Suspensions

Question 1

What is the definition of a suspension?

Answer 1

A pharmaceutical suspension that is a coarse dispersion that contains the following:

1. Finely divided insoluble particulate
2. Suspended in a liquid or semi-solid medium

Question 2

What is the particle size of suspensions?

Answer 2

Ranges from 1-100 micrometers

FIne dispersion (1-50 micometers)

Coarse dispersion (50-100 micrometers)

Question 3

What are some advantages of suspensions?

Answer 3

Ability to deliver poor water soluble drugs

Suitable for patients who have difficulty swallowing

Easier to mask taste

Chemical stability

Sustained release (

Can be given for systemic or local effects/treatment

Question 4

What are some disadvantages of suspensions?

Answer 4

Physical instability, will settle relatively quickly due to a lack in uniformity of the dose

Manufacturing difficulties

Question 5

What are some qualities expected in a good suspension?

Answer 5

PArticles should not precipitate quickly

Should redispersed quickly by shaking product

Correct viscosity to pour the bottle/flow though an administration needle

Finer particles allow us to easily spread our product

Question 6

What is the internal phase?

Answer 6

This includes the drug/active ingredient

They are also divided into hydrophobic (not wetted by water, but by oils) and hydrophobic solids (readily wetted by water)

Question 7

What are some examples of a hydrophillic solid used in a suspension

Answer 7

Clays (kaolin, talc, magnesium

Question 8

What are some examples of hydrophobic solids in suspensions?

Answer 8

Most drugs are hydrophobic

ex. Charcoal, sulfur, aspirin, and phenobarbital

Question 9

What is the external phase?

Answer 9

It is the dispersion medium

Question 10

What is considered when selecting an external phase/dispersion medium?

Answer 10

Safety
Density
Viscosity (important for formulation stability)
Taste
Stability

Question 11

Can alcohol content be above 10% and still be classified as a suspension?

Answer 11

No, if alcohol content is higher than 10%, it is not considered a suspension

Question 12

What are structured vehicles?

Answer 12

They are aqueous dispersions of polymeric materials

Ex. Acacia (0-2%)

Tragacanth - 0.5-5%

Carbopol (0-0.5%)

Methyl cellulose derivatives are set between (0.5-5%)

Colloidal silicon dioxide (1.5-3.5%)

Question 13

What are the properties of structured vehicles depending on their concentration?

Answer 13

At low concentrations, structured vehicles are effectively protective colloids

At high concentrations, it is a viscosity-inducing agent

Question 14

What are some flocculating agents used in suspensions?

Answer 14

Electrolytes (capable of reducing zeta potential, deflocculation is reduced)

Ionic surfactants (neutralize some of the surface charges, increase flocculation)

Polymeric Flocculating Agents (form a gel-like network to cross-link the suspended particles)

Question 15

What are some viscosity modifiers used in suspensions?

Answer 15

1. Polysaccharides (only used in extemporaneously compounding) ex. Acacia gum, tragacanth, alginates
2. Water Soluble Cellulose Derivatives
   Ex. Methylcellulose and microcrystalline cellulose
3. Hydrated silicates
   Ex. Bentonite
4. Acrylic acid polymers
   Ex. Carbopol
5. Colloidal Silicon Dioxide

Question 16

What are the different types of suspensions according to administration type ?

Answer 16

Oral suspensions (antibiotics, antacids, radiplaque suspensions)

Topical suspensions (calamine lotions)

Parenteral suspensions (I.M, S.C, intralesional, intrarticular)

Sterile Topical Suspension (ophthalmic suspensions)

Cosmetics

Question 17

What are the different types of suspensions according to physical structure?

Answer 17

Deflocculated suspensions:
Small discrete units, settle slower and pack tighter (cake formation)

Flocculated suspension (most common form):
Dispersed particles form loose aggregates (flocs)

Rate of sedimentation is rapid (water is trapped)

Easily redispersed

Question 18

What are the properties of a well formulated pharmaceutical suspension?

Answer 18

Must be easily resuspendable

The dispersed phase must also be long enough to remove a dose

Particles should be sufficiently small to appear smooth

Has suitable viscosity (for stability, function, and aesthetic)

Question 19

What happens when zeta potential is high?

Answer 19

Repulsive forces are greater than attractive forces

System will be dispersed or deflocculated (individual particles), therefore harder to resuspend

Question 20

What happens when zeta potential is low?

Answer 20

Attractive forces dominate repulsive potential

System is flocculated (prevents caking), can be resuspended relatively easily

Question 21

Review slide 39 to study suspension strategy

Question 22

What are some general compounding tips?

Answer 22

Wear a dust mask if you are working with powders

Wet powders that aerosolize easily with alcohol, water, or mineral oil

Question 23

What is the reason and solution for caking in a suspension?

Answer 23

Reason: High zeta potential, therefore deflocculated

Solution: Flocculate

Question 24

What is the reason and solution for crystal growth in suspensions?

Answer 24

Reason: Partial solubility, temp fluctuations, and heterogenous particle size

Solution: Select insoluble form of the drug, keep at constant temp, ensure narrow particle size distribution

Question 25

What is the reason and solution of poor redispersibillity in suspensions?

Answer 25

Reason: Deflocculated suspension, caking, viscosity is to high

Solution: Flocculate, and keep viscosity optimal

Question 26

What is the reason and solution for cap lock in suspensions?

Answer 26

Reason: sugar in the formula

Solution: Use a mix of sugar and artificial sweetener

Question 27

What is the reason and solution for settling in suspensions?

Answer 27

Reasons: Low viscosity and particles

Solution: Increase viscosity and reduce particle size

Question 28

What are the reasons and solutions for flavour changes in suspensions?

Answer 28

Reasons:
Incompatibility

Solutions:
Select another flavour

Question 29

What are the reasons and solutions for colour changes in suspensions?

Answer 29

Reasons:
Incompatibility, and too much aeration

Solution:
Solve incompatibility, and avoid air bubbles