ABOUT SUSPENDING AGENTS AND ITS PROPERTIES.

1. SUSPENDING AGENTS
AND THEIR CLASSIFICATIONS

2. 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.
 They help in lowering the
sedimentation rate of particles
in suspension.

3.  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.

4. Types of suspending agents:
A. POLYSACCHARIDES.
B. INORGANIC SALTS.
C. SYNTHETIC COMPOUNDS.

5. A. POLYSACCHARIDES.
 The official suspending agents were
natural polysaccharides but nowadays
semi synthetic compounds are
increasingly used.
Following are some examples of it:
o ACACIA.
o TRAGACANTH.
o STARCH .
o ALGINATES.
o XANTHAMN GUMS.

6. 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

7.  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.

8. 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.

9. B . INORGANIC SALTS
The following are examples of inorganic
salts:
Clay
Bentonite
Aluminum magnesium silicate
Aluminum hydroxide

10. 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

11. 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.

12. C . SYNTHETICS
These were introduced to over come
various problems occurring from
natural products. Following are its
examples
Carbomers.
Colloidal silicon dioxide.

13. 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.

14. 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.

15. Thank you!
From SILVI SINGH
Roll No.13BPH094
Semester 5 , B.PHARM