FORMULATION, DEVELOPMENT AND EVALUATION OF SELF

www.wjpps.com Vol 8, Issue 11, 2019.

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Prerna et al. World Journal of Pharmacy and Pharmaceutical Sciences

FORMULATION, DEVELOPMENT AND EVALUATION OF SELF-

MICROEMULSIFYING DRUG DELIVERY SYSTEM OF ACYCLOVIR

Priyanka Kashyap, Navneet Kaur, Dr. Prerna Sarup*

Department of Pharmaceutics Swami Vivekanand College of Pharmacy, Banur.

ABSTRACT

The aim of present work is to developed, formulate and evaluation of

self-micro emulsifying drug delivery system of acyclovir. Acyclovir is

a potent anti-viral agent useful in the treatment of Herpes Simplex

Virus (HSV) infections. Acyclovir exerts its antiviral activity by

competitive inhibition of viral DNA through selective binding of

acyclovir to HSV-thymidine kinase. The main purpose of this work

was to develop self-micro-emulsifying drug delivery system

(SMEDDS) for oral bioavailability and solubility enhancement of

acyclovir. Solubility of acyclovir was determined in various vehicles.

SMEDDS is mixture of oils, surfactants, and co-surfactants, which are

emulsified in aqueous media under conditions of gentle agitation and digestive motility that

would be encountered in the gastro-intestinal (GI) tract. Pseudoternary phase diagrams were

constructed to identify the efficient self-emulsifying region dilution study was also performed

for optimization of formulation. SMEDDS was evaluated for its percentage transmittance,

phase separation study, droplet size analysis, zeta potential, electrophoretic mobility, and

viscosity. The smedds were prepared by using castor oil, tween 80, PEG 200. The optimized

formulation shows maximum% Transparency-93.33% and maximum % Drug content -

91.20%. The emulsion drop generated by TEM were spherical having average size 88.01 nm.

The Average Droplet size of the Optimized SMEDDS formulation B-1 was found to be

88.01. The –ve (-14.3) value of zeta potential indicates that SMEDDS formulation have a net

negative charge. The in vitro release shows 94% release of SMEEDS in 25 minutes.

KEYWORDS: Acyclovir, Castor oil, Tween 80, PEG 200, TEM.

WORLD JOURNAL OF PHARMACY AND PHARMACEUTICAL SCIENCES

SJIF Impact Factor 7.632

Volume 8, Issue 11, 957-977 Research Article ISSN 2278 – 4357

Article Received on

25 August 2019,

Revised on 15 Sept. 2019,

Accepted on 05 Oct. 2019,

DOI: 10.20959/wjpps201911-14932

*Corresponding Author

Dr. Prerna Sarup

Department of

Pharmaceutics Swami

Vivekanand College of

Pharmacy, Banur.


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INTRODUCTION

Solubility

Solubility is defined in quantitative terms as the concentration of solute in a satutated solution

at a certain temperature and in qualitative terms, it may be defined as the spontaneous

interaction of two or more substance to form a homogenous molecular dispersion. A saturated

solution is one in which the solute is in equillibirium with the solvent. The solubility of a

drug may be expressed as parts, percentage, molarity, molality, volume fraction and mole

fraction. Drug solubility is the maximum concentration of the drug solute dissolved in a

solvent under specific condition of temperature, pressure and ph. The drug solubility in a

saturated solution is a static property where as dissolution is a dynamic property that relates

more closely to the bioavalibility rate.[1,2]

Biopharmaceutical Classification System (BCS)

The Biopharmaceutical classification system (BCS) is a drug development tool that allows

estimation of the contributions of three major factors, dissolution, solubility and intestinal

permeability, that effect oral absorption from immediate release (IR) solid oral products.[3]

The fundamental basis of Biopharmaceutical classification system (BCS) was established by

Dr. Gordon Amidon to classify the drug substances with respect to their aqueous solubility

and membrane permeability. Drug substances for which solubility enhancement can improve

the oral bioavailability, are classified in class 2 (poor soluble/high permeable) and class 4

(poor soluble/poor permeable). Especially for class 2 substances, solubility enhancementis a

part of strategies to improve the oral bioavailability.

