Organogels.

ORGANOGELORGANOGEL
Presented by:
Chinchole Pravin Sonu
(M.PHARM 2nd
SEM)
DEPARTMENT OF PHARMACEUTICS &
QUALITY ASSURANCE
R. C. Patel Institute of
Pharmaceutical Education and
Research, shirpur.

CONTENTSCONTENTS
 IntroductionIntroduction
 Types Of OrganogelTypes Of Organogel
 Organogels In Drug DeliveryOrganogels In Drug Delivery
 Characterisation Of OrganogelCharacterisation Of Organogel
 Area Of ApplicationArea Of Application
 ApplicationsApplications
 ConclusionConclusion
 ReferenceReference

INTRODUCTIONINTRODUCTION
 In the last decade, interest in organogels has grown rapidly withIn the last decade, interest in organogels has grown rapidly with
the discovery and synthesis of a very large number of diversethe discovery and synthesis of a very large number of diverse
molecules, which can gel organic solvents at low concentrations.molecules, which can gel organic solvents at low concentrations.
 A simple working definition of the term ‘gel’ is a soft, solid orA simple working definition of the term ‘gel’ is a soft, solid or
solid-like material, which contains both solid and liquidsolid-like material, which contains both solid and liquid
components, where the solid component (the gelator) is present ascomponents, where the solid component (the gelator) is present as
a mesh/network of aggregates, which immobilises the liquida mesh/network of aggregates, which immobilises the liquid
component. This solid network prevents the liquid from flowing,component. This solid network prevents the liquid from flowing,
primarily via surface tension.primarily via surface tension.

 The gel is said to be a hydrogel or an organogel depending on theThe gel is said to be a hydrogel or an organogel depending on the
nature of the liquid component: water in hydrogels and an organicnature of the liquid component: water in hydrogels and an organic
solvent in organogels.solvent in organogels.
 However, only a few organogels are currently being studied as drugHowever, only a few organogels are currently being studied as drug
delivery vehicles as most of the existing organogels are composeddelivery vehicles as most of the existing organogels are composed
of pharmaceutically unacceptable organic liquids and/orof pharmaceutically unacceptable organic liquids and/or
unacceptable/untested gelators.unacceptable/untested gelators.
 In this seminar a brief overview of organogels is presented,In this seminar a brief overview of organogels is presented,
followed by a more in-depth review of the gels that have beenfollowed by a more in-depth review of the gels that have been
investigated for drug delivery.investigated for drug delivery.

OrganogelOrganogel
 Gel is a soft solid which contains both solid & liquid components where theGel is a soft solid which contains both solid & liquid components where the
solid component( the gelator) is present as a mesh/network of aggregates,solid component( the gelator) is present as a mesh/network of aggregates,
which immobilizes the liquid componentwhich immobilizes the liquid component
 The solid network prevents the liquid from flowingThe solid network prevents the liquid from flowing
 The gel is called as hydrogel or organogel depending on the nature of the liquidThe gel is called as hydrogel or organogel depending on the nature of the liquid
component( water in hydrogels & an organic solvent in organogelscomponent( water in hydrogels & an organic solvent in organogels
 In hydrogels the gelator is a polymer while in case of organogel, gelators areIn hydrogels the gelator is a polymer while in case of organogel, gelators are
small moleculessmall molecules

OrganogelatorsOrganogelators
 n-alkanes such as hexadecane & organic liquidsn-alkanes such as hexadecane & organic liquids
 Non ionic surfactant- sorbitan monostearateNon ionic surfactant- sorbitan monostearate
 Steroids & their derivativesSteroids & their derivatives
 Anthranyl derivativesAnthranyl derivatives
 Macrocyclic gelators (calixarenes)Macrocyclic gelators (calixarenes)

Gel preparationGel preparation
 Most of the organogels are prepared by heating a mixture of the gelator &Most of the organogels are prepared by heating a mixture of the gelator &
the liquid component to form organic solution/dispersionthe liquid component to form organic solution/dispersion
 Heating allows dissolution of gelator in the liquidHeating allows dissolution of gelator in the liquid
 Following cooling, the solubility of gelator in the liquid phase decreases &Following cooling, the solubility of gelator in the liquid phase decreases &
gelator-solvent interactions are reduced, which results in gelator moleculesgelator-solvent interactions are reduced, which results in gelator molecules
coming out of solutioncoming out of solution
 Entanglement of the aggregates & connections among them result in theEntanglement of the aggregates & connections among them result in the
formation of three dimensional network, which immobilizes the fluid phaseformation of three dimensional network, which immobilizes the fluid phase
 The physical organogels, held together by noncovalent forces areThe physical organogels, held together by noncovalent forces are
thermoreversiblethermoreversible

