DEPARTMENT OF PHARMACEUTICS
R. C. Patel Institute of Pharmaceutical Education & Research;
Dist: Dhule, Maharashtra.
Savale Sagar Kishor
M. Pharm (1st sem)
Date - 3/10/2015
3. Types of SMDDS
4. Aim of SMDDS
5. Advantages of SMDDS
6. Disadvantages of SMDDS
7. Composition of SMDDS
8. Mechanism of SMEDDS
9. Formulation of SMEDDS
10. Evalution of SMEDDS
11. Applications of SMEDDS
1. In recent years, much attention has been focused on oral dosage forms using a self-micro emulsifying
drug delivery system (SMEDDS) for the purpose of improving the solubility and absorption of poorly
2. SMEDDS consists of a mixture of drugs, oils, surfactants and/or other additives.
Gentle mixing of these ingredients in aqueous media generates micro-emulsions with a droplet size in a
range of 10-100 nm.
3. SMEDDS has been shown to improve absorption of drugs by rapid self-micro
emulsification in the stomach, with the micro-emulsion droplets subsequently dispersing in the
gastrointestinal tract to reach sites of absorption .
4. resultant small droplet size from SMEDDS provides a large interfacial surface area for drug release and
absorption, and the specific components of SMEDDS promote the intestinal lymphatic transport of drugs
Oral absorption of several drugs has been enhanced by SMEDDS.
Definition- “SMEDDS are defined as isotropic mixtures of natural or synthetic oils, solid
and liquid surfactants”.
alternatively, one or more hydrophilic solvents and co-solvents/surfactants that have a
unique ability of forming fine oil-in-water (o/w) micro emulsions upon mild agitation
followed by dilution in aqueous media, such as GI fluids.
Self Micro-Emulsifying Drug Delivery System (SMEDDS)
The basic difference between self emulsifying drug delivery systems (SEDDS) also called as
self emulsifying oil formulation (SEOF)
SMEDDS is SEDDS typically produce opaque emulsions with a droplet size between 100
and 300 nm
SMEDDS form transparent micro emulsions with a droplet size of less than 50 nm
the concentration of oil in SMEDDS is less than 20 % as compared to 40-80% in SEDDS.
Most of the new drug candidates in development today are
sparingly soluble and associated with poor bioavailability
The main purpose is to prepare SMEDDS for “oral
bioavailability enhancement of a poorly water soluble
AIM OF SMEDDS
according to bio pharmaceutical
the class II drugs have poor solubility and
high permeability , thus the rate limiting
process of absorption is the drug
dissolution step. Formulation plays the
major role in improving the rate and extent
of absorption of such drugs from GI tract.
Advantages of SMEDDS
1. Improvement in oral bioavailability
Dissolution rate dependent absorption is a major factor that limits the bioavailability of numerous poorly
water soluble drugs. The ability of SMEDDS to present the drug to GIT in solubilized and micro emulsified
form (globule size between 1-100 nm) and subsequent increase in specific surface area enable more
efficient drug transport through the intestinal aqueous boundary layer and through the absorptive brush
border membrane leading to improved bioavailability
2.Ease of manufacture and scale-up
Ease of manufacture and scale- up is one of the most important advantages that make SMEDDS unique
when compared to other drug delivery systems like solid dispersions, liposomes, nano particles, etc.,
dealing with improvement of bio-availability. SMEDDS require very simple and economical manufacturing
facilities like simple mixer with agitator and volumetric liquid filling equipment for large-scale
manufacturing. This explains the interest of industry in the SMEDDS.
