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