 Following heating the gel melts to the sol phase as the gelator aggregatesFollowing heating the gel melts to the sol phase as the gelator aggregates
dissolve in the organic liquid, whereas cooling the hot sol phase results indissolve in the organic liquid, whereas cooling the hot sol phase results in
gelationgelation
 The temperature at which the sol-to-gel or gel-to-sol transition occurs isThe temperature at which the sol-to-gel or gel-to-sol transition occurs is
called the gelation temp.called the gelation temp.
 TheThe TgTg of 10% w/v sorbitan monostearate isof 10% w/v sorbitan monostearate is 41-4441-4400
CC
 Solutions of lecithin in an organic solvent such as iso-octane can be gelledSolutions of lecithin in an organic solvent such as iso-octane can be gelled
by the addition of trace amounts of a polar substance e.g. water ,glycerol,by the addition of trace amounts of a polar substance e.g. water ,glycerol,
ethylene glycol or formamideethylene glycol or formamide

Organogel structure & mechanism of organogellingOrganogel structure & mechanism of organogelling
 The organogelling or gelation of lecithin solutions in organicThe organogelling or gelation of lecithin solutions in organic
solvents is induced as a result of incorporation of a polarsolvents is induced as a result of incorporation of a polar
solventsolvent
 Lecithin when dissolved in nonpolar media alone , selfLecithin when dissolved in nonpolar media alone , self
assembles into reverse micelles.assembles into reverse micelles.
 The growth of spherical reverse micelles & furtherThe growth of spherical reverse micelles & further
transformation into tubular & cylindrical micellar aggregatestransformation into tubular & cylindrical micellar aggregates
(sphere to cylinder transformation) is triggered by addition of(sphere to cylinder transformation) is triggered by addition of
small & critical amounts of polar additivesmall & critical amounts of polar additive

 The specific process leading to the formation of the gelling matrix depends on theThe specific process leading to the formation of the gelling matrix depends on the
physicochemical properties of gel components and their resulting interactions.physicochemical properties of gel components and their resulting interactions. Figure 1Figure 1
presents a flow-chart compiling various accepted classifications of gels based on thepresents a flow-chart compiling various accepted classifications of gels based on the
nature of solvents, gelators, and intermolecular interactions.nature of solvents, gelators, and intermolecular interactions.

TYPES OF ORGANOGELTYPES OF ORGANOGEL
 Sorbitan Monostearate OrganogelsSorbitan Monostearate Organogels
 In Situ Formation Of An Organogel Of L-alanine DerivativeIn Situ Formation Of An Organogel Of L-alanine Derivative
 Eudragit OrganogelsEudragit Organogels
 Microemulsion-based GelsMicroemulsion-based Gels
 Lecithin OrganogelsLecithin Organogels
 Pluronic Lecithin OrganogelsPluronic Lecithin Organogels

Sorbitan Monostearate OrganogelsSorbitan Monostearate Organogels
 Sorbitan monostearateSorbitan monostearate (Span 60)(Span 60) and sorbitan monopalmitateand sorbitan monopalmitate (Span 40)(Span 40)
have been found to gel a number of organic solvents at low concentrations.have been found to gel a number of organic solvents at low concentrations.
They are prepared byThey are prepared by heating the gelator/liquid mixtureheating the gelator/liquid mixture in a water bathin a water bath
at 60°C (which results in dispersion of the gelator in the liquid medium)at 60°C (which results in dispersion of the gelator in the liquid medium)
andand coolingcooling of the resulting suspension, following which the latter sets toof the resulting suspension, following which the latter sets to
an opaque, white,an opaque, white, semisolid gel.semisolid gel.
 Sorbitan monostearate molecules are arranged in inverted bilayers withinSorbitan monostearate molecules are arranged in inverted bilayers within
the tubules, as shown inthe tubules, as shown in Figure.Figure.

 The tubules form a three-dimensional network, which immobilizes the liquid, and henceThe tubules form a three-dimensional network, which immobilizes the liquid, and hence
a gel is formed.a gel is formed.
 Sorbitan monostearate gels has been investigated as delivery vehicles for hydrophilicSorbitan monostearate gels has been investigated as delivery vehicles for hydrophilic
vaccinesvaccines

