Basics
What is a disperse system?
A system where one phase is distributed throughout another phase.
What are coarse dispersions?
Dispersions with particle size 10–50 µm.
What is a suspension?
A preparation of finely divided particles in a vehicle with minimal solubility.
What is sedimentation?
The settling of particles under gravity.
What is rheology?
The study of flow and deformation of materials.
What is the dispersed phase?
The phase that is distributed throughout the medium.
What are fine dispersions?
Dispersions with particle size 0.5–10 µm
Why are suspensions needed?
Used when drugs are unstable in solution but stable in dispersed form.
What is Stokes’ Law?
The equation used to describe sedimentation rate.
What is viscosity?
Resistance to flow.
What is the dispersion medium (dispersing phase)?
The continuous phase that surrounds the particles.
What are colloidal dispersions?
Dispersions with particle size 1–500 nm
What is taste masking in suspensions?
A formulation designed to improve taste by reducing drug solubility.
Increasing this property slows sedimentation
viscosity
What are Newtonian fluids?
Materials with constant viscosity regardless of shear rate.
What are the five types of disperse systems?
Suspensions, emulsions, gels, magmas, and aerosols
What are dilute suspensions?
Suspensions containing 1–20% w/v solids
What are dry suspensions?
Suspensions that require reconstitution before use.
Larger particles cause this effect on sedimentation rate
increased sedimentation rate
What are non-Newtonian fluids? Name the 3 types
Materials whose viscosity changes with shear rate.
Plastic (Bingham bodies)
Pseudoplastic
Dilatant
What are the types of dispersed phases?
Solid, liquid, and gas.
What are concentrated suspensions?
Suspensions containing ~50% w/v solids.
What are desired properties of a pharmaceutical suspension?
A suspension that settles slowly but redistributes easily upon shaking.
What is caking?
A major stability issue where particles form a hard mass
What do the following equations tell us? n/n0 or (pt)/(poto)
Measurement of viscosity