The document summarizes a seminar on viscosity promoters. It discusses the ideal characteristics of viscosity promoters and provides a classification of various natural, synthetic, and inorganic viscosity promoters. Natural polymers discussed include natural gums like alginates, gum arabic, and carrageenan as well as cellulose derivatives like CMC, HPMC, and MC. Synthetic polymers like carbomer and PVP are also covered. The document concludes by discussing recent advances in using viscosity promoters for sustained ophthalmic drug delivery and modified chitosan for delivering bioactive molecules.

1. A SEMINAR ON
VISCOSITY PROMOTERS
Presented by
Sushma.A
M.Pharmacy (I
sem)
Industrial

2. CONTENTS
1.Introduction
2.Ideal characteristics of viscosity promoters
3.Classification
 Natural gums
 Cellulose derivatives
 Microcrystalline cellulose
 Chitosan
 Synthetic polymers
 Clays
4. Conclusion
References

3. INTRODUCTION
VISCOSITY:
Flow property of a simple liquid is expressed
in terms of viscosity. Quantitatively, viscosity is an
index of resistance of a liquid to flow.
 A fluid with large viscosity resists motion because its
molecular makeup gives it a lot of internal friction.
 A fluid with low viscosity flows easily because its
molecular makeup results in very little friction when it
is in motion.

4. VISCOSITY PROMOTERS:
These are substances ,which added to an
aqueous mixture, increase its viscosity without
substantially modifying its other properties , such as taste.
They provide body, increase stability , and improve
suspension of added ingredients.
It is desirable to increase the viscosity of liquid to
provide or to improve palatability or pourability

5.  Polymers are used in suspensions, emulsions , and
other dispersions ,primarily to minimize or control
sedimentation
 Only small amounts of many polymers(depending on
chemistry and molecular weight)are needed to bring the
viscosity of an aqueous preparation to almost any
desired value
 Most of the polymer solutions or dispersions are
Non-newtonian.

6.  Many polymers of natural origin are attacked directly by
microorganisms. Even if the polymer chosen is totally
resistant to bacteria and molds , the aqueous medium
may allow growth , and a preservative is still necessary.
 certain inorganic agents are also used as viscosity
builders.
Examples : veegum (colloidal magnesium aluminium
silicate ) and microcrystalline silica

7. Advantages and Disadvantages due to viscosity of medium
Advantages:
 High viscosity inhibits the crystal growth.
 High viscosity enhances the physical stability
 High viscosity prevents the transformation of
metastable crystal to stable crystal

8. Disadvantages :
 High viscosity hinders the re-dispersibility of the
sediments.
 High viscosity retards the absorption of the drug.
 High viscosity creates problems in handling of the
material during manufacturing.

9. IDEAL CHARACTERISTICS OF VISCOSITY
PROMOTERS:
Should produce a structured vehicle
Should have high viscosity at negligible shear during
storage and low viscosity at high shearing rates during
pouring
 Should exhibit yield stress
 Should be compatible with other excipients
Should be nontoxic
Viscosity should not be altered by temperature or on
aging

10. CLASSIFICATION:
 Natural gums
Acacia , Tragacanth
Alginic acid
Karaya , Guar gum etc.,
 Cellulose derivatives
Carboxy methyl cellulose
Methyl cellulose
Ethyl cellulose
Hydroxy ethyl cellulose
Hydroxy propyl methyl cellulose

11.  Microcrystalline cellulose
 Chitosan
 Synthetic polymers
carbomer (polyacrylic acid)
polyvinyl pyrrolidone
polyvinyl alcohol
 Clays
Magnesium aluminium silicate(veegum)
Bentonite , Attapulgite

12. 1) NATURAL GUMS
Natural gums are polysaccharides of natural origin ,
capable of causing a large viscosity increase in solution ,even
at small concentrations
These polymers may be either nonionic or anionic.
Natural gums can be classified according to their origin
1. Natural gums obtained from seaweeds
agar
alginic acid
sodium alginate
carrageenan

13. 2.Natural gums obtained from non-marine botanical
sources
 Gum arabic (from the sap of acacia trees)
 Gum tragacanth(from the sap of astragalus shrubs)
 Karaya gum(from the sap of sterculia trees)
 Guar gum(from guar beans)
 Locust bean gum(from the seeds of carob tress)
 Dammar gum (from the sap of dipterocarpaceae trees)

14. 3.Natural gums produced by bacterial fermentation
gellan gum
xanthan gum
ALGINATES
 Anionic polysaccharide
 Derived from brown seaweed in the form of monovalent
and divalent salts
 The most widely used one is sodium alginate
 Use :thickener and stabilizer

15. GUM ARABIC
 Anionic polysaccharide
 It is the dried exudate of trees of the genus acacia
 Unlike most natural gums,acacia exhibits very low
solution viscosities
 At concentration under 40% ,solutions exhibits newtonian
flow;higher concentrations behave in a pseudoplastic
manner
 Use: suspending agent,emulsifier,adhesives and binders
in tabletting