In Situ Formation Of An Organogel Of L-alanine DerivativeIn Situ Formation Of An Organogel Of L-alanine Derivative
 In situ L-alanine derivative organogel is prepared from N-lauroyl-L-alanineIn situ L-alanine derivative organogel is prepared from N-lauroyl-L-alanine
methyl ester (LAM) which gels in the pharmaceutically acceptable organicmethyl ester (LAM) which gels in the pharmaceutically acceptable organic
solvents such as soybean oil and medium-chain triglycerides.solvents such as soybean oil and medium-chain triglycerides.
 Normally, the system exists in the gel state at room temperature but on theNormally, the system exists in the gel state at room temperature but on the
addition of ethanol to a gelator/solvent solution it inhibits gelation because theaddition of ethanol to a gelator/solvent solution it inhibits gelation because the
ethanol disrupts the formation of hydrogen bonds (essential for gelator self-ethanol disrupts the formation of hydrogen bonds (essential for gelator self-
assembly into aggregates) between the gelator molecules. This means that aassembly into aggregates) between the gelator molecules. This means that a
solution of LAM in an organic solvent can remain in the sol phase at roomsolution of LAM in an organic solvent can remain in the sol phase at room
temperature when some ethanol is added to the mixture.temperature when some ethanol is added to the mixture.
 When such a sol phase (20% LAM plus 14% ethanol in soybean oil) wasWhen such a sol phase (20% LAM plus 14% ethanol in soybean oil) was
placed in phosphate buffered saline at 37°C it turned into an opaque gel withinplaced in phosphate buffered saline at 37°C it turned into an opaque gel within
2 min as the hydrophilic ethanol diffused away into the aqueous buffer, and as2 min as the hydrophilic ethanol diffused away into the aqueous buffer, and as
gelator–gelator hydrogen bonds were formed.gelator–gelator hydrogen bonds were formed.

 Thus, theoretically, such a LAM/ethanol/soybean oil solution could form gels in situThus, theoretically, such a LAM/ethanol/soybean oil solution could form gels in situ
following its subcutaneous injection, due to ethanol diffusion away from thefollowing its subcutaneous injection, due to ethanol diffusion away from the
formulation, into the surrounding tissues.formulation, into the surrounding tissues.
 The main advantage of in situ forming gels is their injectability at room temperature.The main advantage of in situ forming gels is their injectability at room temperature.
Once a drug-containing gel is formed in situ, it could act as a sustained-release implantOnce a drug-containing gel is formed in situ, it could act as a sustained-release implant

Eudragit OrganogelEudragit Organogel
 Eudragit organogels are different from the organogels they are the mixtures of Eudragit (LEudragit organogels are different from the organogels they are the mixtures of Eudragit (L
or S) and polyhydric alcohols, such as glycerol, propylene glycol and liquid polyethyleneor S) and polyhydric alcohols, such as glycerol, propylene glycol and liquid polyethylene
glycol, containing high concentrations (30 or 40% w/w) of Eudragit.glycol, containing high concentrations (30 or 40% w/w) of Eudragit.
 Drug-containing gels were prepared by dissolving the drug (salicylic acid, sodiumDrug-containing gels were prepared by dissolving the drug (salicylic acid, sodium
salicylate, procain or ketoprofen) in propylene glycol, pouring the resulting solution intosalicylate, procain or ketoprofen) in propylene glycol, pouring the resulting solution into
Eudragit powder (contained in a mortar), and immediately mixing with a pestle for 1 min.Eudragit powder (contained in a mortar), and immediately mixing with a pestle for 1 min.
 Gel viscosity was found to increase with increasing concentrations of Eudragit and toGel viscosity was found to increase with increasing concentrations of Eudragit and to
decrease with increasing drug content. The drug content in Eudragit organogels should bedecrease with increasing drug content. The drug content in Eudragit organogels should be
kept low (e.g., 1.25% w/w) to maintain gel rigidity and stability.kept low (e.g., 1.25% w/w) to maintain gel rigidity and stability.
 The mechanism of drug release from Eudragit L and S organogels was due to surfaceThe mechanism of drug release from Eudragit L and S organogels was due to surface
erosion of the Eudragit L and diffusion through the Eudragit S gel matrix.erosion of the Eudragit L and diffusion through the Eudragit S gel matrix.
 Drug release from Eudragit S organogel thus increased with increasing temperature andDrug release from Eudragit S organogel thus increased with increasing temperature and
agitation rate of the release medium.agitation rate of the release medium.

Microemulsion-based GelsMicroemulsion-based Gels
 Microemulsion-based gels (MBGs) are also different from most organogels in that theMicroemulsion-based gels (MBGs) are also different from most organogels in that the
gelator, gelatin, is a hydrophilic polymer, which gels water.gelator, gelatin, is a hydrophilic polymer, which gels water.
 MBGs were initially prepared by dissolving solid gelatin in a hot w/o microemulsionMBGs were initially prepared by dissolving solid gelatin in a hot w/o microemulsion
(which was composed of water, AOT and isooctane) followed by cooling.(which was composed of water, AOT and isooctane) followed by cooling.
 In MBGs, the gelatin would dissolve in the water droplets of the w/o microemulsion andIn MBGs, the gelatin would dissolve in the water droplets of the w/o microemulsion and
that cooling of the system would result in gelation of the water droplets, which wouldthat cooling of the system would result in gelation of the water droplets, which would
lead to clouding of the system and possibly phase separation. Thus microemulsion gelledlead to clouding of the system and possibly phase separation. Thus microemulsion gelled
to a transparent semisolid with a high viscosity and a high electro-conductivity.to a transparent semisolid with a high viscosity and a high electro-conductivity.

