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Lab Final - Suspensions
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disperse system definition
two phased liquid prep made of undissolved drug/immiscible liquid (dispersed phase) distributed in a vehicle (dispersion medium)
suspension definition
disperse system in which a finely divided solid is dispersed in a continuous phase of solid, liquid, or gas
particle size of single vs two phase
single phase
: <1 nm
two phase
: 10-50 μm
what is a suspension made of?
dispersed particle (drug)
liquid medium
excipients
suspension excipients
wetting agents
flocculating agent
viscosity enhancer/suspending agent
preservative (benzoic acid, sodium benzoate)
flavoring agent
when are wetting agents used in suspensions?
when the dispersed phase isn't easily penetrated by the vehicle (clumps or float)
what do wetting agents in suspensions do?
displace the air making the powder more penetrable by dispersion medium
examples of suspension wetting agents
alcohol
glycerin
other hygroscopic liquids
what happens in unstable suspensions
dispersed particles form aggregates
aggregates settle by dispersion
cakes form that are difficult to resuspend
stokes law gives you what?
the settling velocity of a smooth, rigid sphere in a viscous fluid - sedimentation rate
what factors affect the sedimentation rate?
size of the particle (proportional to)
density diff between the particle and liquid (proportional to)
viscosity of the liquid (inversely proportional)
when is the sedimentation rate zero?
when the density of the particle is equal to the density of the liquid
what do flocculating agents do?
enhance particle dispersability
negate the surface charge on the suspended particles
allows the formation of loose networks of particles called "floccs/floccules" - easily re-dispersed by shaking
examples of flocculating agents
clay
surfactants
types of viscosity enhancers/suspending agents
natural hydrocolloids
semisynthetic hydrocolloids
synthetic hydrocolloids
clays
examples of natural hydrocolloids used as a viscosity enhancer/suspending agent
acacia
tragacanth
alginic acid
carrageenana
locust bean gum
guar gum
gelatin
examples of semisynthetic hydrocolloids used as a viscosity enhancer/suspending agent
methylcellulose
sodium carboxymethylcellulose
example of synthetic hydrocolloid used as a viscosity enhancer/suspending agent
carbopol
examples of clay used as viscosity enhancer/suspending agent
bentonite
veegum
what is a prednisolone/sulfacetamide suspension for?
treating inflammation of eyes and eyelids when infection or risk of infection is present
anitbacterial and corticosteroid combo
Author
jcu1
ID
212656
Card Set
Lab Final - Suspensions
Description
Lab Final
Updated
2013-04-10T16:30:39Z
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