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Suspensions definition
Contain finely divided solid (suspensoid) distributed giving minimum degree of solubility.
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The dispersed phase is _____ where as the contiunous phase is _____.
Internal, external
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Examples of dispersed phase are
- Colloidal
- Suspensions
- Emulsions
- Microemulsions
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T/F There is no such thing as an IV suspension
True
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Advantages of oral suspensions
Easy to swallow and flexible dosing
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Disadvantages of Oral suspensions
- Microbial growth
- relative instability (vs solids)
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Comminutions is what?
Particle size reduction
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Process of making oral suspension
Solid drug is comminuted, wetted, then suspended.
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Three important issues for suspensions
- Particle Size
- Particle wetting
- Physical stability
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Goal for particle size
1-50 micrometers in diameter
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3 industrial ways to reduce particle size
- Micropulverization- 1-050 Micro meters
- Jet milling- <10 micro meters
- Spray drying
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Other methods of particle reduction
- Electric grinder
- Spatulations
- Titrutition
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Problems with particle wetting
Some problems are that the drug might be hydrophobic or there are air pockets
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Suspension can be irreversibly altered by these 3 types of physical instability
Particle settling, aggregation, and growth.
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Stokes equation, what do the variables stand for?
- V- falling velocity
- d- diameter
- Ro1- density of sphere
- ro2- density of liquid
- g- gravity
- n- viscosity of dispersion
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Stokes parameters
- Particle size
- Particle density
- Dispersion medium viscosity
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As particle size decreases what increases?
Interfacial surface area and free energy
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These are types of interparticulate forces
- Electrostatic- (keeps particles apart)
- Van der waal- (keeps them together)
- Repulsive hydration
- Adhesive
- Steric Repulsive
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Particles aggregate very strongly at _____ and weakly at ________.
- Primary minimum (close distance)
- Secondary minimum (far distance)
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Coagulation means
to drive together (strongly bound at primary minimum)
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Caking definition
Combination of settling and coagulation makes a non-redispersable sediment.
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Flocculated is usually at the _______ minimum
Secondary, loose and wooly. Easier to redisperse
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Ostwald ripening is the growth of large particles at the expense of ______.
Small particles
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Ostwald ripening is accelerated by
Temperature fluctuation
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Wetting agents help _____ the solids, Flocculating agents help keep them ____, and suspensing agents help keep the solids ______.
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Types of wetting agents are
Surfactants, solvents, and certain polymers
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examples of surfactants
- Anionic- docusate sodium
- Ionic- polysorbates (tweens)
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Solvent examples are
Alcohol, glycerol, propylene glycol
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Types of flocculating agents
Electrolytes, Surfactants, and Certain polymers
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T/F Dissolution depends on viscosity and bioavailabilty depends on dissolution
True
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For a newtonian liquid shear rate is _______. Viscosity is _______.
Linear function of shear stress
constant
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According to the graphs, as the line becomes more steeper it becomes _____ viscous.
Less
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For plastic liquids, minimum shear stress must be achieved for what to happen?
Flow
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A thixotropic liquid will __ when aggitated but will form a ___ when standing still.
Liquefy, Gel
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Hysteresis is when the restrictive network ______ reforms.
Slowly
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Xanthan gum is (ionic/anionic) and has ____ temperature stability, and a high _____.
- Anionic
- Good
- High viscosity
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Hydroxypropylmethylcellulose is a ______ polymer
nonionic
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Sodium carboxymethylcellulose is an _____ polymer
Anionic
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T/F Gums are not polysaccharides.
False, they ARE
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