Page 36 - Course Guide 2019

Suspending agent could be divided into different groups:

- Polysaccharides
o Natural
 Acacia mucilage (40% w/v)
 Compound tragacanth powder (2 – 4% w/v)
 Sodium alginate mucilage (25% v/v)
 Tragacanth mucilage (25% v/v)
 Tragacanth powder (0.2% w/v)
o Semi-synthetic
 Methylcellulose (0.5 – 2 % w/v)
 Hydroxyethylcellulose (0.5 – 2% w/v)
 Sodium carboxymethylcellulose (0.5 – 2% w/v)
 Microcrystalline cellulose (10 – 20% w/v

- Inorganic agents (external preparations)
o Clays
 Bentonite (2% w/v)
 Aluminium magnesium silicate (0.5 – 2% w/v)
o Aluminium hydroxide
 Colloidal hydrated aluminium hydroxide

- Synthetic
o Carbomer (0.1 – 0.4% w/v)
o Colloidal silicon dioxide (1.5 – 4% w/v)

9.3 EMULSIONS
Emulsions consist of a dispersed liquid phase in the form of small globules, in another liquid
phase. These two liquid phases are usually immiscible, but the formation of emulsions is made
possible with the help of emulsifying agent(s). The dispersed liquid phase is called the ‘internal
phase’, whilst the dispersion medium is called the ‘external/continuous phase’.
There are several important points that need to be remembered to produce a good emulsion
system:

- The internal phase should be between 20% – 60%. In the case whereby the internal
phase is less than 20%, another fixed oil should be added to increase the internal
phase volume.
- For internal administration, oil-in-water emulsion is more suitable and would be more
acceptable as compared to the water-in-oil emulsion.
- For external application, both oil-in-water and water-in-oil emulsion can be prepared
and used depending on the need.
- Suitable emulsifying agent(s) is necessary to ensure the formation of stable emulsion
systems.