Suspensions

Front 1

List 5 applications for suspensions:

Back 1

insoluble materials
unstable materials
taste masking
controlled release (microspheres, liposomes)
dermatological and cosmetic (liposomes, ointments)

Front 2

microspheres break open by _________, _______

Back 2

pH
hydrolysis

Front 3

name 4 routes of administration for suspensions:

Back 3

oral
external
injectable
inhalation

Front 4

give 2 examples of suspension products:

Back 4

antibiotics
antacids

Front 5

preparing suspensions takes work. To reduce the work of preparing suspensions, add ______

Back 5

surfactant

Front 6

to reduce delta G, decrease __________ by adding a surfactant

Back 6

interfacial tension (gamma)

Front 7

A (area of dispersed phase) is reduced at the ____

Back 7

secondary minimum

Front 8

when particles in a suspension settle, they can either

Back 8

cake or floculate

Front 9

flocculation: agglomerates form by _________ between particles at secondary minimum

Back 9

van der Waals attraction forces

Front 10

with suspensions, do we want aggregation at secondary minimum?

Back 10

yes!

Front 11

at the secondary minimum we get flocculation. Is it better to settle as flocculated particles than individually?

Back 11

yes!

Front 12

the degree of flocculation is controlled by:

Back 12

balance between attractive and electrostatic repulsive forces

Front 13

when Vt is high, particles _____ approach

Back 13

CAN'T

Front 14

when Vt is low, particles _______ approach

Back 14

CAN

Front 15

deflocculation: Vt is _______

Back 15

high

Front 16

flocculation: Vt is ________, but must be ______ enough to prevent aggregation at the primary minimum

Back 16

low
high

Front 17

Produce for me, the equation for Stokes Law:

Back 17

V = [2r^2 (P-Po)g]/9n

Front 18

_________ motion counteracts sedimentation

Back 18

Brownian

Front 19

if viscosity of continuous phase is high, then Brownian motion is _________

Back 19

negligible

Front 20

Density of the dispersed phase is almost always ______ than the continuous phase, hence ________

Back 20

greater
dispersed particles or aggregates settle

Front 21

Stokes Law is valid for free settling if:

Back 21

concentration is low (<1% w/v solid, interparticulate interaction is minimal)

Front 22

sedimentation of deflocculated suspension:
Vt is _____

Back 22

high

Front 23

sedimentation of flocculated suspension:
Vt is ____

Back 23

low

Front 24

sedimentation of deflocculated suspension:
particles sediment _______, r is ________

Back 24

slowly
small

Front 25

sedimentation of flocculated suspension:
particles sediment _____, r is _______

Back 25

rapidly
large

Front 26

sedimentation of deflocculated suspension:
forms ________ sediment

Back 26

close packed

Front 27

sedimentation of flocculated suspension:
forms _______ sediment

Back 27

loose

Front 28

sedimentation of deflocculated suspension:
RESULT:

Back 28

hard cake, difficult to redisperse

Front 29

sedimentation of flocculated suspension:
RESULT: _________

Back 29

no cake, easy to redisperse

Front 30

Formula for measurement of sedimentation?

Back 30

F=Hu/Ho

Hu = final volume of sediment
Ho = original volume of sediment

(really light, not volume)

Front 31

for defloculated suspension, F is _____

Back 31

small (<0.1)

Front 32

for flocculated suspension, F is ______

Back 32

large (0.25-1.0)

Front 33

4 ways of controlling flocculation:

Back 33

electrolytes, pH change, bridging flocculation, viscosity enhancers

Front 34

Controlled flocculation:
electrolyte:
all + charges = _____________
add e- for mix of + and - charges = _________
add more e- so you have basically all - charges= ___

Back 34

cake
flocculation
cake

Front 35

Controlled flocculation:
pH change:

Back 35

???????

Front 36

Controlled flocculation:
Bridging flocculation:
Polymers such as ______ cause flocculation by bridging at low concentration.

Back 36

xanthan gum

Front 37

Controlled flocculation:
Viscosity enhancers:
Add structured vehicle. Increase in viscosity of continuous phase decreases ______

Back 37

sedimentation of flocculated dispersed phase

Front 38

provide an example of a viscosity enhancer

Back 38

carboxymethyl cellulose
tragacanth
bentonite
lyophilic colloids

Front 39

viscosity enhancers are often _______ - shear thinning

Back 39

thixotropic

Front 40

Controlled flocculation:
Viscosity enhancers:
Can get incompatibilities between electrolytes and _____

Back 40

structured vehicles

Front 41

List 2 other problems associated with suspensions:

Back 41

crystal growth
changes in the polymorphic form of the drug

Front 42

Ostwald ripening during storage:

Back 42

change in size distribution

Front 43

smaller particles become

Back 43

smaller

Front 44

larger particles become

Back 44

larger

Front 45

Solution theory:
smaller particles: ____ for a particle to leave a surface due to higher surface energy

Back 45

easier

Front 46

Solution theory:
________ for a particle to join onto a lower surface energy (on a large particle)

Back 46

easier

Front 47

over time with Ostwald ripening, you just get all _______ particles, leading to a ______ in bioavailibility

Back 47

large
decrease

Front 48

name two types of controlled release suspensions:

Back 48

ion exchange resins
microspheres

Front 49

Ion exchange resins:
Positively charged drug is exchanged with Na+ since Na+ has greater affinity?

Back 49

???

Front 50

name two types of microspheres:

Back 50

micromatrix (drug in polymer matrix)
microcapsule (drug surrounded by polymer)

Front 51

Why is PLGA used for microspheres?

Back 51

no toxicity - the body can degrade PLGA by hydrolysis to lactic acid and glycolic acid.

Front 52

can microspheres be used for hydrophobic or hydrophilic drugs or both?

Back 52

both

Front 53

describe microsphere drug release over time:

Back 53

initial burst of drug that was on surface, lag time as matrix dissolves, then more drug

Front 54

give two reasons why the sub Q space is more predictable between people than IM

Back 54

less vascularization in skin than in muscle

less variability in skin than in muscle

Front 55

microsphere degredation rate is dependent on _____ and ______

Back 55

molecular weight (higher = slower release)

copolymer ratio

Front 56

Complex coacervation

Back 56

???????