3. Reduction in inter-subject and intra-subject variability and food effects
There are several drugs which show large inter-subject and intra-subject variation in absorption leading to
decreased performance of drug and patient non-compliance. Food is a major factor affecting the therapeutic
performance of the drug in the body. SMEDDS are a benefit for such drugs. Several research papers
specifying that, the performance of SMEDDS is independent of food and, SMEDDS offer reproducibility
of plasma profile are available 11
4. Ability to deliver peptides that are prone to enzymatic hydrolysis in GIT
One distinctive property that makes SMEDDS superior as compared to the other drug delivery systems is
their ability to deliver macromolecules like peptides, hormones, enzyme substrates and inhibitors and their
ability to offer protection from enzymatic hydrolysis. The intestinal hydrolysis of pro drug by
cholinesterase can be protected if Polysorbate 20 is emulsifier in micro emulsion formulation .These
systems are formed spontaneously without aid of energy or heating thus suitable for thermo labile drugs
Advantages of SMEDDS over emulsion
1.SMEDDS not only offer the same advantages of emulsions of facilitating the solubility of hydrophobic drugs, but
also overcomes the drawback of the layering of emulsions after sitting for a long time. SMEDDS can be easily stored
since it belongs to a thermodynamics stable system.
2. Microemulsions formed by the SMEDDS exhibit good thermodynamics stability and optical transparency. The
major difference between the above microemulsions and common emulsions lies in the particle size of droplets. The
size of the droplets of common emulsion ranges between 0.2 and 10 μm, and that of the droplets of microemulsion
formed by the SMEDDS generally ranges between 2 and 100 nm (such droplets are called droplets of nano
particles).Since the particle size is small, the total surface area for absorption and dispersion is significantly larger
than that of solid dosage form and it can easily penetrate the gastrointestinal tract and be absorbed. The
bioavailability of the drug is therefore improved.
3. SMEDDS offer numerous delivery options like filled hard gelatin capsules or soft gelatin capsules or
can be formulated in to tablets whereas emulsions can only be given as an oral solutions. 12
Dis-Advantages of SMEDDS
1.One of the obstacles for the development of SMEDDS and other lipid-based formulations is the lack of good predicative
in vitro models for assessment of the formulations.
2. Traditional dissolution methods do not work, because these formulations potentially are dependent on digestion prior to
release of the drug.
3. This in vitro model needs further development and validation before its strength can be evaluated.
4. Further development will be based on in vitro - in vivo correlations and therefore different prototype lipid based
formulations needs to be developed and tested in vivo in a suitable animal model.
4. The drawbacks of this system include chemical instabilities of drugs and high surfactant concentrations in formulations
(approximately 30-60%) which irritate GIT.
6. Moreover, volatile co solvents in the conventional self-micro emulsifying formulations are known to migrate into the
shells of soft or hard gelatin capsules, resulting in the precipitation of the lipophilic drugs.
7. The precipitation tendency of the drug on dilution may be higher due to the dilution effect of the
8. Formulations containing several components become more challenging to validate. 13
COMPOSITION OF SMEDDS
In order to make SMEDDS systems pharmaceutically acceptable, it is necessary to
prepare such systems by using nontoxic and safe components. Oil from natural
sources and their derivatives, e.g. triglycerides and fatty acid methyl esters are easily
degraded by microorganism and considered to be harmless to the environment. The
formation of bicontinuous micro emulsions with mineral
oils has been intensively investigated in model experiments and for application in
industrial products. An acceptable lipophilic phase for pharmaceutical uses
would be vegetable oils. The extension of a microemulsion region generally depends
on nature of oil. This is due to differences in oil penetration into the
Castor oil, Sunflower oil, Olive oil, Seseam oil,
Hydrogenated specialty oils
A surfactant molecule is formed by two parts with different affinities for the solvents.
One of them has affinity for water (polar solvents) and the other has for oil
(non-polar solvents). A little quantity of surfactant molecules rests upon the water-air
interface and decreases the water surface tension value (the force per unit area
needed to make available surface). That is why the surfactant name: “surface active
Surfactant molecules may be classified based on the nature of the hydrophilic group
within the molecule. The four main groups of surfactants are
defined as follows,
1. Anionic surfactants
2. Cationic surfactants
3. Ampholytic surfactants
4. Nonionic surfactants
1. Anionic Surfactants, where the hydrophilic group carries a negative charge such as
carboxyl (RCOO-),sulphonate (RSO3-) or sulphate (ROSO3-).
