Suspensions

Question 1

suspensions are ____ phase systems:

Answer 1

2 phase

finely divided solid dispersed in a liquid medium

Question 2

a pharmaceutical suspension is a ____ dispersion in which the internal phase is dispersed uniformly throughout the external phase

Answer 2

COARSE

solute is greater than 1 micron

(usually in compounding it’s around 400microns, and for commercial suspension it’s 3 microns)

Question 3

how is the internal phase of insoluble solid particles maintained uniformly throughout the suspending vehicle??

Answer 3

1 or more suspending agents

Question 4

true or false

suspensions are better at overcoming disagreeable taste than solutions

Answer 4

TRUE

Question 5

which has faster rate of absorption - suspension or solution?

Answer 5

SOLUTION

Question 6

True or false

some drugs are chemically unstable in solution but stable when suspended

Answer 6

TRUE

Question 7

true or false

suspensions are only given by oral route

Answer 7

FALSE

can be externally applied or parenteral (ie - IM injection)

Question 8

differentiate between dilute vs concentrated suspensions

Answer 8

dilute - 2-10% w/v of solid

concentrated - 50%w/v solid

Question 9

how can suspensions be classified based on the proportion of solid particles

Answer 9

dilute or concentrated suspensions

Question 10

3 ways suspensions can be classified by the SIZE of the solid particles

Answer 10

colloidal suspension (less than 1 micron)

coarse suspension (for compounded - 400 microns, for commercial ~3 microns)

nano suspension - 100-200nm

Question 11

how can suspensions be classified based on the electro-kinetic nature of the particles

Answer 11

flocculated and deflocculated

Question 12

name the 2 forms that suspensions are available in

Answer 12

ready to use suspensions and dry powder for suspension

Question 13

how can you tell if a suspension is ready to use or a dry powder for suspension just by looking at the label?

Answer 13

“FOR ORAL SUSPENSION” indicates it is a dry powder for suspension

Question 14

as recap, alcohol limits by age

Answer 14

less than 6 yrs old = <0.5%

6-12 yrs = <5%

children greater than 12yrs = <10%

Question 15

true or false

essences and spirits cannot be given to pediatrics

Answer 15

TRUE

Question 16

3 reasons why alcohol content limited for pediatrics

Answer 16

can alter liver function

cause gastric irritation

affect neurological depression

Question 17

true or false

suspensions are not thermodynamically stable

Answer 17

TRUE

this is a disadvantage

bc of physical instability, they tend to settle over time and have lack of uniformity when dosing - MUST SHAKE WELL BEFORE USE

Question 18

which are more CHEMICALLY stable - drugs in solution or drugs in suspension?

Answer 18

suspension

Question 19

true or false

***drugs in suspension exhibit faster rate of absorption than many other dosage forms

Answer 19

TRUE

Question 20

***rank the following by rate of absorption

capsule
coated tablet
suspension
compressed tablet
solution

Answer 20

FASTEST - solution
suspension
capsule
compressed tablet
SLOWEST - coated tablet

Question 21

true or false

suspensions can mask the bad taste of a drug

Answer 21

TRUE

Question 22

true or false

suspensions cannot be given as IM injections of depot therapy

Answer 22

FALSE - they can

Question 23

true or false

a disadvantage of suspensions is that they are difficult to formulate

Answer 23

TRUE

bc they need wetting agent, suspending agent, etc

Question 24

true or false

uniform and accurate dosing is easy to achieve with suspensions, and this is an advantage

Answer 24

FALSE

hard to achieve (UNLESS they are packed in unit dosing)

Question 25

a disadvantage of suspensions is that they may be unpleasant to patients why?

Answer 25

bc of the texture

Question 26

true or false suspensions are bulky and hard to handle and transport

Answer 26

true

Question 27

_____ viscosity for suspensions enhances physical stability how?

Answer 27

HIGH bc the particles settle slower

Question 28

name the 2 types of flow

Answer 28

newtonian flow and non-newtonian flow

Question 29

name the types of newtonian/non-newtonian fluids

Answer 29

newtonian - water/ethanol/olive oil/etc non-newtonian - plastic flow/pseudoplastic flow/dilatant flow

Question 30

most pharmaceutical fluids (IE - suspensions, emulsions, and gels) exhibit what flow

Answer 30

NONNEWTONIAN FLOW - PSEUDOPLASTIC

Question 31

differentiate between what newtonian vs non-newtonian flow means

Answer 31

for NEWTONIAN fluids, viscosity will NOT change but will move when you heat it for NONNEWTONIAN FLUIDS - the viscosity varies with the rate of sheer

Question 32

"shear stress-dependent flow" newtonian or non-newtonian

Answer 32

NON NEWTONIAN

Question 33

Bingham flow is also known as...