16. CARRAGEENAN
 Anionic polysaccharide derived from seaweed
 Solutions of carrageenan have a yield point when used
in sufficient concentration , and they are also thixotropic
 Use: emulsifier , thickener , suspension stabilizer
GUAR GUM
 Nonionic polysacccharide derived from seeds
 It exhibits pseudoplastic flow

17.  Disadvantage of these gels is the presence of insoluble
plant residue
 Use: thickener , suspension stabilizer
KARAYA GUM
 Anionic exudate polysaccharide
 The viscosity of gum karaya in water increases rapidly
with concentrations so that a dispersion with a
concentration of 2-3% acts as a gel
 Use : bulk laxatives , denture adhesives

18. LOCUST BEAN GUM
 Nonionic seed polysaccharide
 Solutions of this gum are psuedoplastic
 It is one of the more efficient thickening natural
polymers , along with guar , tragacanth , and karaya
gums
TRAGACANTH GUM
 Anionic polysaccharide
 It exhibit pseudoplastic flow
 It is one of the most efficient natural polymer thickeners

19. XANTHAN GUM
 Anionic polysaccharide
 Exhibits pseudoplastic rheology
 Temperature has very little effect on the viscosity of
xanthan gum solutions . This temperature independence
of viscosity is unique to xanthan gum
 Use : thickener , suspension stabilizer , suspending agent

20. Properties of Selected Viscosity-Imparting Agents
Agent Structure Ionic pH factors Rheology
charge
Alginates Poly anionic Stable at Pseudo
saccharide pH 3-10 plastic
Gum Poly Viscosity Newtonia
arabic saccharide anionic is affected n(<40%),
by pH peudoplas
tic(>40%)
Carragee- Poly anionic Stable at Thixotro-
nan saccharide pH 3-10 pic

21. Agent Structure Ionic pH Rheology
charge factors
Gum Poly anionic Stable at Pseudo
tragacanth saccharide pH 1.9-8.5 plastic
Xanthan Poly anionic Good Pseudo
gum saccharide stability at plastic
pH 1-12
Locust Poly Pseudo
bean gum saccharide nonionic --- plastic
Guar gum Poly anionic Stable at Pseudo
saccharide pH 4-10 plastic

22. Applications of natural gums:
 Guar gum is a colon- specific drug delivery carrier is
based on its degradation by colonic bacteria
 Gum acacia used in confectionery industry and in
baking industry
 Gum tragacanth is still a preffered ingredient ,
particularly used in conjunction with gum acacia
 Xanthan gum is a common suspending agent in
suspension for reconstitution

23. 2)CELLULOSE DERIVATIVES
Cellulose is one of the most widely used starting
material for manufacturing of modified natural
polymers.
Cellulose ethers with methyl substitution
generally form a gel at a elevated temperatures. Gel
formation is reversed when temperature is reduced.
CARBOXY METHYL CELLULOSE(CMC)
Sodium CMC ,an anionic polymer, is available in 3 grades.
 Food , pharmaceutical and technical

24.  It is also available with a variety of molecular weights
and degree of substitution
 CMC is more resistant to microbial attack than most
natural gums. The viscosity of CMC solution decreases
reversibly with increasing temperature
 The rheology of aqueous CMC solution depends on the
degree of substitution . Low substituted CMC products
exhibit thixotropy;higher substitution leads to
pseudoplastic behavior
 Use : suspending agent , emulsion stabilizer

25. ETHYL CELLULOSE
 It is a nonionic ether derivative of cellulose
 It is widely used as tablet binder ,thickening agent ,
coating material for tablets , microcapsules and
microparticles
HYDROXY ETHYL CELLULOSE(HEC)
 It is a nonionic cellulose ether
 Solutions of HEC exhibit pseudoplastic flow and have
no yield point

26. METHYL CELLULOSE & HYDROXY PROPYL
METHYL CELLULOSE (HPMC)
 Both are interesting examples , as they exhibit a reverse
thermal gelation , gelling when heated and melting when
cooled
 These are the nonionic cellulose ether derivatives
 Rheology of these solutions is pseudoplastic , and there
is no yield point
 Use : suspension stabilizer , thickener

27. Ionic Conc.
Agent charge pH Rheology Range
factor (%)
CMC Anionic Stable at Pseudo 1-2
pH 4-10 plastic
Ethyl Nonionic Stable at Pseudo 5
cellulose pH 4-10 Plastic
Hydroxy Nonionic Stable at Pseudo 0.3-2
propyl pH 4-10 Plastic
cellulose
HPMC Nonionic Stable at Pseudo 0.3-2
pH 4-11 Plastic
Methyl Nonionic Stable at Pseudo 1-5
cellulose pH 4-11 plastic