Examples: Potassium laurate, sodium lauryl sulphate.
2: Cationic surfactants, where the hydrophilic group carries a positive charge.
Example: quaternary ammonium halide.
3: Ampholytic surfactants (also called zwitterionic surfactants) contain both a
negative and a positive charge.
4. Nonionic surfactants, where the hydrophilic group carries no charge but
derives its water solubility from highly polar groups such as hydroxyl or
Examples: Sorbitan esters (Spans), polysorbates (Tweens).
Nonionic surfactants with high hydrophiliclipophilic balance (HLB)
values are used in formulation of SMEDDS. The usual surfactant strength
ranges between 30-60% w/w of the formulation in order to form a stable
SMEDDS.Surfactants having a high HLB and hydrophilicity assist the
immediate formation of o/w droplets and/or rapid spreading of the
formulation in the aqueous media. Surfactants are amphiphilic in nature
and they can dissolve or solubilize relatively high amount of hydrophobic
Organic solvents such as ethanol, propylene glycol (PG) and polyethylene glycol (PEG) are
suitable for oral delivery and they enable the dissolution of large quantities of either the
hydrophilic surfactant or the drug in the lipid base.
solvents can even act as co surfactants in microemulsion systems. Alternately alcohols and
other volatile cosolvents have the disadvantage of evaporating into the shells of the soft
gelatin or hard sealed gelatin capsules in conventional SMEDDS leading to drug
For the production of an optimum SMEDDS, high concentration of surfactant is required
in order to reduce interfacial tension sufficiently, which can be harmful, so co-surfactants
are used to reduce the concentration of surfactants. Co-surfactants together with the
surfactants provide the sufficient flexibility to interfacial film to take up different
curvatures required to form micro-emulsion over a wide range of composition. Selection
of proper surfactant and co-surfactant is necessary for the efficient design of SMEDDS
and for the solubilization of drug in the SMEDDS.
self-emulsification occurs when the entropy change that favors dispersion is greater than
the energy required to increase the surface area of the dispersion.
The free energy of a conventional emulsion formation is a direct function of the energy
required to create a new surface between the two phases and can be described by equation
Where, G is the free energy associated with the process (ignoring the free energy of
mixing), N is the number of droplets of radius, r, and Ợ represents the interfacial energy.
With time, the two phases of the emulsion will tend to separate, in order to reduce the
interfacial area, and subsequently, the free energy of the systems.
Formulation of SMEDDS
Drug has to dissolve in to oil phase(lipophilic part) of microemulsion.
Water phase is combined with the surfactant and then cosurfactant 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.
Ultrasonicator can finally used to achieve the desired range for the
It is then allow to equilibrate.
Gel may be prepared by the addition of the gelling agent to above
For four or more components pseudo ternary phase
diagrams are used to study the phase behaviour.
In this diagram a corner represent a binary mixture
of two components such as water/drug, oil/drug or
A quaternary phase diagram is time consuming .
pseudo ternary phase diagram is constructed to
find out the different zones of micro emulsions.
METHOD OF PREPARATION
1. Phase Titration Method
2. Phase inversion Method
1. Phase Titration Method
dilution of an oil-surfactant mixture with water.(w/o)
dilution of a water-surfactant mixture with oil.(o/w)
mixing all components at once. In some systems, the order of ingredient addition may determine whether a
2.Phase inversion method
Phase Inversion Temperature (PIT), i.e., the temperature range in which an o/w microemulsion inverts to a
w/o type or vice versa.
