Learning Objective

•  Disperse systems and their types

Disperse systems consist of particulate matter known as the dispersed phase, distributed throughout a continuous or dispersion medium. Based on the size of the dispersed phase, these are classified into following three types:

1.  Molecular dispersion: less than 1 nm
2. Colloidal dispersion: From 1 nm to 0.5 μm
3. Coarse dispersion: Greater than 0.5 μm

Learning Objective

• Basic principle of suspensions

Suspensions are biphasic, heterogenous systems in which finely divided insoluble solid particles (disperse phase) are dispersed or suspended in a vehicle (dispersion medium). The diameter of the disperse phase may range from 0.5 μm to 100 μm. Systems in which the particle size diameter falls below this range are termed colloidal (1 nm–0.5 μm).

A suspension would be considered stable if after agitation (shaking), the drug particles are homogeneously dispersed for a sufficient time to ensure that an accurate dose is removed for administration to the patient.

Suspensions can be used as oral dosage forms, applied topically to the skin or given parenterally by injection.