Lecithin OrganogelsLecithin Organogels
 Lecithin Organogels (Los) are thermodynamically stable, clear, viscoelastic,Lecithin Organogels (Los) are thermodynamically stable, clear, viscoelastic,
biocompatible, and isotropic gels composed of phospholipids (lecithin),biocompatible, and isotropic gels composed of phospholipids (lecithin),
appropriate organic solvent, and a polar solventappropriate organic solvent, and a polar solvent
 LOs, the jelly-like phases, consist of a 3-dimensional network of entangledLOs, the jelly-like phases, consist of a 3-dimensional network of entangled
reverse cylindrical (polymer-like) micelles, which immobilizes the continuous orreverse cylindrical (polymer-like) micelles, which immobilizes the continuous or
macroscopic external organic phase, thus turning a liquid into a gel.macroscopic external organic phase, thus turning a liquid into a gel.
 A lecithin organogel is formed when small amounts of water or other polarA lecithin organogel is formed when small amounts of water or other polar
substances, such as glycerol, ethylene glycol or formamide, are added to asubstances, such as glycerol, ethylene glycol or formamide, are added to a
nonaqueous solution of lecithin.nonaqueous solution of lecithin.
 The molar ratio of water to lecithin (w0 = [H2O]/[lecithin]) is typically 2:10 andThe molar ratio of water to lecithin (w0 = [H2O]/[lecithin]) is typically 2:10 and
depends on the nature of the organic solvent. Excess water leads to destabilizationdepends on the nature of the organic solvent. Excess water leads to destabilization
of the gel and phase separation.of the gel and phase separation.
 Lecithin organogels have been used as carriers for hydrophilic and hydrophobicLecithin organogels have been used as carriers for hydrophilic and hydrophobic
drug molecules. Hydrophobic drugs are dissolved in the oil phase (lecithin plusdrug molecules. Hydrophobic drugs are dissolved in the oil phase (lecithin plus
organic solvent), whereas hydrophilic molecules are dissolved in water, which isorganic solvent), whereas hydrophilic molecules are dissolved in water, which is
then added to an organic solution of lecithin to induce gelation.then added to an organic solution of lecithin to induce gelation.

 Soy or egg lecithin in the conc. range of 50-200 mM in different organicSoy or egg lecithin in the conc. range of 50-200 mM in different organic
solvents such as linear or cyclic alkanes, esters of fatty acids & amides wassolvents such as linear or cyclic alkanes, esters of fatty acids & amides was
noted to be effective for gel formationnoted to be effective for gel formation
 It was observed that addition of trace amounts of water into nonaqueousIt was observed that addition of trace amounts of water into nonaqueous
solutions of soy lecithin(50-200 mM) caused an abrupt rise insolutions of soy lecithin(50-200 mM) caused an abrupt rise in
viscosity(10viscosity(1044
-10-1066
times)times)
 The transfer of jelly like state has been demonstrated only for nonaqueousThe transfer of jelly like state has been demonstrated only for nonaqueous
solutions of naturally occuring unsaturated lecithinssolutions of naturally occuring unsaturated lecithins
 Synthetic lecithins containing residues of saturated fatty acids failed toSynthetic lecithins containing residues of saturated fatty acids failed to
form organogel. Lecithin should contain 95% phosphatidylcholineform organogel. Lecithin should contain 95% phosphatidylcholine
 Organic solvents which have gelling property are fatty acids& amines,Organic solvents which have gelling property are fatty acids& amines,
ethyl myristate, IPM,IPP (biocompatible, biodegradable,skin penetrationethyl myristate, IPM,IPP (biocompatible, biodegradable,skin penetration
enhancing property), ethers & esters, cyclopentane, linear,branched,&enhancing property), ethers & esters, cyclopentane, linear,branched,&
cyclic alkanescyclic alkanes

Figure 1. Schematic diagram of the preparation of lecithin organogels.
Note: Lipophilic drugs are solubilized in the organic phase (stage 1), whereas
hydrophilic compounds can be solubilized in the polar phase (stage 2). For the
preparation of pluronic lecithin organogel (PLO gel), the co-surfactant pluronic is taken
along with polar phase (stage 2).

