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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)
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
- 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
- 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
types of viscosity enhancers/suspending agents
- natural hydrocolloids
- semisynthetic hydrocolloids
- synthetic hydrocolloids
examples of natural hydrocolloids used as a viscosity enhancer/suspending agent
- alginic acid
- locust bean gum
- guar gum
examples of semisynthetic hydrocolloids used as a viscosity enhancer/suspending agent
- sodium carboxymethylcellulose
example of synthetic hydrocolloid used as a viscosity enhancer/suspending agent
examples of clay used as viscosity enhancer/suspending agent
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