1. Natural polysaccharides
(a) Acacia: Protective colloid and suspending agent
used in a preparation containing resinous tincture that precipitates on the addition
of water.
(b) Tragacanth: Better than acacia, used to suspend
heavy diffusible substances.
(c) Alginates: 1-5% Viscous in nature immediately
after preparation but the viscosity decreases within 24 hours. Alginate mucilage must not be heated above
60°C due to polymerization its viscosity is lost.
2. Semi-synthetic derivative
(a) Methyl cellulose – 0.5 to 2% (sol to gel, gel to
sol)
(b) SCMC – 0.25%-1% (oral, external, IV)
(c) Microcrystalline cellulose – insoluble in water, but
shows a good dispersion.
• Used in combination with MC, and HPMC to flocculate
dispersion.
3. Inorganic agents
(a) Bentonite – 3% for external use.
(b) Magnesium aluminiun silicate (veegum) – 5%.
4. Synthetic compound
(a) Carbamers – 0.5% conc.
(b) Colloidal silicon dioxide – 4% for external use.
5. Wetting agents: These substances reduce the
surface tension between solid particles and liquid medium. This is achieved by
the solid-liquid interface in such a way that the affinity of the particles
towards the surrounding medium is increased, thereby helping in the penetration
of liquid into the particles, thus resulting in good suspension (0.5%), for
example: Spans and tweens etc.
6. Preservative substances which protect substances
from bacterial growth. They should be stable and compatible. e.g. Benzoic acid,
methyl and propylparaben, EDTA.
7. Organoleptic agent
(a) Flavouring agent – e.g. Vanilla, Strawberry,
Banana.
(b) Sweetening agent – Sucrose, Sodium saccharin,
Aspartame.
(c) Coloring agent – Sunset yellow, Tartrazine,
Erythrosine.
(d) Perfumes – Rose water and Lavender oil.
8. Chemical stabilizers: To maintain the stability of
the formulation. e.g. Citric acid, disodium diedetate, sodium citrate.