mikroemulsi 1

580 ASIAN J. EXP. BIOL. SCI. VOl 1 (3) 2010

Society of Applied Sciences

Design and Evaluation of Micro emulsion Based Drug Delivery System K.R.

Jadhav

, S.L. Shetye

and V.J. Kadam

Department of Pharmaceutics, Bharati Vidyapeeths College of Pharmacy, CBD Belapur, Sector-8, Navi- Mumbai - 400614,

India. E-mail: [email protected].

INTRODUCTION

Topical and transdermal products are important classes of drug delivery systems and their use in therapy is

becoming more widespread. Although topical formulations to treat ailments have existed from ancient times,

transdermal products, for which the skin is used as an alternative route for systemic and regional therapy, are

relatively new entities [1]. The purpose of topical dosage forms is to conveniently deliver drugs to a localized area

of the skin [2]. Although microemulsions can be used to deliver drugs via several routes, these versatile systems

have been extensively studied as vehicles for topical administration. Their composition and structure enables them

to incorporate greater amount of drug than other topical formulations such as ointments, creams, gels and lotions.

These systems are comparatively thermodynamically stable systems because they contain surfactant, co-

surfactant, and oil [3]. Microemulsion-based colloidal drug delivery systems have gained wide acceptance

because of their enhanced drug solubilization, thermodynamic stability, and ease of manufacture [4-7]. Delivery

of drugs using these microemulsions through skin increases the local/systemic delivery of the drug by different

mechanisms that make them suitable vehicles for the delivery of Antifungals.

ASIAN J. EXP. BIOL. SCI. VOl 1 (3) 2010 :580-591

ABSTRACT

The present study was conducted to investigate the microemulsion based topical drug delivery system of antifungal drug

Fluconazole (FLZ) in order to bypass its gastrointestinal adverse effects and to improve patient compliance. The pseudo

ternary phase diagrams were developed for combinations of Isopropyl Palmitate (IPP) or Light Liquid Paraffin (LLP) as the

oil phase, Aerosol OT as surfactant and Sorbitan Monooleate as cosurfactant using water titration method. Microemulsions

obtained were analyzed for transdermal permeability of fluconazole using Keshary-Chien diffusion cell through an excised

rat skin. Higher invitro permeation was observed from IPP based microemulsion. Thus it was selected for further formulation

studies. The developed microemulsion was characterized for optical birefringence, globule size and polydispersibility index.

The average globule size of the microemulsion was found be less than 100m. Centrifugation studies were carried out to

confirm the stability of the developed formulation. The formulation was thickened with a gelling agent carbopol 940, to yield

a gel with desirable properties facilitating the topical application. The developed microemulsion based gel was characterized

for pH, spreadability, refractive index and viscosity. Optimized formulation was then subjected to in vitro antifungal

screening in comparison to currently available marketed gel formulation of fluconazole (Flucos gel). Optimized

microemulsion based gel formulation was found to exhibit significant antifungal activity as compared to marketed

formulation. The safety of gel formulation for topical use was evaluated using skin irritation test. Thus the present study

indicates that microemulsion can be a promising vehicle for the topical delivery of fluconazole.

KEY WORDS: Fluconazole, microemulsion, microemulsion based gel, anti-fungal, Candida albicans

ORIGINAL ARTICLE

Design and Evaluation of Micro emulsion Based Drug Delivery System K.R. Jadhav, et. al

ASIAN J. EXP. BIOL. SCI. VOl 1 (3) 2010

581

Fungal infections are common in human beings, which are either topical or severe systemic infections. Invasive

fungal infections are being identified with an everncreasing frequency in prematured infants, immuno-

compromised hosts, and patient s receiving immunosuppressive agents and in those with acquired immuno-

deficiency syndrome (AIDS). The prevention of fungal infections has been improved by the antifungal agent such

as Fluconazole.

Fluconazole, a recent synthetic triazole antifungal drug widely used for the treatment of superficial and systemic

fungal infections. The drug has slight solubility in water (8mg/mL at 370C) and a melting point of 138

0C to 140

0

C. It is widely available as tablets and IV infusion. Oral administration of fluconazole often produces gastric

irritation, heartburn and vomiting and sometimes patient can develop ulceration, and there is less patient

compliance with long term therapy. Topical drug delivery system localizing the drug at skin will be much

favorable for the treatment of skin infections and symptomatic relief.

