internal and external suspensions

Question 1

what is a suspension?

Answer 1

a mixture of 2 or more components resulting in a 2 phase system

Question 2

what are some reasons for using suspensions?

Answer 2

poorly soluble drugs can be made into liquids, Unpleasant taste of drug can be masked by making them insoluble and suspending them in liquid
Drugs susceptible to hydrolysis can be made insoluble or suspended in oil
To deliver drug is a finely divided form with a large surface area

Question 3

what are some formulations of suspensions?

Answer 3

oral suspension, drops/sprays, lotions, shampoos, aerosols, rectal/vaginal, injections

Question 4

what is more common, diffusible solids or indiffusible solids?

Answer 4

indiffusible solids, they form clumps in the liquid

Question 5

what is the desirable movement of particles in a suspension

Answer 5

brownian movement- random movement and collision of particles
diffusion/osmosis - high conc to low conc

Question 6

what are the undesirable movements of particles in a suspension

Answer 6

sedimentation - stokes law of sedimentation velocity

-Flocculation – electro-static charges increase as particles get closer and can result in coagulation

Question 7

how can you control movement of particles?

Answer 7

reduce particle size - increased diffusion and decreased sedimentation
-increase viscosity of vehicle - decreased diffusion and sedimentation

Question 8

what are the ideal properties of a suspension?

Answer 8

slow sedimentation, easily re-dispersed, acceptable viscosity, stable to changes in temperature and pH.
This is difficult to achieve and so often there is a compromise balancing different systems

Question 9

what do density modifiers do?

Answer 9

prevent sedimentation

Question 10

what do suspending agents/thickeners do?

Answer 10

prevent sedimentation

Question 11

what do wetting agents do?

Answer 11

reduce interfacial tension and clumping

Question 12

what are the advantages of oral suspensions?

Answer 12

easier to swallow, fast absorption from GIT, deliver drug in a finely divided form with high surface area, taste of drug is not as noticeable as solutions therefore its more palatable, can be used for insoluble drugs and can prevent hydrolysis

Question 13

what are the disadvantages of oral suspensions?

Answer 13

not convenient for the patient, less stable than solutions, accuracy of dosing, can separate and sediment, must shake to re-disperse and reduce the viscosity of the suspending agent, difficult to manufacture