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Pharmacy Practice Lab II > Lab 3 > Flashcards

Lab 3 Flashcards

1
Q

true or false

drugs insoluble in water cannot be formulated as aqueous solutions

A

TRUE

in these cases, they may be formulated as SUSPENSIONS

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2
Q

give the USP definition of suspensions

A

liquid preparations that consist of solid particles dispersed throughout a liquid phase (in which these particles are not soluble)

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3
Q

the formulation of drugs as suspensions for oral administration is a convenient way to administer what kind of drugs?

A

insoluble or sparingly soluble drugs

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4
Q

besides being a good way to administer insoluble/sparingly soluble drugs, why else are suspensions useful?

A

useful to mask taste and to control absorption rate of the drug

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5
Q

true or false

formulating suspensions can be challenging

A

true

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6
Q

what are indiffusible suspensions?

A

they contain insoluble powders that

-do not disperse evenly throughout the liquid vehicle long enough to give an accurate dose

-the insoluble powders form a cake (non dispersible sediment) that may not disperse easily when shaken

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7
Q

when the solids in a suspension settle too fast….

A

the dose measured is not consistent

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8
Q

if the solid contents of a suspension form a solid cake at the bottom which does not disperse with brief shaking……

A

the drug is not present, or is in less concentration in the dose measured

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9
Q

___________ of a suspension is a critical requirement of all suspensions

A

redispersability

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10
Q

caking of a suspension is even more severe when……

A

a suspension is stored over long periods

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11
Q

name the 5 criteria for a well-formulated suspension

A
  1. Suspended material should not settle rapidly
  2. Settled solids should be easily redispersible
  3. Settled solids should not form a hard cake
  4. Suspension must be easily pourable
  5. Suspension must have the aesthetic requirements of the dosage form
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12
Q

one of the 5 criteria for a well formulated suspension is that the suspended material should not settle rapidly.

why is this?

A

when the solids settle too quickly, it doesn’t allow enough time for accurate dose measurement

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13
Q

1 of the 5 criteria for a well formulated suspension is that settled solids should be easily redispersible.

why is this?

A

when the solids redisperse quickly with brief shaking, the concentration is uniform in every dose poured

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14
Q

what is another word for solids that have settled

A

sediment

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15
Q

1 of the 5 criteria for a well formulated suspension is that the sediment should not form a hard cake

why is this?

A

if a hard cake is formed, the drug cannot be redispersed upon shaking.
this results in dosing errors.

the patient will receive LESS dose than what is prescribed

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16
Q

if a hard cake is formed, the patient will receive ____ dose than what was prescribed

(less or more)

A

less

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17
Q

1 of the 5 criteria for a well formulated suspension is that the suspension must be easily pourable.

why is this?

A

if the suspension is too thick, the dose cannot be measured accurately

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18
Q

what 2 factors affect the pourability of the suspension?

A

-the amount of powder in the formulation

-the concentration of the viscosity agents

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19
Q

to obtain an easily pourable suspension, _____ and ____ must be adjusted appropriately

A

the concentration of the active drug (powder) and viscosity should be adjusted appropriately

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20
Q

1 of the 5 requirements for a well formulated suspension is that the suspension must have the aesthetic requirements of the dosage form.

explain this further

A

-the suspension should not support microbial growth

-the drug powder particles must be uniform in size to give a homogeneous appearance and dose accuracy

-must be palatable and appealing

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21
Q

give 2 reasons why the drug powder particles should be uniform in size

A

-to give a homogeneous appearance

-for dose accuracy

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22
Q

name the requirements for injectable suspensions in particular

A

must be STERILE and not cause damage at the injection site

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23
Q

true or false

sedimentation rate is affected by one factor

A

FALSE – affected by multiple factors and its estimation is often complex

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24
Q

how can the rate of sedimentation be estimated?

A

by using stokes equation (Law)

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25
Q

When simply put, the Stokes equation states that sedimentation rate can be manipulated by what 3 things?

A

-reducing the particle size
-increasing the viscosity
-increasing the density of the external phase (VEHICLE)

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26
Q

what kind of suspensions may NOT ADHERE to Stokes Law?

A

suspensions that have very high concentrations of dispersed particles

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27
Q

“the insoluble solid powder must be reduced to small particles and dispersed in a _______ medium”

A

continuous

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28
Q

_____, _____, and ______ are generally used to reduce particle size

A

comminution, pulverization, and levigation

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29
Q

to ___ suspensions, it is necessary to add a suspending and/or gelling agent to retard (slow) the settling of the particles

A

STABILIZE

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30
Q

to stabilize suspensions, it is necessary to add a _____ agent to retard the settling of the particles

A

suspending agent and/or gelling agent

31
Q

what is the function of a suspending/gelling agent

A

to stabilize suspensions to slow (retard) the settling of particles

32
Q

substances added to increase the viscosity of the suspension are known as…..

A

viscosity enhancers

33
Q

true or false

viscosity enhancers are useful to prevent the settling of insoluble particles

A

true

34
Q

name 4 natural viscosity enhancers

A

acacia
tragacanth
gelatin
bentonite

35
Q

name 2 semisynthetic viscosity enhancers

A

methylcellulose
CMC (sodium carboxymethyl cellulose)

36
Q

according to the stokes law, increasing ____ and decreasing _____ promotes suspension stability through the prevention of sedimentation

A

increasing viscosity and decreasing particle size

37
Q

what is the ultimate aim of flocculation?

