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UNDER THE ESTEEMED GUIDANCE OF
Mrs.PALLAVI. K M.Pharm
Vignan Pharmacy College 1
VIGNAN PHARMACY COLLEGE.
Approved by PCI,AICTE, New Delhi. Affiliated to JNTU,Kakinada.
Vadlamudi -522213, Guntur, A.P.
These are biphasic liquid dosage forms in which the particle
size of the dispersed phase ranges from 0.1mm.
These are mainly of 2 types
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Advantages & disadvantages
Packing of suspensions
Formulation of suspensions
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A Pharmaceutical suspension is a coarse
dispersion in which internal phase
(therapeutically active ingredient) is dispersed
uniformly throughout the external phase.
The internal phase consisting of insoluble solid particles
having a range of size(0.5 to 5 microns) which is
maintained uniformly through out the suspending vehicle
with aid of single or combination of suspending agent.
The external phase (suspending medium) is generally
aqueous in some instance, may be an organic or oily
liquid for non oral use.
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External phase :
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eg: Paracetamol suspension
antacids, Tetracycline HCl.
Externally applied suspension
eg :Calamine lotion.
eg: Procaine penicillin G
Insulin Zinc Suspension
Based On General Classes :
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Based on Proportion of Solid Particles:
Dilute suspension :Concentration ranges from 2 to
10% w/v solid.
Eg: cortisone acetate, predinisolone acetate
Concentrated suspension: Concentration ranges from
Eg: zinc oxide suspension
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Based on Size of Solid Particles :
•Suspensions having particle sizes of suspended solid less than
about 1micron in size are called as colloidal suspensions.
•Suspensions having particle sizes of greater than about 1micron in
diameter are called as coarse suspensions.
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Suspensions are the biphasic colloidal dispersions of
nanosized drug particles stabilized by surfactants.
Size of the drug particles is less than 1mm.
Nano suspensions (10 ng)
Suspension can improve chemical stability of certain
E.g. Procaine penicillin G.
Drug in suspension exhibits higher rate of bioavailability
than other dosage forms.
Order of bioavailability :
Solution > Suspension > Capsule > Compressed Tablet
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Physical stability , sedimentation and compaction can causes
It is bulky and sufficient care must be taken during handling
It is difficult to formulate.
Uniform and accurate dose can not be achieved unless
suspension are packed in unit dosage form.
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Sedimentation means settling of particle (or) floccules occur under
gravitational force in liquid dosage form.
Stokes equation :
d = Diameter of particle
r = radius of particle
vsed.= sedimentation velocity in cm / sec
ρ s= density of disperse phase
ρ o= density of disperse media
g = acceleration due to gravity
η o = viscosity of disperse medium in poise
(ρs -ρ0 )g
PROPERTIES OF SUSPENSIONS
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Limitation Of Stoke’s Equation :
Stoke's equation applies only to:
Spherical particles in a very dilute suspension (0.5 to 2 gm per
Particles which freely settle without collision .
Particles with no physical or chemical attraction.
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1.Sedimentation volume (F) or height (H) for flocculated
Sedimentation volume is a ratio of the ultimate volume of
sediment (Vu) to the original volume of sediment (VO)
F = Vu / VO
Vu = final or ultimate volume of sediment
VO = original volume of suspension before settling
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F has values ranging from less than one to greater than one.
The system is in flocculated equilibrium and show no clear
supernatant on standing.
Sediment volume is greater than the original volume due
to the network of flocs formed in the suspension.
When F=1 then Vu =Vo
When F >1 then Vu > V o
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Fig : Suspensions quantified by sedimentation volume (f)
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2.Degree of flocculation (β)
It is the ratio of the sedimentation volume of the flocculated
suspension ,F , to the sedimentation volume of the
deflocculated suspension, F∞
The minimum value of ß is 1,when flocculated suspension
sedimentation volume is equal to the sedimentation volume of
ß = F / Fo
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3.Brownian movement :
If particle size is about 2 to 5mm,
When the size of the dispersed particle approach that of
colloidal dimensions brownian movement sets in .
Equation for Brownian
In this system solids as present
as individual particles . they also
exhibit aggregation but
comparatively low than
Pleasant appearance because of
uniform dispersion of particles .
Particles exhibit repulsive forces
Particles settle independently
In this system solids aggregate
by forming chemical bridges .
Un slightly sediment and
supernatant layer is formed.
Particles exhibit attractive
They settle as flocs
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Rate of sedimentation is slow
and size of particle is small.
Particles exist as separate
Bioavailability is relatively
Rate is high as flocs are
collection of smaller particles.
Particles form loose
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The formulation of a suspension depends on whether the
suspension is flocculated or deflocculated.
Three approaches are commonly involved
1. Use of structured vehicle
2. Use of controlled flocculation
3. Combination of both of the methods
FORMULATION OF SUSPENSIONS
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Flow chart of formulation of suspension
Wetting agents They are added to disperse solids in continuous liquid phase.
They are added to floc the drug particles
Thickeners They are added to increase the viscosity of suspension.
and pH adjusting agents
They are added to stabilize the suspension to a desired pH
They are added to adjust osmotic pressure comparable to
They are added to impart desired color to suspension and
Preservatives They are added to prevent microbial growth.
They are added to construct structure of the final suspension.
INGREDIENTS FOR FORMULATION OF SUSPENSIONS
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Following consideration are important for manufacturing
Selection of right material that go into the manufacture.
The step involved and their sequence in the manufacture.
Preservation and storage of the product.
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• Grinding or levigating of insoluble material
• All soluble ingredients are dissolved in same portion of the
vehicle and added to the smooth paste to step1 to get slurry.
• The slurry is transformed to a graduated cylinder, the mortar
is rinsed with successive portion of the vehicle.
