W9 Suspension Dosage forms

Question 1

Examples of everyday suspensions

Answer 1

• Whole milk (milk fat globules and casein protein in water)
• Peanut butter (finely ground peanuts in oil)
• Hot chocolate (cocoa powder slowly sediment)
• Muddy river water (soil particles in muddy water settle)

Question 2

Pharmaceutical applications of suspensions

Answer 2

Suspensions are needed for:
* All new products (unless problematic)
* Paediatrics
* Geriatrics
* Administration of water-insoluble drugs
* Enteral fed patients

Question 3

Suspension definition

Answer 3

• Course dispersion in which insoluble particles, generally > 1 μm, are
  dispersed within a liquid medium which is usually aqueous
• Settle out
• Shake to stay suspended

Question 4

What is an ideal suspension? (4)

Answer 4

*Homogeneous during dosing
*Easy to re-suspend
*Proper viscosity
*Particles should be small and uniform in size

Question 5

In deflocculated systems, the particles are…

Answer 5

not associated

Question 6

During flocculation, the particles come together attracted by…

Answer 6

weak forces to form flocs

Question 7

In suspensions, what does pressure on the individual particles lead to?

Answer 7

Close packing of the particles at the bottom, irreversibility bound together to from a cake

Question 8

How is caking of a suspension prevented?
Examples? (3)

Answer 8

Including a flocculating agent in the formulation
Electrolytes, Surfactants, Polymers

Question 9

Electrostatic effects
What 2 layers makes up the electrical double layer of ions?

Answer 9

1. Stern layer
2. Diffuse layer

Question 10

What is meant by ‘Zeta potential’?
What does a low/high zeta potential mean?

Answer 10

Magnitude and type (+ or –) of the electrical
potential at the slipping plane
* Low zeta potential (0 to 5 mV) are
prone to aggregate
* Zeta potential > 30 mV tend to
remain dispersed

Question 11

Entropic (steric) effects example

Answer 11

• An attractive bridging force (a) is replaced with a repulsive steric force (b) in adsorbing polymer solutions when the concentration increases

Question 12

Flocculated system vs Deflocculated systems

Answer 12

Flocculated systems:
- Particles are aggregated
- Fast sedimentation
- “Fluffy sediment”
- Large sedimentation volume

Deflocculated systems:
- Particles remain as discrete units
- Slower sedimentation
- Compact sediment
- Small sedimentation volume

Question 13

How to achieve controlled flocculation? (5)

Answer 13

• Particle size
• Use of electrolytes to control the electrostatic repulsion
• Addition of flocculating agents (and their concentrations)
• Surfactants
  Ionic – Zeta potential
  Non-ionic bridging
• Polymers
  Bridging
  Also increase viscosity