Composition of Suspension and Suspending Agents.

SUSPENSION:
A Pharmaceutical suspension is a disperse system in which internal phase is dispersed uniformly

as finely divided insoluble particles throughout the external phase.
 COMPOSITION OF SUSPENSION:
Substances commonly used in pharmaceutical suspensions include:
Salts of week acids such as carbonates, citrates, gluconates, phosphate, and tartrates. Amongst
these, citrates and phosphates with their respective pharmaceutically accepted salts are
commonly used in pharmaceutical suspensions.
Formulation Aspects
A perfect suspension is one, which provides content uniformity. The formulator must encounter
important problems regarding particle size distribution, specific surface area, inhibition of crystal
growth and changes in the polymorphic form. The formulator must ensure that these and other
properties should not change after long term storage and do not adversely affect the performance
of suspension.
Choice of pH, particle size, viscosity, flocculation, taste, color and odor are some of the most
important factors that must be controlled at the time of formulation.
Formulation Components:
The various components, which are used in suspension formulation, are as follows.
 API (Active drug substances)

 Wetting agents (They are added to disperse solids in continuous liquid phase.)
 Flocculating agents (They are added to floc the drug particles)
 Thickeners (They are added to increase the viscosity of suspension).
 Buffers and pH adjusting agents (They are added to stabilize the suspension to a desired
pH range.)
 Osmotic agents (They are added to adjust osmotic pressure comparable to biological
fluid.)
 Coloring agents (They are added to impart desired color to suspension and improve
elegance.)
 Preservatives (They are added to prevent microbial growth.)
 External liquid vehicle (They are added to construct structure of the final suspension.)
 SUSPENDING AGENTS:
Suspending agents also called thickening agents are used to stabilize suspensions are hydrophilic
colloid i.e. substances that spontaneously form colloidal dispersions with water because of an
affinity between the dispersed particles and the dispersion medium.
PROPERTIES:
 They help in lowering the sedimentation rate of particles in suspension.

 The sedimentation rate is slowed down by increasing the viscosity of liquid vehicle, and
slowing down settling in accordance to stokes law.
 They usually prevent caking at the base of an suspension .
 It could be resuspendend by agitation.
 It is majorly used as an excipients to help active pharmaceutical ingredients stay
suspended in formulation.
Examples : bentonite, carbomer, tragacanth, kaolin, carboxymethyl cellulose sodium etc.
TYPES OF SUSPENDING AGENTS:
1. POLYSACCHARIDES.
2. INORGANIC SALTS.
3. SYNTHETIC COMPOUNDS.
1. POLYSACCHARIDES.
The official suspending agents were natural polysaccharides but nowadays semi synthetic
compounds are increasingly used. Following are some examples of it: ACACIA,
TRAGACANTH, STARCH, ALGINATES, XANTHAMN GUMS.
ACACIA: This is dried exudates from Acacia senegal which occurs as round ovoid colorless or
white powder. It is often used as suspending agents. It is not a good suspending agent but it is
only used because of its protective colloidal property. It is useful for preparation of tinctures of
resinous materials that precipitate on addition of water. It is not very effective for dense. Acacia
mucilage becomes acidic on storage as a result of enzymatic activity and it contains oxidase
enzyme which may detoriate active ingredients Because of stickiness acacia is rarely used
externally.
TRAGACANTH: It occurs as thin, white or yellowish white, ribbon like flakes. It forms
viscous aqueous solutions. Its thixotropic and pseudo plastic properties make it better thickening
agent than acacia and can be used externally and internally. It is stable over pH 4 to 7.5.
2. INORGANIC SALTS: The following are examples of inorganic salts: Clay Bentonite
Aluminum magnesium silicate Aluminum hydroxide.
BENTONITE: Its formula is: Al2O3.4SiO2.H2O. It is subtype of montmorillonite clays, they
hydrate readily absorbing up to 12 times their weight of water particularly at elevated
temperatures. The gels formed are thixotropic in nature so act as good suspending agents. It is
used in concentration of 2 or 3% for external use such as calamine lotion
MAGNESIUM ALUMINUM SILICATE (VEEGUM): They are insoluble flakes that disperse
and swell readily in water absorbing the aqueous phase into crystal phase. They are used in
concentration of 5% both externally and internally. They are stable at pH 3.5 to 11.They are use
din combination with organic thickening agents such as xanthan gum , carboxymethyl cellulose.
They have high thixotropic and plasticity but presence of salts can alter these rheological
properties because of flocculating effect.
3. SYNTHETICS: These were introduced to over come various problems occurring from
natural products. Following are its examples Carbomers. Colloidal silicon dioxide.
CARBOMERS (CARBOXYPOLYMETHYLENE): This material is totally copolymer of

acrylic acid and allyl sucrose. It is used in concentration up to 0.5% for external preparations.
When dispersed in water it forms acidic, low viscous solutions, when adjusted to pH between 6
to 11 becomes highly viscous.
COLLOIDAL SILICON DIOXIDE(AEROSIL): When dispersed in water they form a three

dimensional network. It is used up to concentration of 4% for external use, also it is used as
thickening agent for non aqueous suspension. It is obtained from silicon dioxide and is white non
griffty powder. Because of fine particles it forms cake which cannot be easily redispersible.
___________________________________________________________________________

Composition of Suspension and Suspending Agents.

Uploaded by

Copyright:

Available Formats

Composition of Suspension and Suspending Agents.

Uploaded by

Document Information

Original Description:

Original Title

Copyright

Available Formats

Share this document

Share or Embed Document

Sharing Options

Did you find this document useful?

Is this content inappropriate?

Copyright:

Available Formats

Composition of Suspension and Suspending Agents.

Uploaded by

Copyright:

Available Formats

SUSPENSION:

A Pharmaceutical suspension is a disperse system in which internal phase is dispersed uniformly

Substances commonly used in pharmaceutical suspensions include:

 API (Active drug substances)

 They help in lowering the sedimentation rate of particles in suspension.

Examples : bentonite, carbomer, tragacanth, kaolin, carboxymethyl cellulose sodium etc.

TYPES OF SUSPENDING AGENTS:

CARBOMERS (CARBOXYPOLYMETHYLENE): This material is totally copolymer of

COLLOIDAL SILICON DIOXIDE(AEROSIL): When dispersed in water they form a three

You might also like