Steps involved in formulation of suspensions
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• Decide whether solids are:
• suspended in structured vehicle
• Flocculated and then suspended
• Make up the dispersion to the final volume
by adding suitable suspending agent
Pharmaceutical suspensions for oral use are generally packed
in wide mouth container having adequate space above the
liquid to ensure proper mixing.
Parenteral suspensions are packed in either glass ampoules or
Packaging of Suspensions
Theory of emulsification
Formulation of emulsions
Stability of emulsions
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An emulsion is a thermodynamically unstable system
consisting of at least two immiscible liquid phases one of which is
dispersed as globules in the other liquid phase stabilized by a third
substance called emulsifying agent.
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Simple emulsions (Macro emulsions)
These are clear transparent solutions
particle size ranges from 10-200nm.
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Water in oil type (W/O):
An emulsion is referred as water in oil, if the
dispersed phase is water and the continuous
phase is oil.
Ex: Butter ,salad dressings
Oil in water type (O/W) :
An emulsion is referred to as oil in water ,if
the dispersed phase is oil and the continuous
phase is aqueous base .
Ex : Turpentine liniment and Vanishing cream
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Oral products :
It covers the unpleasant taste
Increases absorption rate
Topical use :
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It depends on the use to which an emulsion is required.
Selection based on HLB for an emulsion which may be o/w or w/o
may be given as follows
To produce emulsions of o/w type emulsifiers in the HLB value
range of 8-18 are tried and for w/o type HLB 3-16 are tried.
Second method :
Griffin evolved a series of required material to be emulsified .
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The amount of emulsifier to be added for an emulsion can be
calculated with HLB values of emulsifiers using the following
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Substance HLB value for o/w
HLB value for w/o type
Cotton seed oil 6-7 -
Petrolatum 8 -
Beeswax 9-11 5
Paraffin wax 10 4
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Comparsion of HLB values of o/w and w/o types of
various substances :
Droplets can be stabilized by three methods :
i) By reducing interfacial tension
ii)By preventing the coalescence of droplets.
a. By formation of rigid interfacial film
b. By forming electrical double layer
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Emulsifying agents or Surface active agents or
hydrophilic colloids or finely divided solid
particles are needed to decrease the interfacial
Interfacial tension increases
Interfacial Area increases compared to original
Liquid broken into fine particles
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Solid particle films
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Mono molecular Multi molecular Solid particle
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Electrical double layer at oil-water interface
It is done by two methods :
Small scale method :
i) Wet gum method &
ii) Dry gum method
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Wet gum method
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Emulgent is placed in the mortar
Water is added to the emulgent and
is dispersed to form a mucilage
Oil is added in small amounts with
continuous titrations .
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Emulgent is placed in the mortar
Oil is added to the emulgent and
is dispersed to form a mucilage
Water is added at a time with
rapid continuous titrations .
Ii. Creaming or sedimentation
iii. Aggregation or coalescence
iv. Phase inversion
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Re dispersible association of particle within an emulsion to form
Precursor to the irreversible coalescence.
Differs from coalescence mainly in that interfacial film and
individual droplets remain intact.
Influenced by the charges on the surface of the emulsified globules.
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Creaming is either upward movement or downward movement
of dispersed droplets of emulsion relative to the continuous
phase ( due to the density difference between two phases).
Rate of creaming can be calculated using Stoke’s law
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Dispersed particles come together but do not fuse.
It is the process by which emulsified particles merge with each to
form large particles.
It is the destroying of the film surrounding the particles.
The major factor to prevent coalescence is increasing the
mechanical strength of the interfacial film.
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An emulsion is said to invert when it changes from an o/w to w/o or
It occurs due to :
Addition of electrolyte
Addition of CaCl2 into o/w emulsion by sodium soaps can be
inverted to w/o.
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Microbial contamination may occur due to:
Usage of impure raw materials
Poor sanitation conditions
Invasion by an opportunistic microorganisms.
Contamination by the consumer during use of the product..
Precautions to prevent microbial growth
Use of uncontaminated raw materials
Careful cleaning of equipment with live stream .
Addition of Preservative agent.
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These are biphasic liquid preparations
containing two immiscible liquids one of
which is dispersed as minute globules into
These are biphasic liquid dosage form of
medicament in which finely divided solid
particles are dispersed in a liquid
Globule size of the dispersed liquid is in the
range of 0.25 to 25µm
Particle size of suspended solid is in the
range of 0.5 to 5 microns
Emulsifying agent is required to make a
Suspending agent is required to make a
Emulsions are of two types oil-in-water type
and water-in-oil type
Suspensions are of two types flocculated
There are several tests to confirm type of
There are no tests to confirm type of
During storage freezing should be avoided
as it may lead to cracking
During storage freezing should be avoided
as it leads to aggregation
Differences between Emulsions and Suspensions
To date Emulsions and Suspension have been shown to
produce distinct advantages like
Controlled Drug release
Protection of Thermolabile drugs
Reduced patient Variability
Hence these formulations provide a broad scope in
the present and future research.
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Physical pharmaceutics by Manavalramaswamy Page
Martin A. Fourth edition, “Coarse dispersion”
Physical Pharmacy, Lippincott Williams and Wilkins,
Philadelphia 2001, Page No. 479-481.
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Text Book of Physical Pharamaceutics, Subramanyam C.V.S.,
Second edition, “Suspensions and emulsions’’ PageNo. 374-387.
Tutorial Pharmacy, Cooper & Gun, Sixth edition, “Dispersed
system” Page No. 75-78,
I sincerely thank my guide K. Pallavi madam for her support
I am very thankful to our respected Principal Dr. P. Srinivas
Babu sir and also to the seminar committee
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