Suspensions are biphasic liquid dosage forms consisting of undissolved particles in a vehicle, with ideal qualities including chemical stability and appropriate particle size for various uses (oral, topical, parenteral, and ophthalmic). Various classification methods exist based on particle size and pharmaceutical application, and there are essential additives to enhance stability and dispersion. While suspensions can mask unpleasant tastes and improve drug bioavailability, they pose challenges like physical stability and difficulty in formulation.

1. SUSPENSION
BY: LIPANJALI BADHEI

2. SUSPENSION
 The physical chemist defines the word “suspension”
as two-phase system consisting of an undissolved
or immiscible material dispersed in a vehicle (solid,
liquid, or gas).
 Suspension are generally taken orally or by
parenteral rout & the suspension are meant for
external use should have small particle size to avoid
gritty feeling to the skin
 The suspensions have dispersed particles above the
colloidal size that is 0.5-5 micron size.
“Pharmaceutical Suspension are biphasic liquid dosage form of
medicament in which the finely divided solid particle are
dispersed/suspended in the dispersion medium.”

3. Qualities of Ideal Suspension
An ideal suspension should have following properties:
1. It should be chemically stable.
2. The particle should not form compact cake on settling which otherwise difficult to redisperse.
3. The dispersed particles should not settle readily and the settled particles should redisperse
immediately on shaking.
4. The suspension should have such viscosity that it can be easily poured from the container.
5. Suspension for internal use must be palatable.
6. Injectable suspension should have a particle size that can pass through the needle.
7. Suspension meant for topical application should have small particle size to avoid gritty feel
and to avoid greater coverage of the area of application.

4. Classification
• Based On Pharmaceutical Use
– Oral suspension
– Externally applied suspension
– Parenteral suspension
– Ophthalmic Suspension
• Based On Proportion Of Solid
Particles
– Dilute suspension (2 to10 percnt;
w/v solid)
– Concentrated suspension (50
percnt; w/v solid)
• Based On Electrokinetic Nature Of
Solid Particles
– Flocculated suspension
– Deflocculated suspension
• Based On Size Of Solid Particles
– Colloidal suspension (< 1 micron)
– Coarse suspension (>1 micron)
– Nano suspension (10 ng)

5. TYPES
Flocculated Non-flocculated
The individual particles are in
contact with each other & form a
network like structure.
The individual Particles exist as
separate entities
Rate of sedimentation is high Rate of sedimentation is slow
Unstable Suspension Stable suspension
Sediment is loosely packed and
doesn’t form a hard cake
Sediment is very closely packed and
a hard cake is formed
Sediment is easy to redisperse Sediment is difficult to redisperse
Suspension is not pleasing in
appearance
Suspension is pleasing in
appearance
The floccules stick to the sides of the
bottle
They don’t stick to the sides of the
bottle
Clear supernatant Cloudy supernatant

6. According to Pharmaceutical use Suspension are 4 Type:
1. Oral Suspension
2. Topical Suspension
3. Parenteral Suspension
4. Ophthalmic Suspension

7. Oral suspensions
 Oral suspensions permit the formulation of poorly soluble drugs in the form of liquid dosage form.
 As these suspensions are to be taken by oral route therefore they must contain suitable flavoring and
sweetening agents.
 Drugs, which possess unpleasant taste in solution dosage form like paracetamol, chloramphenicol
palmitate etc. can be formulated as palatable suspension as they are suitable for administration to
pediatric patients.
Topical suspensions
 These suspensions are meant for external application and therefore should be free from gritty particles.
 There consistency may range from fluid to paste.
 Example of fluid suspension includes calamine lotion, which leave a deposit of calamine on the skin after
evaporation of the aqueous dispersion phase.

8. Parenteral suspensions
 These suspensions should be sterile and should possess property of syringability.
 Parenteral suspensions are also used to control the rate of absorption. As the absorption rate
of the drug is dependent on the dissolution rate of the solid. Therefore by varying the size of
the dispersed solid particles the duration and absorption can be controlled.
Ophthalmic suspensions
 These should also be sterile and should possess very fine particles.
 Drugs, which are unstable in aqueous solution, are formulated as stable suspensions using
non-aqueous solvents.
 For example fractioned coconut oil is used for dispersing tetracycline hydrochloride for
ophthalmic use.

9. Formulation Additives
They are added with the objective to increase apparent viscosity of the continuous, phase thus
preventing rapid sedimentation of the dispersed particles.
a) Natural Polysaccharides :Gum acacia, Tragacanth, sodium Alginate, Xanthan Gum
b) Semi-Synthetic Polysaccharides: Sodium Carboxymethyl cellulose, Methyl cellulose,
Hydroxypropyl methyl cellulose, microcrystalline cellulose
c) Inorganic Agents: Clays, Aluminum Magnesium Silicate, Bentonite, Hectorite
d) Synthetic Agents: Carbomer, Colloidal Silicon dioxide
1. Suspending and
Thickening agents
2. Wetting Agents
3. Dispersing agent
4. Flocculating Agent
5. Preservative
6. Organoleptic Additives
1. Suspending and Thickening agents:

