Suspension, Coarse dispersion, B.Pharm IV sem

1. SUSPENSION
Kiran C Rodge
Shivlingeshwar college of Pharmacy,
Almala, Tq-Ausa,Dist-Latur,Maharashtra

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“A Pharmaceutical suspension is a biphasic liquid
dosage form in which internal phase is dispersed
uniformly as finely divided insoluble particles throughout
the external phase, The range of dispersed solid particles in
suspension from 0.5 to 5.0 micron. ”

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Ideal Properties of Suspension
Particle size should be small & uniform.
Re‐ suspension of particles occur easily.
Dispersed particles do not settle rapidly after shaking
Cake formation not occur during its shelf life.
Maintain its stability and elegance during its shelf life
Isotonic & non‐irritating
Particle size less than 5 μm.
Sterility during its storage & use.
Syringeability & injectability

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Advantages of Suspension
Suspension can improve chemical stability of certain
drug.
Drug in suspension exhibits higher rate of
bioavailability than other dosage forms. Solution >
Suspension > Capsule > Compressed Tablet > Coated
tablet
Duration and onset of action can be controlled
Suspension can mask the unpleasant/bitter
taste of drug.

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Disadvantages of Suspension
Physical stability, sedimentation and
compaction can causes problems.
It is bulky. Sufficient care must be taken
during handling and transport.
Uniform and accurate dose may not be achieved.

6. Types Of Suspension
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1.General Use
a. Oral
b. Topical
c. Parenteral
2. Proportion of solid Particles
a. Dilute Suspension
b. Concentrated Suspension

7. Types Of Suspension
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3.Size of solid particles
a. Corse Dispersion (More than 0.2 μm)
b. Colloidal Dispersion (In between 0.1-0.2 μm)
c. Molecular Dispersion ( Less than 1 nm)
4. Electrokinatic nature of solid
a. Flocculated Suspension
b. Deflocculated Suspension

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Particle-Particle
Interaction

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DLVO Theory
 The scientists Derjaguin, Landau, Vervey and Overbeek developed a theory in the
1940s which dealt with the stability of colloidal systems.
 DVLO theory suggests that, the stability of a colloidal system is determined by the
sum of the Vander Waals attractive (VA) and electrical double layer repulsive (VR)
forces that exist between particles as they approach each other due to the Brownian
motion they are undergoing.
 The Vander waal forces depend on chemical nature and size of particle.
 The electrostatic repulsive forces depend on density, surface charge and thickness of
double layer.

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DLVO Theory

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Conclusions may be drawn from the energy curves
Primary minimum (sign of precipitation) : When particles are very close to each
other, atomic orbitals overlaps and penetrate each other This is indicated by a rapid
rise in potential energy. The net result is a stronger attraction which leads to
precipitation.
Net Energy peak (sign of better stability) : At intermediate distances, appropriate
repulsive forces operate {positive zeta potential energy). This potential barrier 'keeps the
particles in Brownian movement and imparts stability to the dispersion.
At this peak, the maximum potential is designated. by Vn,
The stability of a colloidal system, is defined by the height of the maximum in the
potential energy curve.

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Conclusions may be drawn from the energy curves
Secondary minimum (sign of aggregation): This is observed when particles are
separated by long distances. about 1000 A0 to 2000 A0. Particles experience attraction
forces and form aggregates.

15. Interfacial Properties of solid
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An acceptable suspension should not exhibit settling of
dispersed solids. This can be achieved by reducing the
particle size to 5μm that they exhibit Brownian motion.
Since size reduction implies that work (W) has to be
done to divide large particles to smaller particles, this
process can be written as:

16. During size reduction, the surface area of the solids increases
enormously leading to an enhanced surface free energy (ΔG),
a state in which the system is thermodynamically unstable,
Now, the system spontaneously reacts and tends to return to
a stable state in order to reduce its surface free energy
(ΔG = O).
Two approaches are possible to regain stability.
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 In above equation ΔA may be reduced to
zero, so that ΔG will become zero.
 In above equation, the interfacial tension,
ϒSL may be reduced, so that the system
can be stabilized.

17. Factors Influencing settling
⪢ Theory of Brownian Movement
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18. Factors Influencing settling
⪢ Theory of Sedimentation
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19. PHYSICAL STABILITY
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Physical stability is defined “the condition, in which
the particles remain uniformly distributed through out
the dispersion without any signs of sedimentation.”
It is difficult to achieve this condition. Hence, the
definition can be redefined as – “if the particles settle,
they should be easily dispersible by a moderate amount
of shaking.”

20. 1.Sedimentation Volume
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The extent of sedimentation is quantitatively expressed
by two parameters

21. 2. Degree of Flocculation
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22. FORMULATION OF
SUSPENSIONS
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Thanks!
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