1. Suspension containing diffusible solids:
• The drug is finely powdered with other
ingredients.
• 3/4th of the vehicle is added to make cream.
• Addition of rest of vehicle.
• Volume is makeup.
• Suspension is labelled properly and corked e.g.
Light kaolin, light Magnesium carbonate, Sodium bicarbonate, Peppermint
water.
Labeling:
Shake well before use.
2. Suspension containing indiffusible
solids:
Prepared by using compound tragacanth and Tragacanth
mucilage (mixture of tragacanth, ethanol, and chloroform water) e.g., Aspirin, Chalk, Phenobarbitone, Zinc
oxide.
Note: Formulation
method of suspension using
1. Tragacanth mucilage
2. Compound tragacanth powder
The procedure is the same as that of diffusible solid
additional point is step one where the drug is also triturated with a suspending
agent with the addition of vehicle in small quantities and then the reset
procedure is the same.
3. Suspension containing precipitate
forming liquid:
Liquid preparation containing resinous matter when
mixed with water shows precipitation of resin, which sticks to the walls of the
container and tolu tincture. To prevent this compound tragacanth or Tragacanth
mucilage is used e.g. Myrrh, Tolu, Lobelia.
4. Suspensions containing poorly wettable
solids:
Some substances like sulfur and Hydrocortisone are both insoluble in water
and poorly wettable by it. In these types
of suspension, a suitable wetting agent is added which is adsorbed at the solid-liquid
interface in such a way that the affinity of particles for the surrounding
medium is increased and interparticular forces are decreased. E.g. Sulfur lotion – quilliar tincture is
used as a suspending agent.
5. Suspension produced by chemical
reaction:
e.g. MgSO4
+ (NaOH)2 + Na2SO4
For preparing milk of magnesia suspension (antacid).
Precipitate is produced by chemical reaction.