Table 1.Table 1. Various Salient Features of Lecithin OrganogelsVarious Salient Features of Lecithin Organogels
Salient FeaturesSalient Features
Template vehicleTemplate vehicle LOs provide opportunities for incorporation of a wide range ofLOs provide opportunities for incorporation of a wide range of
substances with diverse physicochemical characters (e.g. chemicalsubstances with diverse physicochemical characters (e.g. chemical
nature, solubility, molecular weight, size)nature, solubility, molecular weight, size)
Process benefitsProcess benefits Spontaneity of organogel formation, by virtue of self-assembledSpontaneity of organogel formation, by virtue of self-assembled
supramolecular arrangement of surfactant molecules, makes thesupramolecular arrangement of surfactant molecules, makes the
process very simple and easy to handle.process very simple and easy to handle.
Structural/physicalStructural/physical
stabilitystability
Being thermodynamically stable, the structural integrity of LOs isBeing thermodynamically stable, the structural integrity of LOs is
maintained for longer time periods.maintained for longer time periods.
Chemical stabilityChemical stability LOs are moisture insensitive, and being organic in character, they alsoLOs are moisture insensitive, and being organic in character, they also
resist microbial contamination.resist microbial contamination.
Topical deliveryTopical delivery
potentialpotential
 Being well balanced in hydrophilic and lipophilic character, theyBeing well balanced in hydrophilic and lipophilic character, they
can efficiently partition with the skin and therefore enhance the skincan efficiently partition with the skin and therefore enhance the skin
penetration and transport of the molecules.penetration and transport of the molecules.
 LOs also provide the desired hydration of skin in a lipid-enrichedLOs also provide the desired hydration of skin in a lipid-enriched
environment so as to maintain the bioactive state of skin.environment so as to maintain the bioactive state of skin.
SafetySafety Use of biocompatible, biodegradable, and non immunogenic materialsUse of biocompatible, biodegradable, and non immunogenic materials
makes them safe for long term applications.makes them safe for long term applications.

Pluronic Lecithin OrganogelsPluronic Lecithin Organogels
 PLO is an opaque, yellow gel, composed of isopropyl palmitate, soyPLO is an opaque, yellow gel, composed of isopropyl palmitate, soy
lecithin, water and the hydrophilic polymer, Pluronic F127. The differencelecithin, water and the hydrophilic polymer, Pluronic F127. The difference
between PLO and its precursor, lecithin gels, is the presence of Pluronicbetween PLO and its precursor, lecithin gels, is the presence of Pluronic
F127 (a hydrophilic polymer that gels water) and the greater amount ofF127 (a hydrophilic polymer that gels water) and the greater amount of
water compared with the oil.water compared with the oil.
 PLO gel looks and feels like a cream but is actually a gel. When thePLO gel looks and feels like a cream but is actually a gel. When the
aqueous phase (pluronic gel) is combined with the lecithin oil base createsaqueous phase (pluronic gel) is combined with the lecithin oil base creates
an emulsion that forms together due to the pluronic gel and the viscosity ofan emulsion that forms together due to the pluronic gel and the viscosity of
that gel at room temperature.that gel at room temperature.

 PLO has been shown in vivo and in vitro to modulate thePLO has been shown in vivo and in vitro to modulate the
release and permeation of drugs applied transdermally.release and permeation of drugs applied transdermally.
 It improves the topical administration of drug mainly due toIt improves the topical administration of drug mainly due to
the desired drug partitioning, biphasic drug solubility and thethe desired drug partitioning, biphasic drug solubility and the
modification of skin barrier system by organogel components.modification of skin barrier system by organogel components.
 It shows low skin irritation, increases patient compliance,It shows low skin irritation, increases patient compliance,
reduces side effects, avoids first pass metabolism andreduces side effects, avoids first pass metabolism and
increases efficiency of drug.increases efficiency of drug.

Organogels In Drug DeliveryOrganogels In Drug Delivery
 Despite the large abundance and variety of organogel systems, relatively fewDespite the large abundance and variety of organogel systems, relatively few
have current applications in drug delivery, owing mostly to the lack ofhave current applications in drug delivery, owing mostly to the lack of
information on the biocompatibility and toxicity of organogelator moleculesinformation on the biocompatibility and toxicity of organogelator molecules
and their degradation products. This review focuses on organogel systemsand their degradation products. This review focuses on organogel systems
that have been geared towards pharmaceutical applications and are atthat have been geared towards pharmaceutical applications and are at
various stages of development, from preliminary in vitro experiments tovarious stages of development, from preliminary in vitro experiments to
clinical studies.clinical studies.
Table ITable I provides a summary of the key drug delivery studies conductedprovides a summary of the key drug delivery studies conducted
using organogels.using organogels.