Answer 33

plastic flow

Question 34

explain how plastic (bingham) flow works

Answer 34

the bingham bodies do NOT begin to flow until a shearing stress (corresponding to the YIELD VALUE) has been exceeded -have to shake well enough in order for flow (movement) to occur

Question 35

what are bingham bodies vs liquids

Answer 35

substances that have a YIELD VALUE as solids yield value must be met before flow liquids will flow at the smallest yielding stress and have NO yield value

Question 36

why does a "yield value" exist for plastic flow

Answer 36

bc of the van der waals forces holding the flocculated particles together -these forces must be broken down before flow can occur!

Question 37

the more flocculated the suspension, the _____ the yield value

Answer 37

HIGHER

Question 38

true or false if a product has a very high yield value, it will run easily

Answer 38

FALSE - low yield value will run easily

Question 39

what flow is "shear-thinning system"

Answer 39

pseudoplastic flow

Question 40

explain what pseudoplastic flow is is it desired?

Answer 40

YES - ideal flocculated suspension exhibits pseudoplastic flow as you give more and more shearing stress, the slope increases and the molecules move faster and faster until it becomes thin and runny. the long chain molecules will line up in 1 direction to move really fast

Question 41

______ behavior is important for topical products why?

Answer 41

pseudoplastic when the viscosity decreases with stress, makes it easier to squeeze the product out of the container and to rub the product on large area of skin

Question 42

in pseudoplastic flow, the long chain molecules (when put under stress) line up in what direction?

Answer 42

the direction of the flow makes thin and runnt

Question 43

what kind of flow is "shear-thickening systems" is it desired?

Answer 43

dilatant flow NOT ideal for suspensions. it's the opposite of pseudoplastic flow thickens and moves LESS as you apply more and more stress

Question 44

_______ pharmaceutical materials may solidify under the conditions of high shear, damaging the equipment

Answer 44

DILATANT ie - pushing IM injection - the suspension will thicken with the stress and not come out

Question 45

when sheared, dilatant suspensions ______ in volume

Answer 45

increase

Question 46

when the stress on a solidified dilatant system is REMOVED, what happens?

Answer 46

the suspension returns to its original state of fluidity

Question 47

what is Ostwald ripening

Answer 47

suspensions that have a HIGH PERCENTAGE of dispersed solids will have an increase in resistance to flow as the rate of shear increases -- WILL GET BIGGER true for dilatant suspension

Question 48

example of a household product that exhibits dilatant/shear-thickening flow

Answer 48

whipped cream

Question 49

explain how with increasing rate of shear, whipped cream begins to thicken and get larger (dilatant flow)

Answer 49

the insoluble proteins/globules will introduce AIR POCKETS

Question 50

Explain what thixotropy is

Answer 50

when you don't touch it, it will become thick and viscous -- a gel like semisolid however, once you shake, it will flow and become runny to be easy to pour. when you let it sit again, it will regain viscosity but TAKES TIME TO REGAIN!!!!! this is time-dependent thixotropy. don't want it to gain viscosity too quickly

Question 51

name 2 routes of administration that thixotropic suspensions and emulsions can be used for and why

Answer 51

IM injections and nasal sprays IM injections - when the drug passes the needle, it will break down in thickness and produce a DEPOT at the muscle, resulting in sustained release action nasal spray (ie - nasonex) - SHAKE WELL BEFORE USE. this will allow it to flow more freely to spray. when it thickens in the nasal cavity, it wont leak out and is able to stay there longer

Question 52

what is the name of the law involved with the sedimentation of suspended particles

Answer 52

STOKES LAW

Question 53

to DELAY sedimentation according to stokes law, what should the particle size be?

Answer 53

as small as possible

Question 54

as density of the liquid medium INCREASES, sedimentation rate _____

Answer 54

decreases

Question 55

when is the sedimentation rate zero?

Answer 55

when the density of the medium is equal to the density of the solid

Question 56

as the viscosity of the dispersion medium decreases, what happens to sedimentation rate?

Answer 56

it increases

Question 57

true or false it is desirable for suspensions to have very rapid sedimentation

Answer 57

FALSE

Question 58

true or false trituration is not necessary for suspensions

Answer 58

FALSE - IT IS we want the particle size to be as small as possible to limit the rate of sedimentation optional for SOLUTIONS bc it will dissolve either way

Question 59

"particles should be easily redispersed on gentle shaking and regain viscosity SLOWLY"

Answer 59

thixotropy

Question 60

throughout long periods of undisturbed standing of suspensions, what should happen to the particle size

Answer 60

should remain CONSTANT

Question 61

true or false it is desirable to have no grittiness in pharmaceutical suspensions

Answer 61

TRUE also why we must triturate

Question 62

it's important for suspensions to have a balance between ___ and ____

Answer 62

stability vs pourability should pour readily and evenly, but not be too watery

Question 63

_____ suspensions should be sterilizable

Answer 63

parenteral/ophthalmic

Question 64

which have longer (higher) shelf lives and WHY - commercial suspensions or compounded suspensions?

Answer 64

commercial suspensions because they have a much smaller particle size than compounded suspensions and are thus more stable