Types of Suspending Agents

Types of Suspending Agents

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.

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