Kategóriák: Minden - density - solution - suspension - stability

a Patricia Nicolas 6 éve

1312

suspension

Suspensions are mixtures where particles are dispersed in a medium and can be classified based on their particle size. Particles over one micron tend to settle under gravity and are always considered suspensions, while colloidal particles, typically in the nanometer range, do not settle due to their small size.

suspension

suspension

settling

avoid formation of "cake"

I-clicker

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

d) add a wetting agent

wetting agent is used to make a flocculated system

C) use homogenizer to better breakdown the drug particle

RUIN the flocculated suspension??

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

A)reduce particle size of disperse phase

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

disadvantage

lack drug stability data

cause clumps floating around

promote loose settling

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

easily redistributed

we cannot prevent settling might as well control it

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

weak particle particle forces

artificially form when particle settle to re disperse

made by additive

adjusting pH and electrolytes

most sophisticated

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

Suractants

done by wetting

prevents particle from sticking

clays

cons: add volume

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

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

preparing

process
add remaining vehicles in parts while mixing
dispersed particle are wetted---> paste
Extemporaneous compound
less stable
from solid--> suspension
Wetting to create barrier
too much

dissolution of drug

bad tase

used to reduce interfacial tension

prevent particles from sticking to each other

creating a barrier to avoid "caking"

surfactants

amphiphilic

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

classification

coarse

always a suspension

settle under gravity

over 1 micron

Colloidal

may look like solution

suspension/solution

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

< 1micron

nanometer range

3 main type
parenteral

fastes growing

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

must be low particle size == looks like solution

particle size can be determined by light transmission through the suspension

large particle size = light does not passes through

small particle size = light passes through

liposomal doxorubicin

most common insulin zinc suspension

externally applied

lotion

oral

most common

oral suspensionn better flexibility in dosing than oral tablet

definition

drug
suspensiod
internal phase
the dispered phase
external liquid phase
dispensing medium
cant see through
will not dissolve

WILL eventually settle over time

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

drug molecule surrounded by drug molecule

Particles( clubs) surrounded by water molecule

Why

slower dissolution and absorption than tablets
better dissolution and absorption than tabelts
mask the tase
dose flexibility
when. liquid is required but drug is not dissolve in liquid or unstable in solution
suspension can improve the stability of undissolved drug

common use

antiimicrobial- unstable in solutions
Antiacid - are inorganic particle that are insoluble in water

good suspension

flocculation
loose structure when settle

thus easily redistributed

FLOC

vehicle
thixotropy is a good vehicle

overtime viscosity increases

under high stress become less viscous

not heavily adjusted to achieve good suspension
easy consistent pour
vehicle viscosity

thixotropy is a good vehicle

over time viscosity increases

high stress --> less viscous

easy to disperse

adjusted via addition

thickening agent

suspending agent

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

the stokes equation cannot determine if particle will readily re-disperse
slow sedimentation rate slow to settle
slow sedimentation rate for stability**
Sedimentation rate

particle density

WANT particle density to be a little but lower than medium

Density of particle a >> than medium

Density of particle less than medium (water)

float

WANT the particle size to be as narrow as possible

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

too large

easy to re-disperse

fast to settle

too small

will form cake

slow to settle

particle size
differentiating factor in suspension
stable
particle with the samilar density as medium can afford having more particle because the sedimentation rate is slower
uniform=narrow particle size distribution