Figure 1: A typical re presentation of the Biopharmaceutical classification.


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To generally describe “solubility” the pharmacopoeia (USP) uses seven different solubility

expressions as shown in table 1.

Table 1: Solubility definition in USP.

Description

forms(solubility

definition)

Parts of solvent required

for one part of solute

Solubility range

(mg/ml)

Solubility

assigned (mg/ml)

Very soluble <1 >1000 1000

Freely soluble From1 to 10 100-1000 100

Soluble From 10 to 30 33-1000 33

Sparingly Soluble From 30 to 100 10-33 10

Slightly soluble From 100 to 1000 1-10 1

Very slightly soluble From 1000 to 10,000 0.1-1 .01

Recently, due to good and reliable result, there is a great emphasis on self-micro-emulsifying

drug delivery systems (SMEDDS) to improve the oral bioavailability of lipophilic drugs.

Self‐emulsification is a phenomenon which has been exploited commercially for many years

in formulations of emulsifiable concentrates of herbicides and pesticides. The most popular

approach is the incorporation of the active lipophilic compo nent into inert lipid vehicles,

surfactant dispersions self‐emulsifying formulations, emulsions and liposome having

advantage and limitations. SMEDDS or self-emulsifying oil formulations (SEOF) are defined

as isotropic mixtures of natural or synthetic oils, solid or liquid surfactants or, alternatively,

one or more hydrophilic solvents and co‐ solvents/surfactants. There has been growing

interest in the use of lipidic excipients in formulations and, in selfmicro-emulsifying lipid

formulations (SMEDDS) because of their ability to solubilize poorly water‐soluble'

lipophilic' drugs and overcome the problem of poor drug absorption and bioavailability.[4,5]

Potential advantages of SMEDDS systems include[6]

:

1. Enhanced oral bioavailability enabling reduction in dose.

2. More consistent temporal profiles of drug absorption.

3. Selective targeting of drug (s) toward specific absorption window in GIT.

4. Protection of drug (s) from the hostile environment of gut.

5. Control of delivery profiles.

6. Reduced variability including food effects.

7. Protection of sensitive drug substances.

8. High drug payloads.

9. Liquid or solid dosage forms.


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Composition of SMEDDS

The self-micro-emulsifying process depends on

The nature of the oil–surfactant pair

The surfactant concentration

The temperature at which self‐emulsification occurs.

A. Oils

Oils can solubilize the lipophilic drug in a specific amount. It is the most important excipient

because it can facilitate self-emulsification and increase the fraction of lipophilic drug

transported via the intestinal lymphatic system, thereby increasing absorption from the GI

tract. Long‐chain triglyceride and medium‐chain triglyceride oils with different degrees of

saturation have been used in the des ign of SMEDDS. Modified or hydrolyzed vegetable oils

have contributed widely to the success of SMEDDS owing to their formulation and

physiological advantages. Novel semi synthetic medium‐ chain triglyceride oils have

surfactant properties and are widely rep lacing the regular medium‐ chain triglyceride.

B. Surfactant

Nonionic surfactants with high hydrophilic – lipophilic balance (HLB) values are used in

formulation of SM EDDS (e.g., Tween, Labrasol, Labrafac CM 10, Cremophore etc.). The

usual surfactant stre ngth ranges between 30–60% w/w of the formulation in order to form a

stable SMEDDS. S urfactants have a high HLB and hydrophilicity, which assists the

immediate formation of o/w droplets and/or rapid spreading of the formulation in the aqueous

media. S urfactants are amphiphilic in nature and they can dissolve or solubilize relatively

high amounts of hydrophobic drug compounds. This can prevent precipitation of the drug

within the GI lumen and for prolonged existence of drug molecules.

