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Compounding Exam 2 > Suspensions Part 2 > Flashcards

Suspensions Part 2 Flashcards

1
Q

explain what flocs/flocculated suspensions are

A

particles are weakly bound together (called flocs) when the forces of attraction are just slightly greater than the repulsive forces

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2
Q

true or false

flocculated suspensions rapidly undergo sedimentation

A

true

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3
Q

are flocculated suspensions readily re-suspended?

A

YES

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4
Q

flocculated suspensions have a______ sedimentation volume

A

large

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5
Q

what is the appearance of the supernatant in flocculated suspensions

A

supernatant = region on top of the suspended particles

will be CLEAR in flocculated suspensions bc even the smallest particles are involved in the flocs — will not be cloudy

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6
Q

_____ suspensions are also known as aggregated suspensions

A

DEflocculated

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7
Q

do deflocculated suspensions settle fast or slow?

A

slow

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8
Q

explain why and how deflocculated suspensions are not desirable

A

they will form a sediment (CAKE) eventually

bc the larger particles will settle faster and the small ones will fill in the voids between the large particles. thus, the lower most particles will be pressed together by the weight of the ones above

THIS IS DIFFICULT OR IMPOSSIBLE TO RESUSPEND ONCE CAKED

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9
Q

true or false

deflocculated suspensions initially have a pleasant appearance

A

TRUE
they will remain cloudy for a while after shaking

BUT —– will eventually form a cake

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10
Q

what is actually an advantage of deflocculated suspensions?

A

uniform dosing can be achieved – but only EARLY before the cake forms
this is bc the sedimentation occurs SLOWLY

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11
Q

true or false

deflocculated suspensions have poor physical stability/quality

A

true

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12
Q

in deflocculated/aggregated suspensions, explain the relationship between attractive and repulsive forces

A

the internal phase attraction is MUCH greater than repulsion - will form a cake

(however for defloc the attractive forces are just slightly greater than repulsive)

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13
Q

suspending agents can also be called….

A

viscosity inducing agents

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14
Q

how do suspending agents work to increase viscosity of the continuous medium

A

they form a film around the particles and decrease their attraction to each oter

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15
Q

name 5 suspending agents

explain structurally what they usually are

A

alginates
CMC
xanthan gum
tragacanth
acacia

long chain molecules or natural or synthetic powder gums

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16
Q

name 2 non ionic surfactants and what surfactants do in suspensions

A

span and tween

decrease the interfacial tension between the particles and the liquid

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17
Q

function of wetting agents in suspensions and name 2

A

glycerin and propylene glycol

to enhance the penetration of the vehicle into the drug particles. POWDER MUST BE WETTED to be formulated as suspension

18
Q

**note - she may ask if something is a solution or suspension just from looking at ingredeitns - know what to look for

A

ie - suspending agent/wetting agent/surfactant for suspension

19
Q

function of buffers in suspensions

what is normal pH

A

to resist pH changes and maintain the pH of the formulation

7.4-8.4

20
Q

name 4 things that can be used as buffers in suspensions

A

carbonates
citrates
gluconates
phosphate salts

21
Q

why are osmotic agents added to suspensions?
which particular suspensions are they usually added to?

name 4

A

opthalmic and injectable suspensions

to make osmotic pressure comparable to body fluids (isotonic)

dextrose, mannitol, sorbitol, glycerol

22
Q

why are humectants added to suspensions and name 2

A

propylene glycol and glycerol

added to ASBORB MOISTURE to prevent the API from degrading

23
Q

in solutions, co solvents are added to improve solubility of the drug

but what are cosolvents used for in the case of suspensions?

A

to enhance the viscosity of the dispersion medium – bc they have a high viscosity in themselves

glycerin, PPG, sorbitol

24
Q

which preservatives are only effective at a low pH (less than 4) and are thus not used a lot for suspensions bc the ideal pH is 7.4-8.4?

A

benzoic acid and benzoic acid salts

25
Q

why are parabens used in pairs as preservatives?

A

bc they show synergy

26
Q

why are parabens very commonly used in suspensions?

A

bc effective at ph 4-8

27
Q

**name the concentration of alcohol needed to preserve suspensions in:

-acidic media
-neutral/alkaline media

A

acidic - 15% alcohol
neutral/alkaline - 18% alcohol

28
Q

combo of ___% methyl paraben and ___% propyl paraben is commonly used as preservative

A

0.18% methylparaben
0.02% propylparaben

so around .2% all together

29
Q

explain the ideal packaging of suspensions

A

TIGHT CONTAINERS with big enough opening to pour viscous liquid

enough space to shake well

SHAKE WELL BEFORE USE STICKER

label should indicate if internal or external use

30
Q

which USP chapter is stability considerations

A

USP1191

31
Q

3 major signs of instability of suspensions

A

-cake
-ostwald ripening (large particles - excessive crystak growth)
-microbial contamination bc of free water

32
Q

when compounding a suspension, if any of the solids are determined to to be soluble in the amount of vehicle prescribed, what should you do?
**

A

DO NOT WANT EVERYTHING TO DISSOLVE

just dissolve in PART OF the vehicle

33
Q

**in compounding suspensions, what should be done with the INSOLUBLE powders

A

be placed in a mortar and triturated according to GEOMETRIC DILUTION

34
Q

why is trituration necessary for suspensions but not solutions

A

solutions will dissolve anyway

35
Q

***when wetting the insoluble powders that have been triturated according to geometric dilution, what should be done nect?

A

add just enough of an appropriate wetting agent (ie - glycerin) to make a THICK, SMOOTH PASTE – called a NUCLEUS

this removes air pockets

36
Q

*once the powder has been wetted, what is done nect?

A

the vehicle is added in portions with suspending agent

thorough mixing after each addition

add most of the vehicle amount while the mixture is still in the mortar

then transfer to conical graduate and rinse mortar with remaining vehicle

QS, transfer to prescription bottle

SHAKE WELL BEFORE USE

37
Q

when compounding a suspension, you notice that 1 of the ingredients is soluble in water

what do you do?

A

dissolve it in a PORTION of the water

38
Q

whenever a liquid formulation calls for the use of a tablet or capsule, prepare it as a ________

why?

A

SUSPENSION

bc even if the API is soluble in water, there are so many other ingredients that are not

39
Q

based on stokes, rate of sedimentation decreases if the viscosity of the external phase ________

A

increases

40
Q

based on stokes equation, the rate of sedimentation decreases if the particle size of the internal pahse _________

A

decreases

41
Q
A

Compounding Exam 2 (9 decks)

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