The purpose of the present study was to investigate the microemulsion based formulations for topical delivery of

fluconazole in order to by pass its gastrointestinal adverse effects and improved patient compliance.

MATERIALS AND METHODS

Materials

Fluconazole was a gift sample from CENTAUR Pharma Ltd Mumbai, India. Isopropyl palmitate, Light liquid

paraffin, sorbitan monooleate, docusate sodium, xanthan gum, sodium alginate, hydroxypropyl methylcellulose

(Methocel K4M) and carbopol 940 were purchased from S. D. Fine Chemicals, Mumbai, India. FLUCOS GEL

(0.5% w/w); manufactured by Cosme Health Care, Goa, India, was purchased from the local market. All the other

chemicals were of the analytical grade. Double distilled water was used throughout the experiment.

Methods

In vitro inherent flux study of a drug

The inherent flux of fluconazole was determined using the Keshary-Chien type diffusion cells. Full thickness

abdominal skin of albino rats (125-150 g) was used. The dermal surface of skin was carefully cleaned to remove

subcutaneous tissues and fats without damaging the epidermal surface.

The Keshary-Chien diffusion cell assembly consisted of donor and receptor compartments. The diffusion cell has

a capacity of 20 ml and effective surface area of 3.14 cm2. The receptor compartment was filled with saline

phosphate buffer [pH=7.4] with 1% Sodium lauryl sulphate . The skin was cut to a suitable size and clamped

between the two half cells of the cell. The stratum corneum part of the skin was exposed to the donor

compartment and the dermal part of the skin was facing the receptor compartment. The cells were thermostated at

37 + 1 0C and the receptor solution was stirred with a magnetic stirrer at 200 rpm.

The saturated solution of drug was placed on the skin surface in the donor compartment. Aliquots of 2 ml were

withdrawn at 0, 0.5, 1, 2, 3, 4, 5, 6 and 7 hours from the receptor compartment and it was replaced by the 2 ml of

fresh receptor medium. The amount of drug diffused across the skin was estimated by analyzing the drug

concentration within receptor medium using HPLC method.

Data Treatment

The inherent flux per cm2 (Jss) of the drugs in g/cm

2/h was given by the slope of the steady state portion of the

line in the plot of drug amount permeated/unit area of the membrane (g/cm2) Vs time (h).From the following

formula given by Aguiar et. al [8], the diffusivity coefficient was calculated.

D = h2/6tL

Where,

D = Diffusivity coefficient in cm2/h.

h = Thickness of the skin in cm

Design and Evaluation of Micro emulsion Based Drug Delivery System K.R. Jadhav, et. al.


tL = Lag time in hour [the intercept on the time axis in the plot of cumulative amount permeated (g/cm2) Vs time

(h)]

The permeability coefficient was calculated by using the following formula given by Flynn et. al [9],

Kp =Jss/Cd

Where,

Kp = Permeability coefficient in cm2/h

Jss = Steady state flux in g /cm2/h.

Cd = Saturation solubility of drug in g/ml in phosphate buffer saline pH 7.4

Formulation

A ratio of surfactant (S) (Aerosol OT) over cosurfactant (CoS) (Sorbitan monooleate) i. e. S/CoS was chosen and

the corresponding mixture was made. The following ratios were tried - 1:1, 2:1, and 3:1. At a fixed S/CoS ratio,

the (S/CoS) mixture was mixed with oil phase to give Oil:(S/CoS) weight ratios of 9:1, 8:2, 7:3, 6:4, 5:5, 4:6, 3:7,

2:8 and 1:9 [10].

Each mixture was mixed thoroughly using magnetic stirrer until a homogenous dispersion/solution was obtained.

The mixture was titrated with water at ambient temperature with constant stirring. Double distilled water was used

in the formulation so as to prevent the incorporation of surface-active impurities. After each addition of water, the

system was examined for clarity, birefringence, flow properties and stability. The end point of the titration was

the point where the solution became cloudy and/or birefringent. The quantity of the aqueous phase added when

the mixture become turbid was noted. The percentages of the three different pseudo-phases incorporated were

calculated. Same procedure was also followed for all other S/CoS ratios. Phase diagrams were prepared after

calculating the percentage of each phase required to form microemulsion.