10. 2. Wetting Agents: Wetting agents are additives which are usually added to decrease this hydrophobicity.
These agents generally get adsorbed at the solid-liquid interface and promote wetting of the solid
particles by the liquid of the dispersion medium.
a) Surfactants: polysorbates, sorbitan, esters, sodium lauryl sulfate, sodium dioctyl sulfosuccinate
b) Hydrophilic Polymers: acacia, bentonite, colloidal silicon dioxide and cellulose derivatives
c) Hydrophilic Liquids: alcohol, glycerol, propylene glycol
3. Dispersing agent: These additives are generally added as an aid to uniform distribution and dispersion
of solid particles of the dispersed phase. Wetting agents such as surfactants are often employed as
dispersing agents.
4. Flocculating Agent: These are substances added to cause controlled aggregation of the particles of the
dispersed phase in a suspension. Examples of such agents include surfactants, electrolytes and
hydrophilic polymers.
5. Preservative: These are use to prevent microorganism growth. Eg. Benzoic acid, sodium benzoate,
Methyl Paraben, propyl paraben etc.
6. Organoleptic Additives: Coloring Agent, Flavoring Agent, Sweetening Agent (use in oral suspension
for masking the unpleasant test).

11. Formulation of Suspensions
 Suspensions containing diffusible solids
 Suspensions containing in-diffusible solids
 Suspensions of precipitate forming liquids
 Suspensions produced by chemical reactions

12. Suspensions containing diffusible solids
 Suspensions containing diffusible solids contains insoluble drug particle which are light in weight &
readily mix with water & remain suspended throughout the liquid for sufficient period of time after
shaking.
Mixed thoroughly by shaking and labeling properly
Add more vehicle to make the volume up
Add any liquid ingredient if present
More vehicles are then added and any foreign particle is strained through a muslin cloth.
Powder all the solid ingredient in mortar, add enough vehicle to form a smooth cream
Example: Magnesium Trisilicate Mixture

13. Suspensions containing in-diffusible solids
 Suspensions containing in-diffusible solids consist of substances, which do not remain distributed in the
dispersion medium and don’t dissolved in water when shaken for long time to ensure uniformity of dose.
 They are prepared by adding a suitable thickening agent to the vehicle, which increases the viscosity of the
vehicle and delays the separation or sedimentation of in-diffusible particles.
Example: Calamine Lotion
Mixed thoroughly by shaking and labeling properly
Add more vehicle to make the volume up
Add any liquid ingredient if present
Measure ¾ vehicles & triturate to form a smooth, if any foreign particle is strained through a muslin cloth.
Powder all the solid ingredient in mortar, mixed them all together and add compound tragacanth powder (thickening agent)

14. Suspensions of precipitate forming liquids
 Suspension Containing Precipitate Forming Liquids In case of liquid preparations containing resin, resinous
substances gets precipitated and may adhere to the side of bottle which will not diffuse upon shaking.
 To prevent this tendency, a suspending agents like compound tragacanth powder or tragacanth mucilage
are incorporated.
It is used as vehicle in water or chloroform water.
i. Mix the mucilage with equal volume of vehicle.
ii. Measure precipitate forming liquid in a dry measure
iii. Add slowly into the centre of the mucilage with rapid stirring.
iv. Dissolve the solid substances if any
v. Take about ¼ of vehicle and mix them well.
vi. Filter if any foreign particle present.
vii. Add any other liquid is present.
viii.Make the volume up and labelling perfectly.
Method using Tragacanth Mucilage.

15. i. Finely powder the in-diffusible solid, and diffusible solid in mortar and mix intimately with compound
tragacanth powder (CPT).
ii. Triturate the mixture with the vehicle to form a smooth cream and dilute gradually to about 50 percent of
final volume.
iii. Measure precipitate forming liquid in a clean and dry measuring cylinder and add it to the centre of
suspension.
iv. If suspension contain an electrolyte:
a. It should be well diluted to about half of there remaining vehicle.
b. It should be added slowly with constant stirring.
v. Observe the contents for foreign particles. If present remove with the help of glass rod or, filter it.
vi. Add any liquid ingredient present.
vii.Add the vehicle to produce final volume and transfer the suspension into bottle with a direction on label
"Shake well before use".
Method using Compound tragacanth
powder

16. Packaging and Storage of Suspensions
1. Should be packaged in wide mouth containers having adequate air space
above the liquid.
2. Should be stored in tight containers protected from: freezing, excessive
heat & light
3. Label: "Shake Well Before Use" to ensure uniform distribution of solid
particles and thereby uniform and proper dosage.
4. Stored in room temperature if it is dry powder (25 0C).
5. It should be stored in the refrigerator after opening or reconstitute (freezing
should be avoided to prevent aggregation)

17. Advantages
 Suspension can improve chemical stability of certain drug. E.g.Procaine
penicillin G
 Drug in suspension exhibits higher rate of bioavailability than other dosage
forms. bioavailability is in following order,
Solution > Suspension > Capsule > Compressed Tablet > Coated tablet
 Duration and onset of action can be controlled. E.g. Protamine Zinc-Insulin
suspension
 Suspension can mask the unpleasant/ bitter taste of drug. E.g.
Chloramphenicol

18. Disadvantages
 Physical stability, sedimentation and compaction can causes problems.
 It is bulky sufficient care must be taken during handling and transport.
 It is difficult to formulate
 Uniform and accurate dose can not be achieved unless suspension are packed in unit dosage form