C. Cosurfactant/Cosolvents

Co‐surfactant/Co‐solvents like Spans, capyrol 90, Capmul, lauroglycol, diethylene glycol

monoethyl ether (transcutol), propylene glycol, polyethylene glycol, polyoxyethylene,

propylene carbonate, tetrahydrofurfuryl alcohol polyethylene glycol ether (Glycofurol), etc.,

may help to dissolve large amounts of hydrophilic surfactants or the hydrophobic drug in the

lipid base. These solvents sometimes play the role of the cosurfactants in the microemulsion

systems.


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Table 2: Examples of Oils, Surfactants, Co-surfactant.

Oils Surfactants Co-surfactants/Co –solvent

Cotton seed oil Polysorbate 20 (Tween 20) Polypropylene glycol Soyabean oil Polysorbate 80 (Tween 80) Polyethylene glycol

Corn oil Labrasol Capmul Sunflower oil Cremophor RH40 Ethanol

Castor oil Span 20 Plurol O leique

Ethyl oleate Span 80 Transcutol

MATERIALS AND METHODS

Materials

Active pharmaceutical ingredient (API) (NOSCH Labs Hyderabad), castor oil (Thomas

Baker), Tween 80 (Central Drug House Delhi), PEG 200 (Thomas Baker), Disodium

hydrogen phosphate and Potassium di-hydrogen phosphate (Thomas Baker),, Acetone,

Dimethyl Sulphoxide, Hydrochloric acid and Isopropyl alcohol (Qualigens, Mumbai).

Determination of solubility in various solvents (oils, surfactants and co surfactants)

To find out the appropriate oils, surfactants and co-surfactants as a composition of SMEDDS

the solubility of acyclovir in various oils (castor oil, castor oil, egg oil, oleic acid, paraffin

oil), surfactants (span 80, tween 80, cremophor RH 40, poloxomer-188) and co – surfactants

(propylene glycol, glycerol, ethanol, polyethylene glycol) was determined by using shake

flask method. Briefly, an excess amount of acyclovir (50 mg) was added to each vial

containing 5 mL of the selected vehicle, i.e., oil, co - surfactant and surfactant. After sealing,

the mixture was vortexed for 10min and sonicated by using bath sonicator for 8 mins in order

to facilitate proper mixing of acyclovir with the vehicles and reduce the particle size of the

drug. Mixtures were shaken for 72hrs in an isothermal shaker (Remi, Mumbai, India),

maintained at 37± 1°C, and afterwards, mixtures were centrifuged at 12000 rpm for 10 min

and then supernatant was filtered through membrane filter (0.45μ m) to remove the remaining

insoluble acyclovir. After the appropriate dilution with Dimethyl Sulphoxide the

concentration of acyclovir in the filtrate was determined at 302nm by UV Spectrophotometer

and solubility of acyclovir in different oils, surfactants and co surfactant was calculated with

the help of standard calibration curve.[7,8,9]

Selection of oil, surfactant and co-surfactant

On the basis of solubility studies and compatibility studies oil (castor oil), surfactant (Tween

80) and co-surfactant (PEG) were selected for SMEDDS formulation because of absence of

any type of incompatibility.


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Determination of %transparency between different components (oils, surfactants and

co-surfactants)

On the basis of solubility studies the oils, surfactants and co-surfactants (that have maximum

solubility) were selected and % transparency was determined to find out the maximum

transparency between oil, surfactant and co-surfactant because SMEDDS is a clear

transparent system when diluted with distilled water.[10]

Structural Compatibility studies between drug and polymers

On the basis of %transparency the oil (castor oil), surfactant (tween 80) and co-surfactant

(PEG) were selected because of maximum transparency (property of microemulsion) between

them. Drug polymers compatibility was studied using ATR-FTIR (Bruker

spectrophotometer), and the spectra were recorded in the wavelength region of 4000-450

cm−1. Samples of pure drug, pure polymer, and the physical mixtures containing both the

drug and polymer were scanned in the mentioned wavelength region.

