Suspensions- Dr.Mirza

What is continuous phase of a suspension?

What is continuous phase of a suspension?

liquid

What is the dispersed phase of a suspension?

solid

Definition of a pharmaceutical suspension:

a liquid dosage form containing finely divided drug particles distributed somewhat uniformly throughout a vehicle in which the drug exhibits a minimum solubility

A suspension is a coarse dispersion of finely divided ___________ solid particles in a liquid medium.

a. soluble

b. insoluble

b

When would a suspension be prepared?

• exam question

1. to administer an INSOLUBLE compound as a liquid

2. to diminish the unpleasant taste of an insoluble compound

3. to modify the release rate of a drug

4. to improve stability

What are the primary forces responsible for particle aggregation in suspensions and the main forces in the DVLO Theory of Particle Interaction?

• exam question

1. van der waals forces

2. electrostatic repulsion forces

What is caking in terms of suspensions? Can a suspension be used after caking?

• caking is forming an irreversible sediment(cake) layer at the bottom of the container

• makes the suspension unusable

How can particle aggregation be prevented?

• exam question

by using particles that have similar charges

What flocculating agent would you use for controlled flocculation?

• exam question

• electrolyte (most common)

• charged surfactant

• charged polymer

(think anything charged)

Answer the following about a deflocculated suspension:

1. How do the particles exist in the suspension?

2. Is the rate of sedimentation slow or high?

3. Does the suspension look cloudy or clear?

1. particles exist in suspension as separate entities.

2. slow rate of sedimentation

3. cloudy

Answer the following about a flocculated suspension:

1. How do the particles exist in the suspension?

2. Is the rate of sedimentation slow or high?

3. Does the suspension look cloudy or clear?

1. particles form loose aggregates

2. high rate of sedimentation

3. clear

Would you see caking in a deflocculated or flocculated suspension?

deflocculated

Why are we using Stoke’s Law?

• exam question

to measure sedimentation rate

Examples of suspension excipients that are vehicles:

• memorize

• purified water

• non-aqueous solvents

Examples of suspension excipients that are wetting agents (surfactants):

• memorize

• SDS (sodium dodecyl sulfate)

• benzalkonium chloride

• Tweens

• Spans

Examples of suspension excipients that are flocculating agents:

• memorize

• KH2PO4

• SDS

• Xanthan gums

• carbopols

Examples of suspension excipients that are viscosity modifiers:

• memorize

• cellulose derivatives

• clays

Examples of suspension excipients that are buffers:

• memorize

• citrate

• phosphate

What are the disadvantages of suspensions?

• unstable systems

• hard to formulate

• bulky

What are the quality control factors of suspensions?

• exam question

• appearance

• odor

• weight/volume

• extent of settling

• ease of dispersibility

• pourability

• pH

• viscosity

• active drug content

Suspensions should be labeled…

shake well before use