Table I: Organogel Formulations Used In Drug DeliveryTable I: Organogel Formulations Used In Drug Delivery
Sr.No.Sr.No. TypesTypes Route ofRoute of
administrationadministration
Study conductedStudy conducted Model drugsModel drugs
11 LecithinLecithin TransdermalTransdermal  Clinical trialsClinical trials
 In vivo skinIn vivo skin
permeation & efficacypermeation & efficacy
 In vitro skinIn vitro skin
PermeationPermeation
 In vitro releaseIn vitro release
 DiclofenacDiclofenac
 Piroxicam, tetrabenzamidinePiroxicam, tetrabenzamidine
 Scopolamine and boxaterolScopolamine and boxaterol
Propranolol, nicardipinePropranolol, nicardipine
 Aceclofenac, indomethacin &Aceclofenac, indomethacin &
DiclofenacDiclofenac
22 SorbitanSorbitan
monostearatemonostearate
(SMS)(SMS)
 NasalNasal
 OralOral
 Subcutaneous &Subcutaneous &
intramuscularintramuscular
 In vivo efficacyIn vivo efficacy
 PropranololPropranolol
 Cyclosporin ACyclosporin A
 BSABSA11
and HAand HA22
33 PLOsPLOs TransdermalTransdermal  Clinical trialsClinical trials
 In vivo skin permeationIn vivo skin permeation
& efficacy& efficacy
Promethazine, Ondansetron &Promethazine, Ondansetron &
DiclofenacDiclofenac
Methimazole, Fluoxetine,Methimazole, Fluoxetine,
Dexamethazone, Amitriptyline,Dexamethazone, Amitriptyline,
Methadone, Morphine,Methadone, Morphine,
Buprenorphine & BuspironeBuprenorphine & Buspirone
Scopolamine, Metoclopramide,Scopolamine, Metoclopramide,
Haloperidol & ProchlorperazineHaloperidol & Prochlorperazine

Sr.NoSr.No TypesTypes Route ofRoute of
administrationadministration
Study conductedStudy conducted Model drugsModel drugs
44 L-alanineL-alanine
derivativederivative
SubcutaneousSubcutaneous  In vitro/in vivoIn vitro/in vivo
releaserelease
 In vitro/in vivoIn vitro/in vivo
releaserelease
and efficacyand efficacy
 RivastigmineRivastigmine
 LeuprolideLeuprolide
55 EudragitEudragit
organogesorganoges
 RectalRectal
 BuccalBuccal
 Salicylic acidSalicylic acid
 BSABSA

Characterization Of OrganogelsCharacterization Of Organogels
 In contrast to the ease of preparation, characterization of organogels isIn contrast to the ease of preparation, characterization of organogels is
relatively complicated on account of their interior structural design build-uprelatively complicated on account of their interior structural design build-up
on the self-associated supramolecules.on the self-associated supramolecules.
 These microstructures, the result of varied polar-nonpolar interactions, areThese microstructures, the result of varied polar-nonpolar interactions, are
highly sensitive and pose difficulties in the investigative studies. However,highly sensitive and pose difficulties in the investigative studies. However,
different characterization studies are extremely useful while investigating thedifferent characterization studies are extremely useful while investigating the
potential applications of organogel systems as a topical vehicle.potential applications of organogel systems as a topical vehicle.
 It has been reported that many of the physicochemical properties ofIt has been reported that many of the physicochemical properties of
organogels viz Rheological behavior, physical and mechanical stability andorganogels viz Rheological behavior, physical and mechanical stability and
drug release behavior are dependent upon how molecules arrange themselvesdrug release behavior are dependent upon how molecules arrange themselves
to provide the specific structural network within the organogel system.to provide the specific structural network within the organogel system.

 Gelation StudiesGelation Studies
 Rheological BehaviorRheological Behavior
 Structural FeaturesStructural Features
 Phase Transition TemperaturesPhase Transition Temperatures
 Gel StrengthGel Strength
 Water ContentWater Content
 Percentage Drug ContentPercentage Drug Content
 In-vitro / Permeation StudyIn-vitro / Permeation Study
 In-vivo StudyIn-vivo Study
 Stability StudyStability Study
Evaluation Of OrganogelsEvaluation Of Organogels

 Gelation StudiesGelation Studies:-A simple visual test to determine whether:-A simple visual test to determine whether
gelation has taken place involves inverting the reactiongelation has taken place involves inverting the reaction
vessel,gelation has occurred if the sample does not flowvessel,gelation has occurred if the sample does not flow
 Rheological BehaviorRheological Behavior:- are viscoelastic in nature, prior to:- are viscoelastic in nature, prior to
gelling exhibit Newtonian behavior & follows viscoelasticgelling exhibit Newtonian behavior & follows viscoelastic
behavior on addition of polar phase. It has been observed thatbehavior on addition of polar phase. It has been observed that
increasing the gelator conc. leads to increase in the viscosity &increasing the gelator conc. leads to increase in the viscosity &
hence gel strengthhence gel strength
 Structural featuresStructural features:-Molecular architecture of organogels has:-Molecular architecture of organogels has
been evaluated using NMR spectroscopy, hydrogen bondingbeen evaluated using NMR spectroscopy, hydrogen bonding
has been established by FTIR spectroscopy. The knowledge ofhas been established by FTIR spectroscopy. The knowledge of
molecular packing within organogel network has beenmolecular packing within organogel network has been
obtained using scanning & transmission electron microscopyobtained using scanning & transmission electron microscopy