Construction of pseudo- ternary phase diagram

On the basis of the solubility and compatibility testing pseudo-ternary phase diagrams were

constructed by using water titration method to obtain the o/w micro-emulsion region, within

which the concentration range of the components (oil, surfactant and co-surfactant) was

identified. The weight ratio of surfactant (tween 80) to cosurfactant (Km) was varied as 1:1

and 2:1 and the ratio of oil : surfactant/co surfactant was varied as 1:9, 2:8, 3:7, 4:6, 5:5, 6:4,

7:3, 8:2, 9:1. The oil, surfactant and co-surfactant wre mixed in a glass vial and water was

added drop by drop to each oily mixture under proper magnetic stirring at 37 o C until the

mixture became clear and transparent at a certain point. Then the concentrations of the

components were recorded in order to complete the pseudo-ternary phase diagrams, and then

the contents of oil, surfactant, co-surfactant and water at appropriate weight ratios were

selected based on these results.[10,11,12]

Preparation of SMEDDS formulation

With the help of pseudo- ternary phase diagram existing micro emulsion region was found

and concentration of oil, surfactant and co-surfactant at appropriate weight ratios were

selected for SMEDDS formulation (at which clear and transparent micro emulsion was

obtained). A series of SMEDDS formulation (A-1, B-1, B-2) were prepared using castor oil

as oily phase and Tween 80 and polyethylene glycol were used as surfactant and co-

surfactant. Accurately weighed acyclovir was placed in a glass vial and oil, surfactant and co-


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surfactant were added. after adding all the components the mixture was sonicated for 3

minutes using bath sonicator and then glsss vial (containing mixture) kept 30-40 0C for I

minute then all the mixture in a glass vial were vortexed for using vortex shaker until

acyclovir was perfectly dissolved. Then mixture (SMEDDS) was stored at room temperature

for further use.[13]

FORMULATION DEVELOPMENT (Optimization)

Strategy-І

Determination of % transparency of SMEDDS formulation

Three formulations (of different ratio) were selected on the basis of water titration method

(ternary phase diagram) and a transparency study was done to find out the maximum

transparency between oil, surfactant and co-surfactant because SMEDDS is a clear

transparent system when diluted with distilled water.

FORMULATION DEVELOPMENT (Optimization)

Strategy-ІІ

Determination of %Drug Entrapment in SMEDDS

Accurately weighed acyclovir (100mg) was taken in a glass vial and then oil (castor oil),

surfactant (Tween 80) and co-surfactant (PEG) were added in the glass vial. Then the glass

vial was sonicated for 3 minutes and then mixture (SMEDDS) was shaken for 72 hrs at 370 C

using an isothermal shaker (Remi, Mumbai, India). Then the mixture (SMEDDS) was

centrifuged at 12000 rpm for 10 minutes and 1 ml of supernatant was taken and diluted with

Dimethyl Sulphoxide (if necessary) and absorbance was measured at 302 nm by UV

Spectrophotometer .then concentration of acyclovir was determined using standard curve

equation and %drug entrapment was calculated using formula:

% Drug entrapment = practical value/ actual value *100

Preparation of optimized SMEDDS formulation

The final SMEDDS formulation were optimized on the basis of maximum transparency (have

maximum transparency between oil surfactant and co surfactant when diluted with water) and

maximum %drug entrapment present in SMEDDS formulation and then final optimized (A-

1) formulation was prepared.


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Evaluation of Optimized formulation (Acyclovir loaded SMEDDS)

Transmission Electron Microscopy

Because of production of important information on particle size, shape and structure, TEM is

the invaluable tool for material scientists. Only freshly prepared SMEDDS containing

acyclovir was examined for TEM images, because this one shows most expected results

among the other formulations.

Measurement of micro-emulsion Droplet size

Droplet size of the formulation is measured by using the Malvern Zetasizer Nano (1000 HS,

Malvern Instruments, U. K.).

The Zetasizer system determines the size by first measuring the Brownian motion of the

particles in a sample using Dynamic Light Scattering (D L S).

Sample preparation for measurement of droplet size

1 ml of SMEDDS was diluted with 200ml of distilled water in beaker with constant stirring

on a magnetic stirrer. Droplet size of the resulting micro emulsion was determined using the

Zetasizer. (Ma lvern Instruments).

