A brief description of Micro emulsion . Prepared by a student of pharmacy.

1. SEMINAR ON
MICROEMULSION
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PREPARED BY : PRIYANKA MANOJ GALHOTRA

2. CONTENTS
 Introduction
 Microemulsion as drug carrier
 Disadvantages
 Microemulsion vs Emulsion
 Types of Microemulsion
 Theory of Microemulsion
 Components of Microemulsion formation
 Preparation of Microemulsion
 Factors influencing formation of Microemulsion
 Microemulsion characterisation
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3.  Evaluation parameter studies
 Applications
 Different categories of drugs solubilized
in microemulsion
 Conclusion
 References
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4. INTRODUCTION
 Microemulsions are thermodynamically
stable, optically transparent, isotropic
dispersions of aqueous and hydrocarbon
liquids stabilized by an interfacial film of
surfactants molecules.
 The term microemulsion was first defined
by Schulman and Friend in 1940. Since
that time, microemulsions have found a
wide range of applications, from oil
recovery to synthesis of nanoparticles.
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5. Fig: Microemulsion
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6. MICROEMULSION AS A DRUG
CARRIER SYSTEM
 Improved drug solubilisation
 Long shelf life
 Ease of preparation
 Improved bioavailability
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7. DISADVANTAGES
 Microemulsion stability is influenced by
environmental parameters such as
temperature and pH.
 Limited solubilizing capacity for high
melting substances
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8. TYPES OF MICROEMULSION
 Microemulsions are dynamic systems which the
interface is continuously and spontaneously
fluctuating. Structurally they are divided into oil-in-
water (o/w), water in oil (w/o) and bicontinuous
microemulsion.
 In all types of microemulsions, the interface is
stabilized by an appropriate combination of
surfactants and or co-surfactants.
 The mixture of oil, water and surfactants is able to
form a wide variety of structures and phases
depending upon the proportions of the components.
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9. Fig : Types of Microemulsion
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10. COMPARISON OF MICROEMULSION
AND EMULSION
PROPERTY MICROEMULSION EMULSION
Appearance Transparent Cloudy
Droplet size 20-200 nm >500nm
Interfacial tension Ultra low High
Stability Thermodynamically
stable, long shelf life
Thermodynamically
unstable, will eventually
phase separate out
Optical Isotropy Isotropic Anisotropic
Phases Monophasic Biphasic
Viscosity Low viscosity with
Newtonian behaviour
Higher viscosity
Preparation Facile preparation,
relatively lower cost for
commercial production
Require a large input of
energy , higher cost
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11. THEORY OF MICROEMULSION
 The understanding of basis for
thermodynamic stability of microemulsion
several thermodynamic theories are
proposed.
 In 1975, Ruckenstein and Chi considered the
free energy formation of microemulsion to
be consisted of three contributions:
 Interfacial energy
 Energy of interaction o/w droplets
 Entropy of dispersion
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12.  The free energy of microemulsion formation can
be considered to depend on the extent to which
surfactant lowers the surface tension of oil-water
interface and the change in entropy of the system
such that:
∆G f = ᵞ∆A-T∆S
∆Gf = Free energy formation
ᵞ = Surface tension of oil-water interface
∆A= Change in interfacial area on microemulsion
∆S = Change in entropy of system
T= Temperature
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13. 13
Microemulsion is formed when
The interfacial tension at the o/w inter
phase are brought at very low level.
The interfacial tension is kept at highly
flexible and fluid.