 Phase transition Temperature:-Phase transition Temperature:- gives insight into the nature ofgives insight into the nature of
microstructures that form the gelling cross linked network. A narrow PTTmicrostructures that form the gelling cross linked network. A narrow PTT
range(3-5range(3-500
C) is indicative of homogeneous microstructures within the gel.C) is indicative of homogeneous microstructures within the gel.
It is determined by hot stage microscopy (HST)& high sensitivity DCSIt is determined by hot stage microscopy (HST)& high sensitivity DCS
 Gel strength:-Gel strength:-
 Water ContentWater Content:-water loss by evaporation can lead to decrease in viscisity:-water loss by evaporation can lead to decrease in viscisity
thus affecting the gel stability. Near infrared spectroscopy(NIR,1800-2200)thus affecting the gel stability. Near infrared spectroscopy(NIR,1800-2200)
is used for determining water contentis used for determining water content

Area Of ApplicationArea Of Application
 The site of application can drastically affect the distributionThe site of application can drastically affect the distribution
and absorption of a drug.and absorption of a drug.
 If a systemic effect is desired, the gel should be applied toIf a systemic effect is desired, the gel should be applied to
neck, inner thigh, or inner wrist area.neck, inner thigh, or inner wrist area.
 For a local effect, the gel should be applied directly to the jointFor a local effect, the gel should be applied directly to the joint
or painful region, then rub in wellor painful region, then rub in well

ApplicationApplication
 Ease of preparation & scale up, easier quality monitoring, thermodynamicEase of preparation & scale up, easier quality monitoring, thermodynamic
stability, enhanced topical performance, biocompatibility, safety uponstability, enhanced topical performance, biocompatibility, safety upon
applications for prolonged period make the organogels a vehicle of choice forapplications for prolonged period make the organogels a vehicle of choice for
topical drug deliverytopical drug delivery
 Ease of administration.Ease of administration.
 Site specific drug delivery.Site specific drug delivery.
 Avoids first pass effect.Avoids first pass effect.
 Absorption enhancement.Absorption enhancement.
 Overcome the problems of conventional dosage forms.Overcome the problems of conventional dosage forms.

LimitationLimitation
 The major limitation in the formation of Los is theThe major limitation in the formation of Los is the
requirement of high purity lecithinsrequirement of high purity lecithins
 High purity lecithin is expensiveHigh purity lecithin is expensive
 Difficult to obtain in large quantitiesDifficult to obtain in large quantities
 Inclusion of pluronics as cosurfectant makes organogellingInclusion of pluronics as cosurfectant makes organogelling
feasible with lecithin of relatively less purityfeasible with lecithin of relatively less purity

ConclusionsConclusions
 In the last 10 years, there has been an immense growth in research onIn the last 10 years, there has been an immense growth in research on
organogels and on publications related to organogels. However, only aorganogels and on publications related to organogels. However, only a
few organogels have been investigated for drug delivery, mainly due tofew organogels have been investigated for drug delivery, mainly due to
the fact that the components of most organogels are not pharmaceuticallythe fact that the components of most organogels are not pharmaceutically
acceptable. Thus, before the organogels can be studied as a drug carrier,acceptable. Thus, before the organogels can be studied as a drug carrier,
they must be reformulated using pharmaceutically acceptablethey must be reformulated using pharmaceutically acceptable
components.components.
 Of all the organogels studied, MBGs seem to be the most investigated forOf all the organogels studied, MBGs seem to be the most investigated for
their application as a matrix where enzymes can be immobilized fortheir application as a matrix where enzymes can be immobilized for
biocatalysis of reactions. While in drug delivery, the potential of MBGsbiocatalysis of reactions. While in drug delivery, the potential of MBGs
has not been fully explored.has not been fully explored.