Sample preparation for measurement of Zeta potential

1 ml of SMEDDS was diluted with 200ml of distilled water in beaker with constant stirring

on a magnetic stirrer. Zeta-potential of the resulting micro emulsion was determined using the

Zetasizer. (Ma lvern Instruments).

Viscosity Determination

SMEDDS formulation quantity more than 300ml was taken in beaker. Viscosity of the initial

SMEDDS was measured using Brookfield viscometer.

The needle (spindle) was introduced in the specimen sideways to avo id trapped bubbles at

the bottom, when inside, center it in such a way that the wave produced by it be the same at

all points around the spindle. Turn the viscometer on and let it work freely for a minimum of

30 seconds to a maximum of one minute, in the case the dial was went beyond 100, turn the

viscometer off, place the another suitable spindle number. When this time was over, press the

lever to stop the dial and write down the reading of it Digital viscometer: Viscosity at 25°C =

Direct reading.


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Self-Emulsification studies

SMEDDS formulation were analysed for self-emulsifying property on the basis of clarity

(clear transparent liquid). 1 ml of SMEDDS formulation was added (dropwisely) into 100,

250 and 1000 ml of distilled water, 0.1 N HCL and phosphate buffer of pH 6.8 . This was

done in a glass beaker at room temperature and the contents were gently stirred with a glass

rod. Precipitation was evaluated by visual inspection of the resultant emulsion after 24 hours

(61, 62). The formulation then categorized as stable (clear transparent liquid) or unstable (non

clear turbid liquid or show precipitation).

In Vitro Drug Release Studies

The dissolution study was performed using USP dissolution apparatus II paddle assembly

(DS 8000, LABINDIA, Mumbai, India) at 50 rpm at 37 ± 1°C. The formulations were tested

individually in 0.1 HCl (pH 1.2) and in phosphate buffer (pH 6.8). These media were selected

to mimic the conditions in stomach, small intestine respectively. Aliquot samples were

withdrawn at specified time intervals and were analyzed spectrophotometrically at 275 and

302 nm respectively. The volume of the sample withdrawn each time was replaced with the

same volume of the respective solution.

Accelerated Stability Studies

To assess the drug and formulation stability, stability studies were done according to

International Conference on Harmonization (ICH) and World Health Organization (WHO)

guidelines. The Optimized formulation was stored at 40ºC/75% relative humidity (RH) in

closed glass vials for 6weeks. Beads were analyzed at specified time intervals (0, 1,2,4,6

weeks) for the Physical appearance, %drug content and in vitro dissolution study.

RESULT

Solubility studies

Solubility of acyclovir in different oil, surfactant and cosurfacnt was determined.

Table 3: Solubility of acyclovir in various oils.

S.No OIL Solubility(mg/ml) (mean±SD)

1 Ethyl oleate 5.180±0.001

2 Castor oil 8.426±0.020

3 Paraffin oil 0.412±0.001

4 Egg oil Drug degraded

5 Oleic acid Drug degraded


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Table 4: Solubility of acyclovir in various surfactants.

S.No Surfactant Solubility (mg/ml) (mean±SD)

1 Cremophor RH-40 11.570±0.040

2 Poloxamer- 188 1.606±0.014

3 Tween 80 18.130±0.001

4 Span 80 14.436±0.005

Table 5: Solubility of acyclovir in various co-surfactants.

S.No Co-surfactant Solubility (mg/ml)

(mean±SD)

1 Polyethylene glycol 200 7.317±0.006

2 Propylene glycol 4.051±0.001

3 Ethanol Drug degraded

4 Glycerol Drug degraded

solubility of acyclovir in various oils, surfactants and co-surfactants were determined. On the

basis of solubility oil (castor oil, ethyl oleate) surfactant(Cremophor RH-40, Tween 80) and

co-surfactant (PEG 200 and propylene glycol (in which acyclovir have maximum solubility)

were selected. And a transparency study was done to find out the any compatibility between

oil surfactant and cosurfactant.

