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Dosage II > Suspensions > Flashcards

Suspensions Flashcards

1
Q

Suspensions

A

-solid particles dispersed in a liquid phase in which they are not soluble

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2
Q

Peptobismol example

A

-active ingredient: bismuth subsalicylate
-suspension of insoluble salt of salicylic acid linked to bismuth cation

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3
Q

suspensions vs solutions

A

-solubility
-chemical stability (0 vs1st order)
-palatability (taste)

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4
Q

suspesions vs tablets

A

-flexibility of dose
-ease of swallowing
-dissolution rate

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5
Q

Components of Suspension

A

-active ingredient (solid particles)
-vehicle
-buffer
-preservative
-flocculating agent
-structured vehicle system
-wetting agent
-antifoaming
-flavor and sweetener

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6
Q

Desirable properties of Suspensions

A

-suspended material should not settle rapidly
-particles that settle must not form a hard cake and readily be redispersed when shaken
-easy to admin
-particle size remains constant in storage

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7
Q

Viscosity of suspension

A

-should not flow thru syringe needle
-fluid enough to spread over affected area

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8
Q

Settling equations

A

-Stokes Law

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9
Q

Particle size

A

-micropulverization (10-50mcm)
-fluid energy grinding (10mcm)
-spray drying (5 mcm)

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10
Q

Micropulverization

A

-10-50mcm
-high speed attrition or impact mills

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11
Q

fluid energy grinding

A

-less than 10 mcm
-jet milling, micronizing
-shearing action of high-velocity compressed airstreams on the particles in a confined space

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12
Q

Spray drying

A

-5mcm
-spray dryer: cone-shaped apparatus into which a solution of drug is sprayed and rapidly dried by current of warm, dry air circulating in the cone

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13
Q

Suspension Formulation Designs

A

-dispersed phase (solid particles)
-dispersion medium

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14
Q

Types of suspension

A

-dispersed suspension
-flocculated suspension
-structured vehicle system

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15
Q

Thermodynamic stability

A

slide 13

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16
Q

Interparticle forces

A

-van der Waals ATTRACTIVE
-hydration REPULSIVE
-electrostatic REPULSIVE
-steric REPULSIVE

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17
Q

van der waals attractive force

A

-operates at moderate distance from the surface but becomes very strong close to the surface
-NOT affected by formulation factors

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18
Q

Hydration REPULSIVE force

A

-due to absorbed water molecules at surface of particle
-NOT affected by formulation factors

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19
Q

Electrostatic repulsive force

A

-due to surface charge on the particles
-may be affected by formulation

20
Q

Steric REPULSIVE force

A

-due to an absorbed layer of neutral polymer at surface of a particle
-may be affected by formulation

21
Q

forces NOT affected by formulation factors

A

-van der waals ATTRACTICE
-hydration REPULSIVE

22
Q

forces that might be affected by formulation

A

-electrostatic REPULSIVE force
-steric REPULSIVE force

23
Q

Net effect of interparticle forces

A

slifde 15?

24
Q

Dispersed suspension

A

-make REPULSIVE forces dominant
-particles repel each other
-no aggregation

25
Q

Problems with dispersed suspensions

A

-particles settle as individual particles
-leads to dense compact sediment (cake)

26
Q

Controlled Flocculation

A

-repulsive and attractive forces are in BALANCE
-particles attracted to each other at the secondary minimum to form aggregates (aka floccules)
-settles as a sediment with a high volume
-type of sediment is easy to redisperse

27
Q

slide 18

A

slide 18

28
Q

choice of Flocculating agents

A

-depend on type of drug and type of product desired

29
Q

Flocculating agents

A

-clay (diluted bentonite magma)
-change pH
-Electrolytes
-non-ionic or ionic surface-active agents

30
Q

Clay (diluted bentonite magma)

A

-flocculating agent
-oral suspensions

31
Q

changing pH of suspension

A

-to region of minimum drug solubility
-flocculating agent
-parenteral solution

32
Q

Electrolytes

A

-flocculating agents
-reduce the electrical barrier between the particles

33
Q

Why dont we want suspension to settle too rapidly

A

-hinders accurate measurement of dosage
-esthetically not good

34
Q

structured vehicle

A

-thicjen the dispersion medium to help suspend particles
-polymer or clay
-should not interfere w availability of drug
-should not make the suspension too viscous to agitate or to pour

35
Q

Rheology

A

-study of flow characteristics
-shear rate (dv/dr)
-shear stress (F)

36
Q

Shear rate (dv/dr)

A

-difference of velocity (dv) between two planes of liquid separated by a distance (dr)

37
Q

Shear Stress (F)

A

-force per unit (F’/A) required to bring about flow

38
Q

Newtonian flow

A

slide 16

39
Q

Non-newtonian flow

A

-plastic
-pseudoplastic
-dilatant

40
Q

Plastic non-newtonian flow

A

-typical of flocculated suspensions
-f (yield value)

41
Q

f (yield value)

A

-threshhold of shear stress necessary to initiate flow
-shear-thinning

42
Q

Psuedoplastic non-newtonian flow

A

-typical of polymer solutions such as methyl cellulose, polyvinyl alcohol, sodium carboxymethylcellulose, xanthan
-shear-thinning

43
Q

Dilatant non-newtonian flow

A

-exhibited by suspension having a high solids content
-shear-thickening

44
Q

Thixotropy

A

-

45
Q

got like 10. more slides

A

Dosage II (20 decks)

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