 Lecithin gels have received more attention as transdermal drugLecithin gels have received more attention as transdermal drug
delivery vehicles, presumably due to the presence of lecithin: adelivery vehicles, presumably due to the presence of lecithin: a
known skin permeation enhancer. The promise shown byknown skin permeation enhancer. The promise shown by
lecithin gels as a transdermal delivery vehicle has resulted inlecithin gels as a transdermal delivery vehicle has resulted in
its adoption and adaptation into PLO (which is not anits adoption and adaptation into PLO (which is not an
organogel despite the terminology).organogel despite the terminology).
 PLO is currently the vehicle of choice of US compoundingPLO is currently the vehicle of choice of US compounding
pharmacists and veterinarians for the delivery of drugs by thepharmacists and veterinarians for the delivery of drugs by the
topical route, despite the lack of any hard, scientific evidencetopical route, despite the lack of any hard, scientific evidence
of PLO efficacy as a transdermal drug carrier.of PLO efficacy as a transdermal drug carrier.
 Apart from the topical/transdermal route, organogels haveApart from the topical/transdermal route, organogels have
been also investigated for oral, rectal and parenteralbeen also investigated for oral, rectal and parenteral
applications.applications.

 Sorbitan monostearate organogels have shown promise as parenteralSorbitan monostearate organogels have shown promise as parenteral
vaccine adjuvants and as oral vehicles for poorly water-soluble drugs,vaccine adjuvants and as oral vehicles for poorly water-soluble drugs,
respectively. Given that many drugs suffer from poor water solubility,respectively. Given that many drugs suffer from poor water solubility,
which often leads to low bioavailability, the ability of sorbitanwhich often leads to low bioavailability, the ability of sorbitan
monostearate to solubilise such drugs to increase bioavailability shouldmonostearate to solubilise such drugs to increase bioavailability should
be investigated further.be investigated further.
 Eudragit organogels are different from ‘classical’ organogels in theirEudragit organogels are different from ‘classical’ organogels in their
large, polymeric ‘gelator’, the need for a high gelator concentration,large, polymeric ‘gelator’, the need for a high gelator concentration,
were studied > 10 years ago for rectal delivery. Bioavailability of thewere studied > 10 years ago for rectal delivery. Bioavailability of the
drug from these gels was not higher than from the control formulationdrug from these gels was not higher than from the control formulation
(Witepsol), and it seems that research into Eudragit organogels for(Witepsol), and it seems that research into Eudragit organogels for
rectal delivery has been superseded by research into other, morerectal delivery has been superseded by research into other, more
promising formulations.promising formulations.

 The alanine derivative gels, in situ forming implants (organogels that form in situ,The alanine derivative gels, in situ forming implants (organogels that form in situ,
following the injection of a sol phase) are advantageous over conventional implants infollowing the injection of a sol phase) are advantageous over conventional implants in
that they do not require surgical incision but can be administered by injection, will bethat they do not require surgical incision but can be administered by injection, will be
interesting as sustained-release depot preparations.interesting as sustained-release depot preparations.
 An investigation comparing the different organogels would be of interest to researchersAn investigation comparing the different organogels would be of interest to researchers
and companies seeking to develop a drug-in-organogel formulation. The few organogelsand companies seeking to develop a drug-in-organogel formulation. The few organogels
that have been investigated for drug delivery have yielded interesting results, and it isthat have been investigated for drug delivery have yielded interesting results, and it is
hoped that some of these will make it to the market and improve drug therapy for thehoped that some of these will make it to the market and improve drug therapy for the
benefit of patientsbenefit of patients

ReferencesReferences
 Murdan S. Organogels in drug delivery, Expert Opinion Drug Delivery, 2(3), 2005, 489-Murdan S. Organogels in drug delivery, Expert Opinion Drug Delivery, 2(3), 2005, 489-
505.505.
 Anda Vintiloiu, Jean-Christophe Leroux, Organogels and Their Use in Drug Delivery -Anda Vintiloiu, Jean-Christophe Leroux, Organogels and Their Use in Drug Delivery -
A Review, Journal of Controlled Release, Accepted 27 September 2007, 18-59.A Review, Journal of Controlled Release, Accepted 27 September 2007, 18-59.
 Kumar R and Katare OP. Lecithin organogels as a potential phospholipid-structuredKumar R and Katare OP. Lecithin organogels as a potential phospholipid-structured
system for topical drug delivery: a review, AAPS PharmaSciTech, 6(2), 2005, 298-310.system for topical drug delivery: a review, AAPS PharmaSciTech, 6(2), 2005, 298-310.
 Murdan S. A review of pluronic lecithin organogel as a topical and transdermal drugMurdan S. A review of pluronic lecithin organogel as a topical and transdermal drug
delivery system, Hospital Pharmacist, 12, 2005, 267-270.delivery system, Hospital Pharmacist, 12, 2005, 267-270.
 Shchipunov YA. Lecithin organogel: a micellar system with unique properties, ColloidsShchipunov YA. Lecithin organogel: a micellar system with unique properties, Colloids
and Surfaces: A Physicochemical and Engineering Aspects, 183-185, 2001, 541-554.and Surfaces: A Physicochemical and Engineering Aspects, 183-185, 2001, 541-554.

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