Selection of oil, surfactant and co-surfactant

Determination of % transparency between oil, surfactant and co-surfactant:

Table 6: % transparency between Castor oil, Cremophor RH -40, PEG 200.

S.No. component Oil: Smix % transparency (mean±SD)

1 Ethyl oleate

1:1 15.79 ± 0.05 2 Cremophor RH -40

3 PEG 200

Table 7: % transparency between Castor oil, Cremophor RH -40, Polypropylene glycol.

S.No component Oil: Smix %Transparency(mean±SD)

1 Castor Oil

1:1 35.73 ±0.15 2 Cremophor RH -40

3 Polypropylene Glycol

Table 8: % transparency between Ethyl oleate, Tween 80, PEG 200.

S.No component Oil: Smix % transparency(mean±SD)

1 Castor oil

1:1 92.43±0.25 2 Tween 80

3 PEG 200


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Table 9: % transparency between Ethyl oleate, Tween 80, Polypropylene glycol.

S.No Component Oil: Smix % Transparency(mean±SD)

1 Ethyl Oleate

1:1 45.06±0.15 2 Tween 80

3 Polypropylene Glycol

On the basis of %transparency Determined, components of SMEDDS oil (ethyl oleate),

surfactant (tween80) and co-surfactant (PEG) were selected because of maximum

transparency 92.4% (property of microemulsion) between them.

Structural Compatibility studies between drug and polymers

Structural compatibility between and polymers were studied with the help of FTIR spectra of

drug, polymers and FTIR spectra of mixture of drug and polymers.

Figure 2: FTIR spectra of Acyclovir.

Figure 3: FTIR spectra of Drug + polymers.


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all the groups of drug in mixture were present at same value or near it hence no structural

incompatibility was found.

PSEUDO-TERNARY PHASE DIAGRAM: pseudo-ternary phase diagrams were

constructed by using water titration method to obtain the o/w micro-emulsion region, within

which the concentration range of the components (oil, surfactant and co-surfactant) was

identified. The weight ratio of surfactant (tween 80) to cosurfactant (Km) was varied as 1:1

and 2:1 and the ratio of oil : surfactant/co surfactant was varied as 1:9, 2:8, 3:7, 4:6, 5:5, 6:4,

7:3, 8:2, 9:1. TWEEN 80: PEG 200::1.

Fig 4: Ternary phase diagram (km=1:1).

Figure 5.8 is a ternary phase diagram constructed when surfactant : cosurfactant (km) is 1:1.

It reprasents a three components system (oil, water and Cos (surfactant +co surfactant).. The

* (ME) point represents micro emulsion (transparent and clear) reason and other points are of

coarse emulsion (turbid).The * (ME) point depands upon appearance of the sample after

titration with water (0.05 ml water was added at a time).


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Physical Apperance of various SMEDDS formulation (when km=1:1) after water

titration.

S.no. Oil:S/Cos Formulation Code Apperance Observation

1 1:9 A-1 Clear Transparent Microemulsion

2 2:8 A-2 Turbid Coarse emulsion








TWEEN 80: PEG 200:: 2: 1

Figure 5 Ternary phase diagram (km=2:1).

Figure 5.9 is a ternary phase diagram constructed when surfactant : co surfactant (km) is 2:1.

It represents a three components system (Oil, water and Cos (surfactant +co surfactant). The*

(ME) point represents micro emulsion (transparent and clear) reason and other points are of

coarse emulsion (turbid). The* (ME) point depends upon appearance of the sample after

titration with water (0.05 ml water was added at a time).


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Table 5.14: Physical Appearance of various SMEDDS formulation (when km=2:1) after

water titration.

S.No. Oil:S/Cos Formulation Code Apperance Observation

1 1:9 B-1 Clear Transparent Micro emulsion

2 2:8 B-2 Clear Transparent Micro emulsion

3 3:7 B-3 Turbid Coarse emulsion







FORMULATION DEVELOPMENT STRATEGY-І

Table 5.15: Determination of % Transparency of SMEDDS Formulation.

