This document discusses pharmaceutical suspensions. It defines suspensions as biphasic liquid dosage forms containing finely divided solid particles dispersed in a liquid or semisolid vehicle. Suspensions can be administered orally, parenterally, for ophthalmic or external use. The document outlines the key properties suspensions must have and different types of additives that can be included. It also describes common methods for preparing different types of suspensions and tests used to evaluate suspension stability.

1. Mr.P.C.Patil

2.  Suspensions are the biphasic liquid dosage form of
medicament in which the finely divided solid particles
ranging from 0.5 to 5μ are dispersed in a liquid or semisolid
vehicle.
 The solid particles act as dispersed phase whereas liquid/
semisolid vehicle acts as the continuous phase .
 Taken orally or by parenteral route or
 External application.

3.  Should settle slowly and should readily re-dispersed on
gentle shaking
 Should be chemically inert
 Suspended particles should not form a cake
 Should free from large particles
 Should pour readily and evenly from the container

4.  Oral suspensions
 Parenteral suspensions
 Ophthalmic suspensions
 Suspension for external use

5.  These are consumed by the patient by orally.
 Contains flavouring agents and sweetening agents
 E.g: chloramphenicol palmitate
 Advantages :
 easy to swallow the medicament
 Kaolin and chalk can administered in suspension in order to
act as absorbent of toxin or to reduces excess acidity in the
GIT.
 Disadvantages :
 Accuracy of dosage is less reliable as compared to solution
 All Suspension should be shaken before taking dose
 Long storage may leads to change in disperse system

6.  These are administrated by parenteral route . These
suspensions are required to fulfill the following qualities-
 There should not be any crystal growth in the suspension
during the storage
 Suspensions should be sterilized
 The concentration of solid particles should be between o.5to
30%
 Particle size of drug should be such that it can be easily
pass through needle of the syringe
 The viscosity of the suspension should not interfere with its
flow through the syringe

7.  These are not commonly used as compare to eye drops
 These are prepared only in those cases, when the drug is
insoluble in the desired solvent or unstable in the liquid
form.
 These suspensions must fulfill the following conditions:
 Should be sterilized
 Should be isotonic
 Should have desired viscosity
 Particle size of eye suspension should be fine enough so
that it should be non irritating to the eye
 Should be packed in suitable container so that it can be
easily instilled in the eye.

8.  Meant for external use
 E.g: lotions, inhalations, eardrops etc
 Lotions containing suspended particle evaporate when
applied to the skin leaving a thin layer of medicament
on the surface
 Lotions are easier to apply and less messy than many
other semisolid external preparations
 Lotions are meant for application on broken or
inflamed skin should be free from harmful micro
organisms.
 These contains very small particle to avoid grittiness.

9.  Rate of sediment is high
 Sediment is rapidly formed
 Supernatent liquid is clear
 Suspension is not in pleasing in appearance
 Particles form loose aggregates, and form a network like
structure.
 Sediment is easy to redisperse.
 Sediment is loosely packed and does not form a hard cake.
 The floccules stick to the sides of the bottle.

10.  Rate of sediment is slow.
 Sediment is slowly formed.
 Supernatent liquid is not clear.
 Suspension is pleasing in appearance.
 Individual particles exists as separate entry.
 Sediment is difficult to redisperse.
 Sediment is closely packed and a hard cake is formed.
 The floccules do not stick to the sides of the bottle.

11. Following additives are used
I. FLOCCULATING AGENTS:
 In order to improve the dispersability of insoluble drug particles by reducing
the surface tension and minimizing the flocculation
 Examples: sodium lauryl sulphate, tweens, spans and carbowaxes
II.THICKENING AGENTS: (hydrophilic colloids)
 It forms colloidal dispersions with water and increases the viscosity of
continuous phase .so that the solid drug particles remain suspended in the
continuous phase for sufficient long time to measure a uniform accurate dose
 Examples:
1.Polysaccharides:
a. natural : gum acacia, tragacanth, starch, sodium alginate
b. Semi synthetic: MC, Sod.Carboxy MC, MCC
2.Inorganic agents :clay , aluminium hydroxide
3.Synthetic compounds : carbomer, colloidal silicon di oxide

12. III.WETTING AGENTS:
 It reduces the interfacial tension between the solid drug particles and liquid
medium by absorbing at the solid/liquid interface in such a way that affinity of
the drug particles for the surrounding fluid is increased and the inter particular
forces are decreased, thus producing the suspension of required quality
 Examples: alcohol in tragacanth mucilage, glycerin in sodium alginate,
bentonite dispersion and polysorbate
IV.PRESERVATIVES :
 To preserve the suspension against bacterial growth
 Examples :benzoic acid ,sodium benzoate , methyl paraben , propyl paraben
V.ORGANOLEPTIC ADDITIVES:
 To enhance the patients acceptability or mask the unpleasant taste or
appearance of the preparation
 Coloring agents- saffron, cochineal red, caramel, coal tar dyes,
 sweetening agents- sucrose, dextrose, liquid glucose , sorbitol , simple syrup
 flavoring agents- orange or gentian infusion , benzaldehyde , vanillin ,
peppermint, menthol , anise/dill/cinnamon waters

13. 1.Suspensions containing diffusible solids
2.Suspensions containing in diffusible solids
3.Suspensions containing precipitate forming liquids
4.Suspensions produced by chemical reactions