A

to control the aggregation, so that the aggregates formed are loosely bound and easily redispersible

38
Q

what are flocs

A

another word for aggregates. floculation aims to have lossely bound flocs so they are easily redispersible

39
Q

flocculation is a process related to…..

A

the formation of loose fluffy aggregates of suspended particles

40
Q

aggregated are called _____

A

flocs or floccules

41
Q

explain how flocculation can be accomplished

A

using charged molecules (polymers, electrolytes, clays) in their effective concentrations

the charged molecule must have an OPPOSITE CHARGE to the insoluble drug

the insoluble drug particles adhere to each other in suspension due to the opposite charge, but on storage they settle down as FLOCS, which produces loose, voluminous sediments containing large amounts of trapped liquid suspension medium

can be easily redispersed

42
Q

flocculation is useful in suspensions to prevent ____

A

caking

43
Q

in highly flocculated suspensions, what happens?

A

the particles of the suspension settle too rapidly, leading to physical instability and lack of dose uniformity

44
Q

true or false

flocculating agents tend to decrease the rate of settling

A

FALSE – increase

45
Q

a useful technique to obtain uniform redistribution is called……….

A

controlled flocculation

46
Q

what is a convenient parameter to assess flocculation?

A

F (sedimentation volume)

47
Q

define F

A

the ratio between sediment volume and the original volume

a parameter used to assess flocculation

48
Q

besides sedimentation volume (F), flocculation also depends on what 2 other things?

A

the concentration and size of the insoluble particles

49
Q

_____ are used in oral suspensions as flocculating agents

A

clays (bentonite)

50
Q

____ and ____ are used as flocculating agents in several different dosage forms

A

ionic and non ionic surfactants

51
Q

for parenteral suspensions, how can flocculation be achieved?

A

by modifying pH and through the addition of electrolytes

52
Q

what induces the flocculation of weakly charged drugs?

A

low concentrations (0.01-0.1%) of neutral electrolytes (NaCl or KCl)

53
Q

for HIGHLY charged drugs, how is the flocculating agent chosen?

A

based on the type of charge of the suspended particle

54
Q

the flocculating power increases with……

A

the valence of the ions

55
Q

name an anionic flocculating agent.

it is useful for the flocculation of what kind of particles?

A

potassium dihydrogen phosphate

useful for flocculating positively charged (cationic) particles

56
Q

the particles of bismuth subnitrate are _____– charged originally

A

POSITIVELY

57
Q

after the addition of potassium dihydrogen phosphate to a bismuth subnitrate solution, what happens?

A

the charge is neutralized

58
Q

the concentration and choice of a flocculating agent depends on the characteristics of what 2 things?

A

the drug and the formulation

59
Q

deflocculating agents tend to ____ the tendency to cake

A

increase

60
Q

when the repulsion energy between the insoluble particles is high, the collision between the same charged particles is ____

A

opposed – they repel each other and remain as discrete, single particles and the system remains deflocculated

61
Q

over a period of time, what will happen to deflocculated particles?

A

they will begin to settle very slowly in stages

particles lowest in the sediment are gradually pressed together by the ones above to ultimately form a dense sediment

62
Q

in extensively deflocculated suspensions, what can you say about the sediment particles?

A

the remain strongly attracted to each other and pack to produce compact, dense solid layers (cake) which is significantly more difficult to resuspend

63
Q

bismuth sibnitrate is positively charges in what conditions?

A

weakly alkaline (basic), neutral, and acid conditions

64
Q

bentonite has a ____ charged surface

A

negatively

65
Q

in suspensions containing bentonite and bismuth subnitrate, what happens?

A

the negative and positive charges on the surface of bentonite and bismuth subnitrate come together to form flocs

the charges on the outer surface of the floc are the same so the flocs repel each other

this prevents tight aggregation and cake formation.

these flocs can be EASILY REDISPERSED

66
Q

what is potassium dihydrogen phsophate used as?

A

an anionic flocculating agent

67
Q

in deflocculated suspensions, the particles settle fast or slowly?

A

slowly

68
Q

in which suspension do the particles form loose aggregates and are easily redispersable? (flocculated or deflocculated)

A

flocculated

deflocculated suspensions form hard cakes

69
Q

in which suspension is the electron potential between the particles HIGH?

(deflocculated or flocculated)

A

deflocculated

70
Q

in which suspension are the particles aggregated?
(flocculated or deflocculated)

A

flocculated

71
Q

in which suspension do the particles behave like neutral groups? in which suspension do the particles behave like charged particles?

(flocculated or deflocculated)

A

neutral groups - flocculated

charged particles – deflocculated

72
Q

viscosifying agents keep the particles ___ while flocculating agents keep the particles ____

A

visocifying agents keep the particles suspended while flocculating agents keep the particles aggregatd

73
Q

what is the function of methylcellulose

A

viscosifier

74
Q
A

Pharmacy Practice Lab II (12 decks)

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