1. Thermodynamic Stability Studies
2. Dispersibility test
3. Turbidimetric Evaluation
4. Viscosity Determination
5. Droplet Size Analysis and Particle Size Measurements
6. Refractive Index and Percent Transmittance
7. Electro Conductivity Study
8. In vitro Diffusion Study
9. Drug Content
10. In vivo permeability studies
1. THERMODYNAMIC STABILITY STUDIES
Heating cooling cycle
•Six cycles between refrigerator temperature 4⁰C and 45⁰C with storage at each temperature of not less than 48 h is
•Those formulations, which are stable at these temperatures, are subjected to centrifugation test.
•Passed formulations are centrifuged at room temperature at 3500 rpm for 30 min.
•Those formulations that does not show any phase separation are taken for the freeze thaw stress test.
Freeze thaw cycle:-
Freeze was employed to evaluate the stability of formulation.
Thermodynamic stability was evaluated at difference temp. To check the effect of temp. the formulation was
subjected to freeze thaw cycle(-20ºC) for 2-3 days.
Those formulations passed this test showed good stability with no phase separation, creaming, or
The efficiency of self-emulsification of oral nano or micro emulsion is evaluated by using a standard USP
XXII dissolution apparatus for dispersibility test.
Solution Tested: 1ml
Medium: 500 ml water
Temperature: 37 ± 1 ⁰C.
Paddle speed : 50 rpm
Grade A: Rapidly forming (within 1 min) nano-emulsion, having a clear or bluish appearance.
Grade B : Rapidly forming slightly less clear emulsion having a bluish white appearance.
Grade C: Fine milky emulsion that formed within 2 min.
Grade D: Dull, grayish white emulsion having slightly oily appearance that is slow to
emulsify (longer than 2 min).
Grade E: Formulation, exhibiting either poor or minimal emulsification with large oil
globules present on the surface.
Grade A and Grade B formulation will remain as nanoemulsion when dispersed in GIT.
While formulation falling in Grade C could be recommended for SMEDDS formulation.
Nepheloturbidimetric evaluation is done to monitor the growth of emulsification.
Fixed quantity of Self emulsifying system is added to fixed quantity of suitable medium (0.1N
hydrochloric acid) under continuous stirring (50 rpm) on magnetic hot plate at appropriate
temperature, and the increase in turbidity is measured, by using a turbidimeter.
However, since the time required for complete emulsification is too short, it is not possible to monitor
the rate of change of turbidity (rate of emulsification)
The SMEDDS system is generally administered in soft gelatin or hard gelatin capsules. So, it should be easily
pourable into capsules and such systems should not be too thick.
The rheological properties of the micro emulsion are evaluated by Brookfield viscometer.
The viscosities determination conform whether the system is w/o or o/w.
If the system has low viscosity then it is o/w type of the system
If the system has high viscosity then it is w/o type of the system
The droplet size of the emulsions is determined by photon
correlation spectroscopy (which analyses the fluctuations
in light scattering due to Brownian motion of the
particles) using a Zetasizer able to measure sizes between
10 and 5000 nm.
6. REFRACTIVE INDEX AND PERCENT TRANSMITTANCE:-
Refractive index and percent transmittance prove the transparency of formulation.
The refractive index of the system is measured by refractometer by putting a drop of solution on slide
and comparing it with water (1.333).
The percent transmittance of the system is measured at particular wavelength using UV spectrophotometer by using
distilled water as blank.
If refractive index of system is similar to the refractive index of water (1.333) and formulation have percent
transmittance > 99 percent, then formulation have transparent nature. 33
7.ELECTRO CONDUCTIVITY STUDY:-
The SMEDD system contains ionic or non-ionic surfactant, oil, and water.
This test is performed for measurement of the electro conductive nature of system.
The electro conductivity of resultant system is measured by electro conductometer.