28. Applications of cellulose derivatives:
1.Methyl cellulose:
 Used in pharmaceutical gels
 High viscosity grades are used in opthalmic preparations
 Bulk forming laxative
 Lubricating jellies for surgical and medical procedures
2.HPMC:
 A 2 % solution is commercially available as an
opthalmic surgical aid

29. 3) MICROCRYSTALLINE CELLULOSE (MCC)
 Dispersions of MCC do not have viscosities that are
significantly greater than that of water. However ,
combinations of CMC,MC or HPMC are used to thicken
aqueous solutions
 The colloidal dispersions of MCC blends exhibit
thixotropic rheology , also exhibit a yield point
 Viscosity is not affected by temperature
 It is used as stabilizer and thickener in aqueous systems
 Formulation of dry powder suspension with MCC:alginate
complexes(0.5-10%w/w of total dry formulation)

30. 4) CHITOSAN
 Chitosan is a natural biopolymer derived from the outer
shell of crustaceans
 It is a weak cationic polysaccharide , biocompatible ,
biodegradable , nontoxic
 Unlike most gums , chitosan carries a positive charge
( at pH below 6.5 ) and is thus attracted to a variety of
biological tissues and surfaces that are negatively
charged

31. Uses:
 As permeation enhancer
 As mucoadhesive excipient
 It exhibits favourable biological behaviour , such as
bioadhesion and permeabilty enhancing properties ,
which make it a unique material for the design of ocular
drug delivery vehicles
 Enhanced bone formation by transforming growth factor
 Solubility increase as well as taste masking

32.  Useful in promoting tissue growth in tissue repair
 Accelerating wound-healing and bone regeneration
 Cholesterol lowering effects
5) SYNTHETIC POLYMERS
Carbomer ( polyacrylic acid )
 Solutions of carbomers are very pseudoplastic
 They exhibit a yield value
 It is an excellent choice as a thickener in creams and
lotions

33.  Carbomer 934P is the official name given to one
member of a acrylic polymers . Manufactured under the
trade name carbopol 934P , it is used as a thickening
agent in a variety of pharmaceutical and cosmetic
products
Polyvinylpyrrolidone ( PVP )
 Solutions are stable at elevated temperatures , but
viscosity drops reversibly with increasing temperature
 Use : in opthalmic preparations , serving as muco-
mimetic agent in arteficial tear formulations

34. 6) CLAYS
Magnesium aluminium silicate (veegum )
 The gels are formed at about 5% concentration.They
exhibit plastic flow
 It functions well as a suspending agent .
 It is a superior suspending agent because it prevents
caking without affecting pourability or spreadability of
suspension

35.  Magnesium aluminium silicate dispersions are
influenced by heat , and the viscosity of the dispersion
increases on prolonged exposure to elevated
temperatures
Attapulgite
 It is a magnesium aluminium silicate clay of very fine
particle size
 Use : Viscosity building , gelling , thickening agent ,
protective colloid , suspending agent , adsorbent ,
emulsion stabilizer

36. Bentonite
 It is a clay mineral of the smectite group
 It is an absorbent aluminium phyllosilicate , in general ,
impure clay consisting of montmorillonite
 The smectites are a group of minerals that swells as they
absorb water or organic molecules within the structural
layers
 It is prescribed as bulk laxative

37. Clays
Agent Rheology Conc.
Range(%)
Magnesium Plastic/ 0.5-5
aluminium thixotropy
silicate
Bentonite Plastic/ 1-6
thixotropy
Attapulgite Plastic/ 10
thixotropy

38. CONCLUSION
In pharmaceutical field , the viscosity promoters
play a vital role , as they stabilize the disperse systems and
also used in various dosage forms
Viscosity-inducing polymers should be used
with caution . They are known to form complexes with a
variety of organic and inorganic compounds

39. RECENT ADVANCES
 Sustained opthalmic delivery of ofloxacin from an
ion-activated in-situ gelling system (gelling agent is
sodium alginate in combination with hydroxy propyl
cellulose)
 To prolong precorneal residence time and to improve
bioavailability attempts were made to increase the
viscosity of the formulation using viscosity promoters
such as cellulose , poly alcohol and poly acrylic acid
 Chemically modified chitosan or its derivatives used in
delivering the bioactive molecules

40. REFERENCES
1.Herbert A. Lieberman , Martin M. Rieger and Gilbert S.
Banker ,Pharmaceutical Dosage Forms : Disperse systems
volume 1 , 2 & 3 (second Edition , Revised and Expanded )
2.James Swarbrick , Encyclopedia of pharmaceutical
technology , Third Edition
3.S Abraham , S Furtado , S Bharath , BV Basavaraj…
pak J Pharm…,2009-76.162.69.21
4.www.pharmainfo.net
5.www.sciencedirect.com
6.www.dallasmedication.com