suspension

particle size

uniform=narrow particle size distribution

particle with the samilar density
as medium can afford having
more particle because the
sedimentation rate is slower

stable

differentiating factor in suspension

slow sedimentation rate
slow to settle

particle size

too small

slow to settle

will form cake

too large

fast to settle

easy to re-disperse

10 x increase in particle size
results in 100x increase in
sedimentation rate

WANT the particle size to
be as narrow as possible

particle density

Density of particle less
than medium (water)

float

Density of particle a
>> than medium

fast to settle

WANT particle density to be a
little but lower than medium

slow sedimentation rate for stability**

easy to re-disperse

the stokes equation cannot determine
if particle will readily re-disperse

easy consistent pour

vehicle viscosity

adjusted in accordance
to particle size and density
to minimize sedimentation
rate

adjusted via addition

suspending agent

thickening agent

thixotropy is a
good vehicle

high stress --> less viscous

easy to disperse

over time viscosity increases

slow to settle

vehicle

not heavily adjusted to
achieve good suspension

thixotropy is a good vehicle

under high stress become less viscous

easy to disperse

overtime viscosity increases

slow to settle

flocculation

loose structure when settle

FLOC

thus easily redistributed

Antiacid - are inorganic particle that are insoluble in water

antiimicrobial- unstable in solutions

when. liquid is required but
drug is not dissolve in liquid or
unstable in solution

suspension can improve the stability
of undissolved drug

dose flexibility

mask the tase

better dissolution and absorption than tabelts

slower dissolution and absorption than tablets

suspension

finely divided particles distributed somewhat uniformly throughout a vehicle in which the drug exhibits minimum solubility

Particles( clubs) surrounded by water molecule

drug molecule surrounded by drug molecule

will not dissolve

WILL eventually settle over time

cant see through

vehicle

dispensing medium

external liquid phase

drug

the dispered phase

internal phase

suspensiod

3 main type

oral

oral suspensionn better flexibility in
dosing than oral tablet

most common

externally applied

lotion

parenteral

most common insulin zinc suspension

liposomal doxorubicin

suspension limitation in the blood
is the particle size of the drug.

particle size can be determined by
light transmission through the suspension

small particle size = light passes through

large particle size = light does not passes through

must be low particle size == looks like solution

fastes growing

particle size

Colloidal

< 1micron

nanometer range

suspension/solution

typically do not settle under gravity b/c so
small that particle remain suspended

may look like solution

coarse

over 1 micron

settle under gravity

always a suspension

Wetting to create barrier

surfactants

cover particles and form a bridge
between the lipophilic particle and
the hydrophilic medium

amphiphilic

used to reduce interfacial tension

creating a barrier to avoid "caking"

prevent particles from
sticking to each other

too much

bad tase

dissolution of drug

Extemporaneous
compound

from solid--> suspension

less stable

process

dispersed particle are wetted---> paste

add remaining vehicles in parts while mixing

all suspension particle
WILL eventually settle

once particles settle can form a
hard cake that does not re-distribute
easily and is to be avoided

avoid formation of "cake"

made by additive

clays

interfere with other particle creating barrier
thus help support the floc structure once it forms

most common

cons: add volume

Suractants

prevents particle from sticking

done by wetting

adjusting pH and electrolytes

promote int interactions for particle
to repple and prevent from clumping forming cake

most sophisticated

promote loose settling

we cannot prevent settling
might as well control it

artificially form when
particle settle to re disperse

process to form "floc", a loose structure
due to particle settling very fast

weak particle particle forces

fast settling but "fluffy" ( loose structure) = Floc

easily redistributed

disadvantage

lack drug stability data

cause clumps floating around

I-clicker

A flocculated system settles very rapidly not allowing enough time for accurate dosing. what would you try first to fix

A)reduce particle size of disperse phase

we already have a flocculated system! change is particle size can affect the flocculated systemm

B) increase viscosity

flocculated solution is a very loose suspension thus increasing viscosity will allow the drug to settle in a slower rate. giving more time for accurate dosing

C) use homogenizer to better breakdown the drug particle

RUIN the flocculated suspension??

d) add a wetting agent

wetting agent is used to make a flocculated system