S.No. F.C Oil:S/Cos Km Apperance %Transparency

(mean ± SD)

1 A-1 1:9 1:1 Clear Transparent 78.33±0.35

2 B-1 1:9 2:1 Clear Transparent 95.38±0.40


Figure: 6 % Transparency in formulation A-1, B-1, B-2.

FORMULATION DEVELOPMENT STRATEGY-ІІ

Table 5.16: % Drug entrapment in SMEDDS formulations.

S.No. F.C Oil:S/Cos Km Apperance %Drug entrapment (mean ± SD)

1 A-1 1:9 1:1 Clear Transparent 58.43±0.47




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Figure: 7 Drug entrapment in formulation A-1, B-1, B-2.

Preparation of Optimized SMEDDS Formulation: B-І formulation was optimized because of

maximum% Transparency-93.33% and maximum % Drug content -91.20% and prepared

successfully.

Table 5.17: % Transparency and % Drug content of Optimized SMEDDS Formulation

(B-1).

S.NSS.NO F.C OIL:S/Cos KM %Transparency

(mean ± SD)

%Drug entrapment (mean ±

SD)

1 B-1 1:9 2:1 95.38±0.40 90.20±0.34

Evaluation of optimized SMEDDS formulation

Determination of solubility of Acyclovir in SMEEDS

The solubility of acyclovir in SMEDDS formulation was determined using shaking flask

method. Solubility of acyclovir in SMEDDS formulation was found to be 16.84 mg/ml.

Solubility of acyclovir in Aqueous solution was 0.3 mg/ml but in SMEDDS formulation this

was found that 19.44mg/ml hence solubility increases 64.8% via SMEDDS formulation.

Morphology (TEM).


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Fig 8: TEM Image of Microemulsion Droplets.

TEM study indicated that microemulsion generated from optimized formulation, appeared as

black spots on a white background. The emulsion drop generated were spherical having

average size 88.01 nm.

Measurement of microemulsion droplet size

Droplet size of the Optimized SMEDDS formulation B-1 (1 ML was diluted with 200 ml of

Distilled water) was measured by using the Malvern Zetasizer Nano 1000 HS.

The Average Droplet size of the Optimized SMEDDS formulation B-1 was found to be 88.01

and PDI value is 0.405.

The average size 82.01 nm indicates that micro emulsion generated and PDI value 0.405

indicates that uniform micro emulsion was formed.

Figure 9: Droplet size distribution graph.


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Measurement zeta potential

The droplets of Micro-emulsion having -ve charge and no aggregation of globule was

formed. Zeta- potential of the resulting Micro- emulsion was determined using the Zetasizer.

(Malvern Instruments).

The –ve (-14.3) value of zeta potential indicates that SMEDDS formulation have a net

negative charge. Due to –ve charge on micro emulsion droplets there is a repulsive force

between droplets due to which there is no aggregation of micro emulsion droplet and hence

better micro emulsion will formed.

Figure 10: Zeta potential of SMEDDS formulation.

Viscosity Determination

Viscosity of SMEDDS was measured by using the Brookfield Viscometer and spindle no.2

was used for the particular study.

Table 5.18: Viscosity of the SMEDDS formulation.

Formulation viscosity rpm Torque

SMEDDS 745 cP 30 13

Self-Emulsification studies

SMEDDS formulations were analyzed for self-emulsifying property on the basis of clarity

(clear transparent liquid). 1 ml of SMEDDS formulation was added (drop wisely) into 100,

250 and 1000 ml of distilled water, 0.1 N HCL and phosphate buffer of pH 6.8. The

formulation then after 24 hours categorized as stable (Clear transparent liquid) or unstable

(turbid liquid or show precipitation).


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Table 11: Dilution of SMEDDS with different media.

