of the vehicle/continuous phase we can control

A
  1. Viscosity
  2. Use of electrolytes
  3. Addition of surfactants
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What affect does particle size have on the suspension?

A
  • Small fine powder for slow sedimentation
  • Particles >5um = gritty texture
  • Particle size controls rate of dissolution
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How can crystal growth in the suspension occur?

A
  • Smaller particles dissolve and larger particles grow

- Happens on storage where temperature variation can alter solubility of a slightly soluble drug

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

How can crystal growth be prevented?

A

Polymeric colloids or surfactants

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

List 2 ways that the sedimentation rate can be reduced

A
  1. Reducing size of particle (h/e fine particles can form cakes)
  2. Increasing viscosity of medium
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How does the shape of the particles affect sedimentation of the suspension?

A

Barrel shaped = more stable dispersions

Needle shaped = cake

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is DVLO theory?

A

An explanation of the stability of a colloidal suspension
It describes the balance between electrostatic repulsion and Van der Waals attraction = total interaction energy
Therefore - system will be stable if repulsive forces prevent interaction between particles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What does the primary minimum represent?

A

Coagulation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What does the first peak in an energy of interaction vs particle separation graph represent?

A

The energy barrier to coagulation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What does the secondary minimum represent?

A

Flocculation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What are the attractive interactions involved in DVLO theory?

A

Van der Waals interactions

= a volume force

21
Q

What are the repulsive interactions involved in DVLO theory?

A

Forces between bound surface ions = a surface force

Electrostatic & steric hindrance between polymer chains

22
Q

What is the electrical double layer?

A

A structure which appears on the surface of a solid when it is exposed to a fluid
2 parallel layers of charge surrounding the solid
1st layer = the surface charge = ions adsorbed onto the object due to chemical interactions
2nd layer = diffuse layer = ions attracted via the surface charge

23
Q

What affects the thickness of the double layer?

A 
Electrolyte concentration (increase = decrease in thickness)
Surface potential (charge on particle)
24
Q

What does the approach of particles coated with hydrated polymer lead to?

A

Leads to repulsion of particles

Due to steric hindrance (positive enthalpy change & negative entropy change) and osmotic pressure

25
Q

List 5 problems that need to be overcome into order to create a stable suspension formulation

A
  1. Sedimentation
  2. Caking
  3. Flocculation
  4. Particle growth (crystals?)
  5. Adhesion to container wall
26
Q

What is the main role of excipients in suspensions?

A

To stabilise the suspension of particles

Control sedimentation and limit aggregation or crystal growth

27
Q

What is the affect of adding wetting agents to a suspension?

A

Reduces surface tension

Reduce interfacial tension between particle and dispersed medium

28
Q

Define: Wettability

A

The tendency of 1 liquid to adhere to a solid surface in the presence of other immiscible fluids

29
Q

What does deflocculation lead to?

A

A cake or clay formation
Slow sedimentation so prevents medium becoming trapped (like in flocculation) = compacted
Very difficult to redisperse

30
Q

What is flocculation?

A

Secondary minima
Loose aggregation
Particles sediment rapidly entrapping continuous phase and remaining discrete
This means it is easily dispersed

31
Q

What happens if the electrolyte concentration is increased too much?

A

The repulsive interactions weaker and eventually barrier to coagulation is removed = coagulated and stable aggregate - bad

32
Q

What is a potential problem of wetting agents?

A

Can often lead to a deflocculated suspension due to reduction in interfacial tension

33
Q

What is controlled flocculation?

A

Prepare partially flocculated system:

  • Control particle size
  • Control zeta potential (by adding electrolytes)
  • Addition of polymers (to promote crosslinking)
34
Q

What is the role of flocculating agents?

A

Support the ‘floc’ and increase sedimentation volume

35
Q

List 3 things that could be used as flocculating agents

A
  1. Electrolytes - ions of opposite charge will reduce thickness of double layer = secondary minimum (flocculation)
  2. Surfactants = affect electric (zeta) potential
  3. Hydrophilic polymers = adsorb to particles leading to loosely flocculated structures
36
Q

What affect does the addition of electrolyte have?

A

Electrolyte reduces thickness of double layer = flocculated system
H/e add to much = coagulation

37
Q

How can a system go from deflocculated to partially flocculation?

A

Add flocculating agent:

Electrolytes, surfactants or hydrophilic polymers

38
Q

Define: Newtonian flow

A

Constant viscosity regardless of shear rate

Deflocculated system

39
Q

Define: Non-Newtonian flow

A

Change in viscosity with increasing shear rate

Flocculated system

40
Q

Define: Shear rate

A

Gradient of velocity in a flowing material

41
Q

How is sedimentation quantified?

A

Ratio of sedimentation layer volume:total suspension volume

42
Q

What is the degree of flocculation measured by?

A

Determined by sedimentation volume

43
Q

Why are electrolytes common excipients in suspensions?

A

Electrolytes control flocculation

44
Q

Why are surfactants common excipients in suspensions?

A

Act as wetting agents and flocculauting agents

45
Q

Why are hydrophilic polymers common excipients in suspensions?

A

Enhance physical stability - wetting/flocculating agents

Enhance rheological stability - viscosity agents

46
Q

How does the viscosity of a suspension affect its absorption in the GIT?

A

High viscosity = slow dissolution

47
Q

How does the suspension’s slower dissolution rate than solution make it preferable in some circumstances?

A

Slower dissolution rate = can control rate of release in injection

48
Q

List 5 criteria of suspending agents

A
  1. Be readily and uniformly incorporated into formulation
  2. Be readily dispersed in water without special techniques
  3. Ensure no caking
  4. Must not influence dissolution rate or absorption rate
  5. Be non-toxic

PM2B Spring Amy L (16 decks)

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