Suspensions

Question 1

Define ready to use form

Answer 1

Drug is already dispersed in the vehicle with or without any preservativese or any other additives

Question 2

Define dry powders for suspension

Answer 2

Drug is mixed with suitable suspending and dispersing agents, that can be dissolved in a vehicle by simple agitation

Question 3

Application of suspensions

Answer 3

• Used if can’t swallow solid dosage forms
• Drugs are unstable in aqueous solutions
• Mask the taste
• Produce high surface area in the GIT, drugs are administered in a finely divided form

Question 4

Dosage forms?

Answer 4

Oral, ocular, topical and parenteral

• Liquid or semisolid
• parenteral suspension control rate of absorption
• Increase duration of action, vary particles size

Question 5

Suspensions used as?

Answer 5

Vaccines

Diagnostic tests

Question 6

Desired properties of suspensions?

Answer 6

Sufficiently homogenous
Settle slowly
Easily resuspended
Pour readily and evenly
Particle size constant even in undisturbed standing
Optimal viscosity

Question 7

Suspended particles?

Answer 7

Thermodynamicallly unstable

Van der Waals interactions

Question 8

Define flocculation

Answer 8

Process of forming flocs

• London and van der Waals + repulsion forces
• Settle rapidly
• easily resuspended
• Clears as flocs settle
• inaccurate dosing
• Unstable

Question 9

Define aggregation

Answer 9

Particles adhere to each other by stronger forces to form aggregates

Question 10

Define caking

Answer 10

Due to growth and fusion of crystals in the precipitates and produce a solid aggregate

Question 11

Deflocculated suspension?

Answer 11

Repulsive energy is too high

• Settle slowly
• Hard cake
• Difficult to re-suspend
• Cloudy
• Stable
• Uniform dosing

Question 12

Define ideal situation

Answer 12

Deflocculated suspension with a sufficiently high viscosity to prevent sedimentation

Question 13

Define controlled flocculation

Answer 13

• Balance flocculation
• Underflocculation: deflocculated
• Over flocculation is irreversible
• Particle size control and electrolytes to control zeta potential

Question 14

Define flocculating agents

Answer 14

Excipients used to achieve controlled flocculation

Question 15

Define electrolytes

Answer 15

Addition of inorganic electrolytes to an aqueous suspension can change the zeta potential

Question 16

Define Schulze-Hard Rule

Answer 16

The flocculating power of a chemical rises rapidly with its valance

Question 17

Define surfactants

Answer 17

Ionic surface active agents cause flocculation by neutralization of the charge
Nonionic surfactant adsorb on to more than one particle and form loose flocculated strucutre

Question 18

Define polymeric flocculating agents

Answer 18

Form gel like structures and become adsorbed on the surface of particles

Question 19

Suspending agents?

Answer 19

Usually negatively charged

Question 20

Positively charged suspened particle that is flocculated with an anionic electrolyte?

Answer 20

Use of negatively charged hydrocolloids may help avoid incompatibility
Use of oppositely charge flocculating agent may result in incompatibility

Question 21

Sedimentation of suspended particles

Answer 21

Particles size should be as small as possible
Increase the density of the liquid
- When equal to density of solid, sedimentation rate = 0
Increase viscosity of the dispersion medium

Question 22

F < 1

Answer 22

Final volume of sediment is smaller than the orignal

Question 23

F = 1

Answer 23

Final volume of sediment is equal to the original

Question 24

F > 1

Answer 24

Final volume of sediment is greater than the original

- loose and fluffy flocs

Question 25

Define degree of flocculation

Answer 25

Ration of sedimentation volume for flocculated suspension to the sedimentation volume of deflocculated suspension or as the ratio of ultimate sediment volumes
(U over O)

Question 26

Temperature of suspensions

Answer 26

Increase lead to under or over flocculation

• heated: energy of repulsion tends to decrease
• freezing and thawing: strong attraction and forms aggregates
• Size is inversely related to freezing rate
• Fluctuation can alter particle size and polymorphic form

Question 27

Excipients of suspensions

Answer 27

Adversely affect the stability o fa suspension

- Change reversal

Question 28

Dry powders for suspensions

Answer 28

Do not contain the vehicle

Add exactly the right amount of water