14.  Contains insoluble drug particles which are light in weight and readily mix
with water and remain suspended throughout the liquid for sufficient period of
time after shaking such substance known as diffusible solids.
 Example: calcium carbonate, magnesium trisilicate, rhubarb powder ,light
kaolin
 General method of dispensing:
 Powder all the solid ingredients and add enough vehicle to form a smooth
cream
 Add more of vehicle to make it pourable
 Remove if any foreign particle present by passing through muslin cloth
 Rinse the mortar and pestle with successive volume of vehicle until they are
quite clean
 Add if any liquid ingredients
 Add more of vehicle to adjust the final volume and mix thoroughly by shaking
the bottle
 Example: Kaolin mixture

15.  Contain substances which do not dissolve in water and do not remain evenly
distributed in the vehicle for sufficient period of time to ensure uniformity of
dose
 Example: calamine, zinc oxide ,hydro cortisone, aspirin , phenobarbitone
 General method of dispensing
 Powder and mix all the solid ingredients and add compound tragacanth powder
 Measure ¾th of the vehicle and triturate to form a smooth cream
 Remove if any foreign particle present by passing through muslin cloth
 Rinse the mortar and pestle with successive volume of vehicle until they are
quite clean
 Add if any liquid ingredients
 Add more of vehicle to adjust the final volume
 Example: Bismuth Carbonate Mixture

16.  Contains liquid substances that is precipitated on addition of water. These liquid
substances are insoluble and Indiffusible and it is difficult to redisperse on shaking.
 Example: compound benzoin tincture, myrrh tincture
 General method of dispensing(using tragacanth powder)
 Powder and mix all the Indiffusible and diffusible solid ingredients
 add compound tragacanth powder and mix
 measure half of the vehicle and incorporate small amount of it to the powders to form a
smooth cream and add remaining part of the vehicle
 Add precipitate forming liquid in a slow stream in the centre of the cream with rapid
stirring
 Dissolve the soluble ingredient if present in the vehicle and add slowly with constant
stirring
 Remove if any foreign particle present by passing through muslin cloth
 Rinse the mortar and pestle with successive volume of vehicle until they are quite clean
 Add if any liquid ingredients
 Add more of vehicle to adjust the final volume

17.  General method of dispensing(using tragacanth mucilage)
 Tragacanth mucilage is used when the vehicle is water or
chloroform water
 Mix the tragacanth mucilage with an equal volume of the vehicle
 Add precipitate forming liquid in a slow stream in the centre of the
mucilage with constant stirring
 Dissolve the solid substance if any, in about ¼th of the vehicle and
mix it with the above mixture
 Remove if any foreign particle present by passing through
muslin cloth
 Rinse the mortar and pestle with successive volume of vehicle
until they are quite clean
 Add if any liquid ingredients
 Add more of vehicle to adjust the final volume

18.  Some of the suspensions are prepared by the chemical
reactions between the ingredients used in the
formulations.
 In this reactants are highly diluted and mixed together
to form very finely divided precipitates that can be
easily distributed throughout the liquid by shaking.
 The precipitate so formed are diffusible in nature.
 Hence there is no need of adding any suspending agent
 Example: Sulphurated potash and zinc sulphate mixture

19.  The most stable pharmaceutical suspensions are
flocculated i.e. the suspended particles are bonded
together physically to form a loose, semi rigid structure
.
 The non flocculated suspensions can be made stable by
decreasing the particle size of the suspended material or
by increasing the density and viscosity of the vehicle

20. 1.Sedimentation method
 It is the most important parameter in the evaluation of the stability
 It is determined by keeping a measured volume of the suspension in a graduated
cylinder in an undisturbed position for a definite period of time and noted the
ultimate height of the sediment(Hu) and initial height of the total suspension.
 The sedimentation volume F is the ratio of the ultimate height and initial height
 The sedimentation volume can be plotted against time
 The graph indicates the sedimentation pattern of suspension on storage
 A stable suspension shows a horizontal or less steep curve.
 The evaluation of redisperbility can also be determined by shaking the suspension
and again find out the sedimentation volume

21. 2.Rheological Method
 The viscosity of the suspension is studied at different time
intervals by using a good quality of viscometer
 It gives useful information about the stability of suspensions
3.Electrokinetic Method
 The determination of surface electric charge or zeta potential
of suspension is helpful to find out the stability of suspension
 Certain zeta potentials produce more stable suspensions
because of controlled flocculation
 Zeta potential can be calculated from migration velocities of
the particles measured by electrophoretic method

22. 4.Micromeritic Method
 Stability of the suspension can be depends upon the particle
size of the dispersed phase
 The size of the particle in suspension may grow and may leads
to formation of lumps or craking
 Any change in particle size with reference to time will provide
useful information regarding the stability of a suspension
 A change in particle size distribution and crystal habit may be
studied by microscopy and coulter counter method

23.  STORAGE CONDITIONS
 Should be stored in cool place but should not be kept in a fridge it
leads to aggregation of the suspended particals
 LABELLING
 Must be labeled as a
“shake well before use”
 CONTAINERS
 Should be packed in containers which are having adequate air space
above the liquid to permit adequate shaking
 Oral suspensions should be packed in wide mouth bottles to permit
prompt removal of the suspension