This ppt deals with a brief overview on suspension that is helpful for both D.Pharm & B.pharm students.

1. A BRIEF NOTE ON
SUSPENSION
By:-
Diptee Gupta
Assistant Professor
Seth Vishambhar Nath
Institue of Pharmacy,
Lucknow
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2. • Suspension are biphasic liquid dosage form of
medicament in which finely divided solid
particles ranging from 0.5 to 5 micron are
suspended or dispersed in a liquid or semi solid
vehicle.
• The solid particles constitute the discontinuous
phase whereas liquid vehicle constitute the
continuous phase.
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3. Ideal properties of suspension
• The sediment or creaming produced on storage if any,
must be easily re-suspended by moderate agitation of the
container.
• The product must remain sufficiently homogenous for at
least the period between shaking the container & removing
the desired amount.
• The product may be required to thickened in order to
reduce the rate of settling of particles.
• Any suspended particles should be small & uniformly size
in order to give a smooth elegant product free from gritty
texture.
• The suspension must be aesthetically pleasant.
• The flow properties of suspension should enable the
formulation to be easily poured from the container.
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4. Advantage of suspension
• Used to mask the taste of therapeutic agent.
• Used to administer the drug to patients who
have difficulty in swallowing solid dosage form.
• May be formulated to provide controlled drug
delivery. Eg: IM injection
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5. Dis-Advantage of suspension
• Fundamentally unstable preparation & require
formulation skill to ensure the physical stability
over the period of shelf life.
• Suspension may be bulky & therefore difficult
for a patient to carry.
• The formulation of aesthetic suspension is
difficult.
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6. Difference between flocculated &
deflocculated suspension
Flocculated suspension Deflocculated suspension
Particles form loose aggregate &
form a network like structure
Particle exist as separate entities
Rate of sedimentation is very high Rate of sedimentation is very low
Sediment is rapidly formed Sediment is slowly formed
Sediment is loosely packed & does
not form a hard cake
Sediment is closely packed & a hard
cake is formed.
It is easy to redisperse Difficult to redisperse
Not pleasing in appearance Pleasing in appearance
Floccules stick to the side of bottle Floccules do not stick to the side of bottle
Less bioavailability High bioavailability
High shelf life low shelf life
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7. Method of preparation of suspension
1. Suspension containing diffusible solids: Diffusible solids
do not dissolve in water but on shaking the powder can diffuse
evenly throughout the liquid for sufficient long time & allow
uniform distribution of drug in each dose.
Eg – calcium carbonate, light kaolin, light magnesium carbonate
Method of dispensing:
Diffusible solids converted into powder in a mortar & mix with
soluble drug.
Add 3/4th part of vehicle to form a smooth paste.
Add volatile liquid if any, mix well & Make up the final volume by
adding vehicle & transfer it to bottle.
Label it “SHAKE THE BOTTLE WELL BEFORE USE” & dispense.
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8. 2. Suspension containing indiffusible solids:
Indiffusible solids do not remain evenly distributed in
a vehicle on shaking for sufficiently long time.
Suspending agents used to correct this type of problem.
The two commonly used suspending agents are:
1) Compound tragacanth powder: which is used in
ratio of 2g/100ml of suspension
2) Tragacanth mucilage used in ration in 1/4th
volume of suspension to be preparaed.
Indiffusible solids eg: aspirin, Phenobarbitone,
calamine, hydrocartisone, zinc oxide.
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9. Evaluation of suspension
• A number of procedures has been suggested for
evaluating the physical stability of suspension.
• Physical stability means “the condition in which
particles remain uniformly distributed throughout
the dispersion without any signs of sedimentation.”
• Following methods used for evaluation of
suspension:
1. Sedimentation method
2. Rheological method
3. Electro kinetic method
4. Micrometric method
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10. 1. Sedimentation method:
The formation of sediment & its redispersibility are the 2
features related to elegance of suspension. The extent of
sedimentation can be expressed by 2 parameters ( applicable
only for flocculated suspension):-
a) Sedimentation volume (F): it is the ratio of the ultimate
height (Hu) of the sediment to the initial height (Ho) of total
suspension.
• It is dependent on time.
• If F=1, there is no sedimentation , suspension looks elegant &
practically acceptable
• If F<1, rapid settling of dispersed phase
• If F>1, network of flocculation loose
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11. b) Degree of flocculation:
• If β = 1, the extent of flocculation.
• The higher the value of β, the greater will be
physical stability.
• It is the destructive method as flocculated
system is converted to deflocculated system by
adding the deflocculating agents.
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12. Redispersibility: it is an important criteria of
physical stability.
• 100 ml suspension is placed in a graduated
cylinder- allowed to settle.
• After that cylinder is rotated at 20rpm through
360 & when base of cylinder is clear of sediment
then the end point is noted.
• Lower the number of revolution or shorter time
for redispersion- faster dispersibility.
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13. 2. Rheological Method:
• These method used to help in predicting the
settling pattern. Brookfield viscometer with T
spindle is used to study the viscosity of
suspension
• Consistency of suspension is evaluated by –
cup& bob Viscometer and cone & plate
viscometer.
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14. 3. Electro kinetic method:
Determination of surface electric charge or zeta
potential of suspension is helpful to find out the
stability of suspension.
Certain zeta potential produce more stable
suspension due to controlled flocculation.
Zeta potential can be calculated from migration
velocity of particles measured by electrophoretic
method.
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15. 4. Micrometric method:
• The stability of suspension depend on the
particle size of dispersed phase. The size of
suspended particles may grow & lead to
formation of lumps or cake.
• So change in particle size with time provide
useful information about stability of suspension.
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