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A SEMINAR ONVISCOSITY PROMOTERS     Presented by      Sushma.A     M.Pharmacy (I         sem)       Industrial
CONTENTS1.Introduction2.Ideal characteristics of viscosity promoters3.Classification        Natural gums        Cellulos...
INTRODUCTIONVISCOSITY:            Flow property of a simple liquid is expressed    in terms of viscosity. Quantitatively, ...
VISCOSITY PROMOTERS:             These are substances ,which added to anaqueous mixture, increase its viscosity withoutsub...
   Polymers are used in suspensions, emulsions , and    other dispersions ,primarily to minimize or control    sedimentat...
   Many polymers of natural origin are attacked directly by    microorganisms. Even if the polymer chosen is totally    r...
Advantages and Disadvantages due to viscosity of medium Advantages:     High viscosity inhibits the crystal growth.     ...
Disadvantages :   High viscosity hinders the re-dispersibility of the    sediments.   High viscosity retards the absorpt...
IDEAL CHARACTERISTICS OF VISCOSITY PROMOTERS:Should    produce a structured vehicleShould    have high viscosity at negl...
CLASSIFICATION:   Natural gums          Acacia , Tragacanth          Alginic acid           Karaya , Guar gum etc.,   Ce...
   Microcrystalline cellulose   Chitosan   Synthetic polymers        carbomer (polyacrylic acid)        polyvinyl pyrro...
1) NATURAL GUMS       Natural gums are polysaccharides of natural origin ,capable of causing a large viscosity increase in...
2.Natural gums obtained from non-marine          botanical    sources    Gum arabic (from the sap of acacia trees)    Gu...
3.Natural gums produced by bacterial fermentation        gellan gum        xanthan gumALGINATES   Anionic polysaccharide...
GUM ARABIC   Anionic polysaccharide   It is the dried exudate of trees of the genus acacia   Unlike most natural gums,a...
CARRAGEENAN   Anionic polysaccharide derived from seaweed   Solutions of carrageenan have a yield point when used    in ...
   Disadvantage of these gels is the presence of insoluble    plant residue   Use: thickener , suspension stabilizerKARA...
LOCUST BEAN GUM   Nonionic seed polysaccharide   Solutions of this gum are psuedoplastic   It is one of the more effici...
XANTHAN GUM   Anionic polysaccharide   Exhibits pseudoplastic rheology   Temperature has very little effect on the visc...
Properties of Selected Viscosity-Imparting AgentsAgent     Structure Ionic         pH factors Rheology                    ...
Agent        Structure Ionic       pH             Rheology                       charge      factorsGum           Poly    ...
Applications of natural gums:   Guar gum is a colon- specific drug delivery carrier is    based on its degradation by col...
2)CELLULOSE DERIVATIVES          Cellulose is one of the most widely used starting    material for manufacturing of modifi...
   It is also available with a variety of molecular weights    and degree of substitution   CMC is more resistant to mic...
ETHYL CELLULOSE   It is a nonionic ether derivative of cellulose   It is widely used as tablet binder ,thickening agent ...
METHYL CELLULOSE & HYDROXY PROPYL    METHYL CELLULOSE (HPMC)   Both are interesting examples , as they exhibit a reverse ...
Ionic                         Conc.Agent       charge   pH          Rheology Range                     factor             ...
Applications of cellulose derivatives:1.Methyl cellulose:   Used in pharmaceutical gels   High viscosity grades are used...
3) MICROCRYSTALLINE CELLULOSE (MCC)   Dispersions of MCC do not have viscosities that are    significantly greater than t...
4) CHITOSAN   Chitosan is a natural biopolymer derived from the outer    shell of crustaceans   It is a weak cationic po...
Uses:   As permeation enhancer   As mucoadhesive excipient   It exhibits favourable biological behaviour , such as    b...
   Useful in promoting tissue growth in tissue repair   Accelerating wound-healing and bone regeneration   Cholesterol ...
   Carbomer 934P is the official name given to one    member of a acrylic polymers . Manufactured under the    trade name...
6) CLAYSMagnesium aluminium silicate (veegum )   The gels are formed at about 5% concentration.They    exhibit plastic fl...
   Magnesium aluminium silicate dispersions are    influenced by heat , and the viscosity of the dispersion    increases ...
Bentonite   It is a clay mineral of the smectite group   It is an absorbent aluminium phyllosilicate , in general ,    i...
Clays  Agent        Rheology    Conc.                           Range(%)Magnesium     Plastic/       0.5-5aluminium     th...
CONCLUSION          In pharmaceutical field , the viscosity promotersplay a vital role , as they stabilize the disperse sy...
RECENT ADVANCES Sustained    opthalmic delivery of ofloxacin from an  ion-activated in-situ gelling system (gelling agent...
REFERENCES 1.Herbert A. Lieberman , Martin M. Rieger and Gilbert S.Banker ,Pharmaceutical Dosage Forms : Disperse systemsv...
Viscosity promoters
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Viscosity promoters