14. COMPONENTS OF MICROEMULSION
FORMULATIONS
 The components are:
 Oil
 Surfactants
 Co-surfactants
 Water
 Selection of materials that are biocompatible,
non-toxic, clinically acceptable and use
emulsifiers in a suitable concentration range
that will result in non-aggressive and mild
microemulsion.
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15. LISTS OF OILS ,SURFACTANTS AND
CO-SURFACTANTS
OIL PHASE SURFACTANT CO-SURFACTANT
Isopropyl Myristate Tween 80 Propylene glycol
Safflower oil Tween 40 Ethylene glycol
Olive oil Span 40 Ethanol
Mineral oil Labrafil M1944CS 1-Butanol
Medium chain
triglyceride
Polyoxyethylene-35-
ricinoleate
Isopropyl alcohol
Soyabean oil Brij 58 PEG 600
Captex355 Cremophorel Glycerol
Sunflower oil Lecithin PEG 400
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16. OIL
 As compare to long chain alkanes, short
chain oil penetrate the tail group region to a
greater extent and resulting in increase
negative curvature (and reduced effective
HLB)
 The main criteria for the selection of oil is
that the drug should have high solubility in
it.
 This will minimise the volume of the
formulation to deliver the therapeutic dose of
the drug in concentration.
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17. SURFACTANTS
 The desirable properties of a surfactants to
form a microemulsion are:
 Increase the viscosity of emulsion
 Be effective in a reasonably low
concentration
 Provide a flexible film that can readily
deform around small droplets.
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18.  It is to lower the interfacial tension which
will ultimately facilitates dispersion
process and provide a flexible around the
droplets.
 Generally low HLB (3-6) surfactants are
suitable for w/o microemulsion.
 For high HLB (8-18) are suitable for o/w
microemulsion.
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19. CO-SURFACTANTS
 The single-chain surfactants alone are
unable to reduce the o/w interfacial
tension sufficiently to enable a
microemulsion to form than it takes in
general cases.
 The presences of co-surfactants allows the
interfacial film sufficiently flexibility to
take up different curvatures required to
form microemulsion over a wide range of
composition.
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20.  Short to medium chain length alcohols
(C3-C8) reduces the interfacial tension
and increases the fluidity of the interface.
 Surfactants having HLB greater than 20
often require the presence of co-surfactant
to reduce their effective HLB to a value
within the range required for
microemulsion formulation
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21. PREPARATION OF MICROEMULSION
 Drug has to dissolve in to oil phase
(lipophilic part) of microemulsion.
 Water phase is combined with the surfactant
and then co-surfactant is added slowly with
constant stirring until the system is become
transparent.
 The amount of surfactant and co-surfactant
to be added and the parent oil phase that can
be incorporated is determined with the help
of pseudo ternary phase diagram.
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22.  Ultrasonicator can finally used to achieve
the desired range for the dispersed phase.
 It is then allow to equilibrate.
 Gel may be prepared by the addition of
the gelling agent to above microemulsion.
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23. METHODS
 Two methods of microemulsions are:
 Phase titration method
 Phase inversion method
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24. Fig: Phase Behaviour
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25. FACTORS INFLUENCING FORMATION
OF MICROEMULSION
 Effect of surfactants
 Effect of Co-surfactant
 Effect of oil type
 Effect of HLB
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26. MICROEMULSION CHARACTERISATION
 Macroscopic Study
 Particle size analysis
 Electron microscopy
 Nuclear Magnetic Resonance Method
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27. MICROEMULSION USED IN
 Microemulsion is used in:
 Self micro-emulsifying drug delivery
system
 Self emulsified drug delivery system
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28. EVALUATION PARAMETERS STUDIES
 Phase behaviour
 Size and shape
 Rheology
 Conductivity
 pH
 Drug release studies
 Physical stability study
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29. APPLICATIONS
 Parenteral Administration
 Oral drug delivery
 Tropical drug delivery
 Ocular pulmonary delivery
 Microemulsion in biotechnology
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30. DIFFERNT CATAGORIES OF DRUGS
SOLUBILIZED IN MICROEMULSION
CATEGORY DRUGS
Anti-neoplastics Doxorubicin
Peptide Drug Cyclosporin
Sympatholytic Timolol
Local Anaesthetics Lidocaine ,Benzocaine
Steroids Hydrocortisone,
Testosterone
Anxiolytics Diazepam
Vitamins Tocopherol, Ascorbic acid
Anti-inflammatory Indomethacin
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31. MARKETED PREPARATION
Brand Drug Dosage
Form
Dose (mg) Indication
Neoral* Cyclosporin Soft gelatin
capsule
25 ,100 Immunosuppres
sant
Norvir* Ritonavir Soft gelatin
capsule
100 HIV antiviral
Lipire* Fenofibrate Hard gelatin
capsule
200 Antihypertensiv
e
Convule* Valproic acid Soft gelatin
capsule
100,200 Antiepileptic
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32. CONCLUSION
 Microemulsions are optically isotropic
and thermodynamically stable liquid
solutions of oil, water and amphiphile.
 Microemulsions are readily distinguished
from normal emulsions by their
transparency, low viscosity and more
fundamentally their thermodynamic
stability.
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33.  Drug delivery through microemulsions is
a promising area for continued research
with the aim of achieving controlled
release with enhanced bioavailability and
for drug targeting to various sites in the
body.
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34. REFERENCES
 Jain N.K., Controlled and novel drug
delivery, CBS publisher, New Delhi, page
no:27-49
 Lachman, Lieberman’s, The theory and
practice of industrial pharmacy, Fourth
edition, CBS publishers and distributors,
page no: 687,894.
 Dr. D. Baviskar., Dr. D. Jain Novel Drug
Delivery Systems, Nirali prakashan, page
no: 19.1-19.14
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35.  R.S.R.Murthy, Vesicular and Particulate
Drug Delivery Systems, Career
Publications , page no: 105-140
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36. THANK YOU
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