ABSTRACT
A coarse suspension is a system in which an internal, or suspended, phase is uniformly dispersed in an external phase, which is called the vehicle. The suspended phase is solid, and the vehicle may be either aqueous or non-aqueous. Dispersions of a solid in a liquid vehicle are also categorized according to the size of the suspended particles. Colloidal dispersions are suspensions in which the particle size is small enough that the suspended phase does not settle under the force of gravity; that is, the particles remain suspended by Brownian motion. The particle size in a colloidal dispersion ranges from about 1 nm to an upper limit of about 1 mm.
Examples of colloidal dispersions in the pharmaceutical world include association colloids such as micellar systems and lipsomes. Macromolecules such as proteins and DNA that have at least one dimension larger than about 1 nm also exhibit properties of colloidal systems.
