oral- suspensions

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  • Created by: anna888
  • Created on: 01-03-23 13:46
describe suspensions
a liquid dipserse system containing particles distributed in a liquid vechile. coarse or collidal dispersions
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why are suspensions used
poorly water soluble drugs and to achieve controlled drug release
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describe the electrical double layer
water self ionises to produce ions. drug particles negative charged in liquid. eletrostatic repulsive forces between ions. stern layer, slipping plane, diffuse layer
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describe zeta potential. high vs low
in slipping plane. shows degree of repulsion and attraction between particles. high zeta potential- eletrostatic repulsive forces stronger, well dispersed. low zeta potential- v der waal attractive forces higher. floccules form
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describe excipients used in double layer
ionic salts eg nacl to increase mobile charge. surfactant used at belwo cm to increase suspension stability
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describe DVLO theory
considers balance between electrical repulsion and v der waals. predicts will particles settle or will they remain homoegnously dispersed
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features of a flocculated system
attractive v der waals higher than repulsive. particles exist as loosely bonded aggregates/floccules. easy redisperement. rapid sedimentation rate
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features of a deflocculated system
replusive forces higher than attractive. particles individual and dispersed. slow sedimentation rate but once sedimented very difficult to redisperse. not ideal
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what 3 things cause particle movement
brownains motion, gravity, external agitation
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describe diffusion, viscoity effect
brownains movement. particles <2 micrometers. high to low conc. less likely in flocculation as floccules are larger. higher viscosity less diffusion
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describe sedimentaton, what effects
caused by gravity. particles > 0.5 micromoles. smaller particle size and density rreduces. larger visocity or medium density reduces
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describe desirable sedimentation properties
slow is desired (deflocculated systems) but reversible is required (flocculated)
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expcients used in suspensions
palatability, preservatives (benzioc acid), buggers (citrate and phospahte), suspending agents (water soluble cellulouse polymers), flocculating agents (ionic salts and surfactants), chemical stabilers, wetting agents (imporve partcile distribution)
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Other cards in this set

Card 2

Front

why are suspensions used

Back

poorly water soluble drugs and to achieve controlled drug release

Card 3

Front

describe the electrical double layer

Back

Preview of the front of card 3

Card 4

Front

describe zeta potential. high vs low

Back

Preview of the front of card 4

Card 5

Front

describe excipients used in double layer

Back

Preview of the front of card 5
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