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Viscosity promoters

  1. 1. A SEMINAR ONVISCOSITY PROMOTERS Presented by Sushma.A M.Pharmacy (I sem) Industrial
  2. 2. CONTENTS1.Introduction2.Ideal characteristics of viscosity promoters3.Classification  Natural gums  Cellulose derivatives  Microcrystalline cellulose  Chitosan  Synthetic polymers  Clays4. Conclusion References
  3. 3. INTRODUCTIONVISCOSITY: 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. 4. VISCOSITY PROMOTERS: These are substances ,which added to anaqueous mixture, increase its viscosity withoutsubstantially modifying its other properties , such as taste.They provide body, increase stability , and improvesuspension of added ingredients. It is desirable to increase the viscosity of liquid toprovide or to improve palatability or pourability
  5. 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. 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. 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. 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. 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. 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. 11.  Microcrystalline cellulose Chitosan Synthetic polymers carbomer (polyacrylic acid) polyvinyl pyrrolidone polyvinyl alcohol Clays Magnesium aluminium silicate(veegum) Bentonite , Attapulgite
  12. 12. 1) NATURAL GUMS Natural gums are polysaccharides of natural origin ,capable of causing a large viscosity increase in solution ,evenat small concentrationsThese 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. 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. 14. 3.Natural gums produced by bacterial fermentation gellan gum xanthan gumALGINATES 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. 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. 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 stabilizerGUAR GUM Nonionic polysacccharide derived from seeds It exhibits pseudoplastic flow
  17. 17.  Disadvantage of these gels is the presence of insoluble plant residue Use: thickener , suspension stabilizerKARAYA 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. 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 gumsTRAGACANTH GUM Anionic polysaccharide It exhibit pseudoplastic flow It is one of the most efficient natural polymer thickeners
  19. 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. 20. Properties of Selected Viscosity-Imparting AgentsAgent Structure Ionic pH factors Rheology chargeAlginates 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. 21. Agent Structure Ionic pH Rheology charge factorsGum Poly anionic Stable at Pseudotragacanth saccharide pH 1.9-8.5 plasticXanthan Poly anionic Good Pseudogum saccharide stability at plastic pH 1-12Locust Poly Pseudobean gum saccharide nonionic --- plasticGuar gum Poly anionic Stable at Pseudo saccharide pH 4-10 plastic
  22. 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. 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. 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. 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 microparticlesHYDROXY ETHYL CELLULOSE(HEC) It is a nonionic cellulose ether Solutions of HEC exhibit pseudoplastic flow and have no yield point
  26. 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. 27. Ionic Conc.Agent charge pH Rheology Range factor (%)CMC Anionic Stable at Pseudo 1-2 pH 4-10 plasticEthyl Nonionic Stable at Pseudo 5cellulose pH 4-10 PlasticHydroxy Nonionic Stable at Pseudo 0.3-2propyl pH 4-10 PlasticcelluloseHPMC Nonionic Stable at Pseudo 0.3-2 pH 4-11 PlasticMethyl Nonionic Stable at Pseudo 1-5cellulose pH 4-11 plastic
  28. 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 procedures2.HPMC: A 2 % solution is commercially available as an opthalmic surgical aid
  29. 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. 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. 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. 32.  Useful in promoting tissue growth in tissue repair Accelerating wound-healing and bone regeneration Cholesterol lowering effects5) SYNTHETIC POLYMERSCarbomer ( 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. 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 productsPolyvinylpyrrolidone ( 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. 34. 6) CLAYSMagnesium 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. 35.  Magnesium aluminium silicate dispersions are influenced by heat , and the viscosity of the dispersion increases on prolonged exposure to elevated temperaturesAttapulgite 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. 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. 37. Clays Agent Rheology Conc. Range(%)Magnesium Plastic/ 0.5-5aluminium thixotropysilicateBentonite Plastic/ 1-6 thixotropyAttapulgite Plastic/ 10 thixotropy
  38. 38. CONCLUSION In pharmaceutical field , the viscosity promotersplay a vital role , as they stabilize the disperse systems andalso used in various dosage forms Viscosity-inducing polymers should be usedwith caution . They are known to form complexes with avariety of organic and inorganic compounds
  39. 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. 40. REFERENCES 1.Herbert A. Lieberman , Martin M. Rieger and Gilbert S.Banker ,Pharmaceutical Dosage Forms : Disperse systemsvolume 1 , 2 & 3 (second Edition , Revised and Expanded )2.James Swarbrick , Encyclopedia of pharmaceuticaltechnology , Third Edition3.S Abraham , S Furtado , S Bharath , BV Basavaraj…pak J Pharm…,2009-76.162.69.214.www.pharmainfo.net5.www.sciencedirect.com6.www.dallasmedication.com

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