Suspension Dosage Forms Flashcards

1
Q

What is a suspension?

A

Course dispersion in which insoluble particles, generally >1micrometer, are dispersed within a liquid medium which is usually aqueous

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2
Q

What are the characteristics of an ideal suspension?

A

Homogeneous during dosing
Easy to redisperse
Poor viscosity
Particles should be small and uniform

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3
Q

What does ratio r compare?

A

Sedimentation layer volume (Vs) to total suspension volume (Vt)

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4
Q

How do you prevent caking in a suspension?

A

Use a flocculating agent

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5
Q

What is zeta potential?

A

Magnitude and type (+ or -) of the electrical potential at the slipping plate

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6
Q

What happens when there is entropic (steric) effects?

A

Two particles come into close contact, the polymer chains start to overlap
Which leads to a loss in the freedom of motion of the polymer chains
The is situation is thermodynamically unfavourable and forces droplets apart again

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7
Q

What happens when there is osmotic forces (solvation)?

A

When two particles come into close contact the polymer chains start to overlap, effectively lending to a concentrated polymer solution.
This induces osmotic gradient

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8
Q

What is flocculation?

A

Form into an aggregated lumpy or fluffy mass

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9
Q

What happens when the attractive forces (Va)>(Vr)?

A

Weakly attracted clusters form
Re disperse upon shaking

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10
Q

What happens when attractive forces (Va)<(Vr)?

A

Close packed arrangement at the bottom of container
Cannot be redispersed

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11
Q

What are the characteristics of flocculated systems?

A

Particles are aggregated
Fast sedimentation
Fluffy sediment
Large sedimentation volume

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12
Q

What are the characteristics of deflocculated systems?

A

Particles remain as discrete units
Slower sedimentation
Compact sediment
Small sedimentation volume

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13
Q

how to achieve controlled flocculation?

A

particle size
use of electrolytes to control the electrostatic repulsion
addition of floccuating agents

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