S.no. Formulation Vehicle Qty. Observation

1 SMEDDS Distilled water 100 ml Clear, No Precipitation

2 SMEDDS 0.1 N HCL 100 ml Clear, No Precipitation

3 SMEDDS Phosphate buffer (6.8 pH) 100 ml Clear, No Precipitation







In-Vitro Dissolution studies

The dissolution study was performed using USP dissolution apparatus II paddle assembly

(DS 8000, LABINDIA, Mumbai, India) in 900 ml of 0.1 N HCL at 100 rpm at 37 ± 1°C.

In-Vitro dissolution In 0.1 N HCL

Table 5.20: % CDR of SMEDDS formulation and Plain drug in 0.1 N HCL.

S.No Time (min.) % CDR (Formulation) (mean±SD) %CDR

(Plain) (mean±SD)

1 0 0 ± 0.00 0 ± 0.00

2 5 20.70 ± 1.01 8.57 ± 0.66

3 10 31.85 ± 1.33 9.49 ± 0.38

4 15 51.32 ± 1.65 10.21 ± 0.38

5 20 70.14 ± 1.67 10.93 ± 0.37

6 25 94.02 ± 0.99 11.65 ± 0.37

7 30 - 12.37 ± 1.01

8 35 - 13.33 ± 1.01

9 40 - 14.50 ± 0.77

10 45 - 15.90 ± 0.78

11 50 - 17.09 ± 0.68

12 55 - 18.29 ± 0.40

13 60 - 19.71 ± 0.77


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Figure 5.17 Comparative results of % CDR from SMEDS formulation and plain drug in

0.1 N HCL.

Accelerated Stability Studies

The Optimized formulation was stored at 40ºC/75% relative humidity (RH) in closed glass

vials for 6weeks. SMEDDS were analyzed at specified time intervals (0, 2, 4, 6 weeks) for

the % transparency, %drug content and in vitro dissolution study.

Table 5.22: %TRANSPARENCY, % DRUG entrapment in optimized formulation at

different time interval (0, 2, 4, 6 weeks)

S.No. Time (in weeks) % Transparency % Drug Content

1 0 93.33 91.20

2 2 92.75 90.60

3 4 91.86 90.35

4 6 91.58 90.33

In- Vitro Dissolution

Table 5.23: Dissolution profile In 0.1 N HCL at different time interval (0, 2, 4, 6 weeks).

S.No Time (min.) %CDR (weeks)

0 2 4 6

1 0 0 ± 0.00 0 ± 0.00 0 ± 0.00 0 ± 0.00

2 5 20.70 ± 1.01 20.92± 0.76 20.26 ± 0.38 18.05 ± 0.76

3 10 31.85 ± 1.33 31.18 ± 1.32 27.87 ± 1.75 26.31 ± 0.37

4 15 52.32 ± 1.65 52.09 ±1.00 49.87 ± 0.01 49.85 ± 0.66

5 20 71.14 ± 1.67 69.59 ± 0.76 68.46 ± 1.66 66.89 ± 0.37

6 25 96.02 ± 0.99 95.13 ± 0.77 93.32 ± 0.76 93.25 ± 0.66


976


Figure 5.19 % CDR of Acyclovir from SMEDDS formulation at different time interval

(0, 2, 4, 6 weeks) in 0.1 N HCL (pH 1.2).

CONCLUSION

Acyclovir, an antiviral drug is a poorly water soluble drug with a pKa, 2.27 having a pH

dependent solubility and dissolution rate. Acyclovir showed a good absorption from

gastrointestinal tract but due to poor solubility or dissolution rate in gastrointestinal tract it

shows low and erratic bioavailability (absorption rate) and hence absorption was delayed to a

varying extent after oral administration. Being a poorly water soluble drug, there exist a lag

time between dosage administration and eliction of pharmacological response.

In order to get a better dissolution rate the solubility of acyclovir is enhanced by self-micro

emulsifying drug delivery system and an immediate release formulation was developed to get

quick pharmacological response.

From in vitro dissolution study it was proved that SMEDDS formulation releases drug at

faster rate, thus the objective of increase solubility and hence the better dissolution rate for

uniform bioavailability via SMEDDS formulation of acyclovir was successfully achieved.

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