In conventional SEDDSs, the charge on an oil droplet is negative due to presence of free
8.INVITRO DIFFUSION STUDY:-
In vitro diffusion studies are carried out to study the drug release behavior of
formulation from liquid crystalline phase around the droplet using dialysis
Drug from pre-weighed SMEDDS is extracted by dissolving in suitable
solvent. Drug content in the solvent extract was analyzed by suitable
analytical method against the standard solvent solution of drug.
SUPERSATURABLE SMEDDS (S-SMEDDS):
The high surfactant level typically present in SMEDDS formulation can lead to GI side effects and a new class of
supersaturable formulations including supersaturable SMEDDS. (S-SMEDDS) formulations have been designed and
developed to reduce the surfactant side effects and achieve rapid absorption of poorly soluble drugs
SOLID SMEDDS: SMEDDS are normally prepared as liquid dosage forms that can be administrated in soft gelatin
capsules, which have some disadvantages especially in the manufacturing process. An alternative method is the
incorporation of liquid self emulsifying ingredients into a powder in order to create a solid dosage form (tablets,
capsules). A pellet formulation of progesterone in SMEDDS has been prepared by the process of extrusion /
spheronization to provide a good in vitro drug release (100% within 30 min, T50% at 13 min). The same dose
of progesterone (16 mg) in pellets and in the SEDDS liquid formulation resulted in similar AUC, C max and
T max values2
Marketed Product of SMEDDS
Drug Name Compound Dosage form
Neoral® Cyclosporine A/I Soft gelatin capsule Novartis Immune suppressant
Norvir® Ritonavir Sof tgelatin capsule
Fortovase® Saquinavir Soft gelatin capsule
Roche inc. HIV antiviral
Agenerase® Amprenavir Soft gelatin capsule Glaxo Smithkline HIV antiviral
Convulex® Valproic acid Soft gelatin capsule Pharmacia Antiepileptic
Lipirex® Fenofibrate Hard gelatin capsule Genus
Sandimmune® Cyclosporine A/II Soft gelatin capsule Novartis Immuno suppressant
Targretin® Bexarotene Soft gelatin capsule Ligand Antineoplastic
Rocaltrol® Calcitriol Soft gelatin capsule Roche Calcium regulator
Gengraf® Cyclosporine A/III Hard gelatin capsule Abbott Laboratories Immuno suppr
Self-microemulsifying drug delivery system is a novel approach for the
formulation of drug compounds with poor aqueous solubility. Self micro
emulsifying drug delivery systems (SMEDDS) are mixtures of oils, Cosolvents
and surfactants, which is isotropic in nature. When introduced into aqueous
phase, it emulsifies spontaneously to produce fine o/w emulsion under
gentle agitation. SMEDDS represent a good alternative for the formulation of
poorly water soluble drugs. SMEDDS improve the dissolution of the drug due
to increased surface area on dispersion and solubility effect of surfactant.
The oral delivery of hydrophobic drugs can be made possible by SMEDDSs,
which have been shown to substantially improve oral bioavailability. By this
approach it is possible to prolong the release of drug via incorporation of
polymer in composition. SMEDDS appears to be unique &industrially feasible
approach. With future development.
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2.Tang J: Self-Emulsifying Drug Delivery Systems: strategy for improving oral delivery of poorly
soluble drugs. Cur Drug Th 2007; 2: 85-93.
3.Burcham DL, Maurin MB, Hausner EA and Huang SM: Improved oral bioavailability of the
hypocholesterolemic DMP 565 in dogs following oral dosing in oil and glycol solutions. Biopharmaceutics &
Drug Disposition 1997; 18:737-742.
4. Serajuddin AT, Sheen PC, Mufson D, Bernstein DF and Augustine MA: Effect of vehicle amphiphilicity on
the dissolution and bioavailability of a poorly water soluble drug from solid dispersion. Journal of
Pharmaceutical Sciences 1988; 77:414-417.
5.Pouton CW: Effects of the inclusion of a model drug on the performance of self-emulsifying formulations.
Journal of Pharmacy & Pharmacology 1985; 37:1p.