Products
Numerous drugs are commercially available as dispersions. These are liquid, semisolid and solid dosage forms.
Structure and properties
Dispersions are heterogeneous mixtures of substances that do not combine or dissolve. Dispersions consist of a disperse (internal) phase and an external (continuous, closed) phase. They are usually produced under agitation. A typical example is oil droplets in water. Because fatty oils are lipophilic and water is hydrophilic, the liquids do not dissolve into each other. The substances can be solid, liquid or gas and can be combined in any way.
Dispersions in pharmaceuticals
The following is a list of dispersions which are particularly important in pharmacy:
- Emulsions: Liquid in liquid
- Suspensions: Solid in liquid
- Foams: gas in liquid
- Powder mixtures: Solid in solid
- Aerosols: Liquid or solid in gas
Disadvantages of dispersions
Disadvantages of dispersions include that they become unstable, fall apart or flocculate over time. Suspensions must be shaken before each use.
