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Fei Lectures > L3: Suspensions > Flashcards

L3: Suspensions Flashcards

0
Q

Why may a flocculated suspension cause an inaccurate dose?

A

Due to the high sedimentation rate.

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1
Q

Name the properties of a well formulated suspension

CEMENTS

A

Chemically stable,
Easy to redisperse no hard cake at bottom,
Microbiologically stable,
Easy to pour out of bottle or injected through needle,
Nongritty,
Taste, smell, appearance, patient friendly
Slow sedimentation

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2
Q

What enables a deflocculated suspension to have an accurate dose?

A

It’s low sedimentation rate.

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3
Q

Which type of suspension allows a proper dose to be taken from the container?

A

Deflocculated

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4
Q

What type of suspension may cause an inaccurate dose?

A

Flocculated suspension.

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5
Q

Which type of suspension (f/d) is likely to cause caking during storage?

A

Deflocculated, as the sediment becomes very closely packed, hard to redisperse

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6
Q

What are the features of controlled flocculation?

A

Particles reside in secondary minimum

Enables easy redispersion, minimises settling

Products look elegant

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7
Q

What are the ways in which controlled flocculation can be achieved? (7)

WDPPFVC

A

Using Wetting agents, controlling Density,
Controlling Particle size, changing PH,
Using Flocculating agents, increasing Viscosity,
Using Co solvent

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8
Q

If particle size is reduced, this will also reduce……

A

Sedimentation rate of particles.

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9
Q

Why might particle size change during storage?

A

Due to the crystallisation

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10
Q

Particle size might change during storage due to crystallisation, how could this be prevented?

A

Using surfactants could prevent crystal growth

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11
Q

What could changing the pH of a medium achieve?

A

A desired surface CHARGE.

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12
Q

Why must a buffer be carefully considered?

A

It can influence solubility of API.

It can influence ionisation of preservatives.

It can influence the other ionic agents.

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13
Q

Name one type of flocculating agent? (S)

A

Surfactant

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14
Q

As flocculating agents, why is optimum conc. necessary for surfactants?

A

Because they are used as wetting agents as well.

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15
Q

What can a flocculated ionic surfactant do?

A

NEUTRALISE the surface charge of the drug particles.

16
Q

What can a deflocculated ionic surfactant do?

A

Provide HIGHER surface charge.

17
Q

Name one type of flocculating agent? (P)

A

Polymers

18
Q

Low concentrations of polymers causes…

A

Flocculation

19
Q

High concentration of polymers causes….

A

Deflocculation.

20
Q

As a flocculating agent, how are polymers spread within suspensions?

A

Long chain is adsorbed on the surface of particles.

Remaining part projects out into dispersing medium.

21
Q

As Flocculating agents, polymers can have dual functions. What are they?

A

Can increase viscosity of medium.

Can affect rheological properties of medium.

22
Q

Name a Flocculating agent. (E)

A

Electrolytes

23
Q

As flocculating agents, how do electrolytes work?

A

They alter the zeta potential of particles.

–> reduces thickness of electric double layer.

24
Q

What are suspending agents used for?

A

To modify viscosity.

25
Q

What does increasing viscosity do to sedimentation?

A

Slows down the sedimentation rate.

26
Q

Name a general characteristic of an ideal suspending agent.

R

A

Must have favourable rheological properties.

27
Q

Name a general characteristic of an ideal suspending agent.

IF

A

Must be readily/uniformly incorporated in the formulation.

28
Q

Name a general characteristic of an ideal suspending agent.

DD

A

Must be readily dissolved and dispersed in water.

29
Q

Name a general characteristic of an ideal suspending agent.

CF

A

Must ensure a controlled flocculation

30
Q

Name a general characteristic of an ideal suspending agent.

Toxicity

A

Must be inert,non toxic, and free from incompatiblities.

31
Q

Name a general characteristic of an ideal suspending agent.

D/A

A

Must NOT influence the dissolution rate or absorption rate.

32
Q

What are the 2 things that co solvents do

A

Help with wetting.

Increase viscosity.

33
Q

Explain how co solvents help with wetting.

A

Can penetrate the loose agglomerates of powder,

–> displacing air phase from particle pores.

–> therefore reduce interfacial tension between liquid and air.

34
Q

Are co solvents miscible with water? Example?

A

YES.

Glycerol.

35
Q

Name the factors on which preservatives are selected on.

S,P,W,S,N,C,TO.

A
  • SITE of use -must have good PHYSIOCHEMICAL properties
  • be effective against WIDE range of microorganisms -STABLE
  • NONTOXIC, -COMPATIBLE with other ingredients, -free of TASTE/ ODOUR
36
Q

Why should there be adequate airspace above the suspension when packaging?

A

To permit shaking.

37
Q

Why should suspensions be shaken before use?

A

To redisperse particles, to ensure a uniform distribution of solid in the vehicle, and therefore an accurate dose.

Fei Lectures (8 decks)

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