After preparing the pseudo ternary phase diagram the medicated microemulsions were formulated. The

formulations were then characterized by using different techniques and then evaluated for their in vitro

performance. The compositions of different microemulsions for isopropyl palmitate with different S: CoS

(Aerosol OT: Sorbitan monooleate) ratios are given in the Table 1 and the compositions of different

microemulsions for light liquid paraffin with different S: CoS ratios are given in the Table 2. During formulation

of medicated microemulsions the drug was dissolved in the mixture of oil and S: CoS. This final mixture was then

titrated with water so as to get a clear and transparent microemulsion.

Characterization of Microemulsion

The formulated microemulsions were then recognized and characterized on the basis of their physical properties,

which can not only explain the performance of the system but also help in modifying their performance attributes.

The optical properties of the microdroplets, their behaviour in a gravitational field and rheological behaviour

easily differentiate them from macrodroplets.

Transparency/Translucency

The droplets of the microemulsions being smaller than th the wavelength of visible light, permit white light to

pass through the dispersed system making it transparent or translucent [11]. The microemulsion systems were

inspected for optical transparency and homogeneity by usual observation against strong light. The systems were

also checked for the presence of undissolved drug or other solid ingredient.

Globule Size Analysis of the Microemulsion

The average globule size and polydispersity index of the medicated microemulsion were determined by the

photon correlation spectroscopy. Measurements were carried at an angle of 90 at 25 C. Microemulsion was

diluted with double distilled water to ensure that the light scattering intensity was within the instruments

sensitivity range. Double distilled water was filtered through 0.45 membrane filters prior to globule size

determination.



583

Optical Birefringence

Microemulsion was placed between two polarizing plates in a series and then observed for light transmittance.

After this, one of the plates was rotated relative to the other through 90o (crossed polarizers) and then examined.

Centrifugation

This technique helps to determine behaviour of small particles in gravitational field i.e., their separation rate is

quite simple and inexpensive providing a rapid full-proof identification of the system as microemulsion.

Microemulsion systems were subjected to centrifugation at 3000 rpm for 30 minutes and then examined for any

phase separation.

Solubility Analysis

An excess amount of drug was added in test tube containing 5 ml of IPP and IPP-microemulsion. The tubes were

kept on mechanical water bath shaker (Neolab) at 320C for 72 h. The suspension was filtered through membrane

filter [0.45] .The filtrate was diluted with methanol and drug concentration was determined

spectrophotometrically at 261 nm. Identical method was followed to determine solubility of drug in LLP and LLP

microemulsion.

In Vitro Evaluation for Screening of Microemulsion

The diffusion of fluconazole from the microemulsion was investigated across the excised rat skin using the same

diffusion cell model (Keshary-Chien type diffusion cells) and the same method that was used for in vitro inherent

flux study. Full thickness abdominal skin of albino rats (125-150 g) was used. The dermal surface was carefully

cleaned to remove subcutaneous tissues and fats without damaging the epidermal surface. One-gram of drug

formulation was placed on the skin surface in the donor compartment. The amount of drug diffused across the

skin was estimated by analyzing the drug concentration within receptor medium using HPLC method. Average

values of three readings of in vitro permeation data were calculated and the average cumulative amount of drug

permeated per unit surface area of the skin was plotted versus time.

The slope of the linear portion of the plot was calculated as flux Jss (g/cm2/h) [12] and the permeability

coefficient was calculated using following formula:

Kp = Jss

Cv

Where Kp is permeability coefficient and Cv is total amount of drug.

The drug fluxes from IPP microemulsions were compared with the fluxes from LLP microemulsions.

Formulation Development of Microemulsion Based Gel

Various gelling agents namely, xanthan gum, sodium alginate, hydroxypropyl methylcellulose (Methocel K4M)

and Carbopol 940 were evaluated for their ability to gel medicated microemulsion. Gelling agent was dispersed

slowly in the medicated microemulsion with the help of overhead stirrer. In case of Carbopol 940, the dispersion

was neutralized by using triethanolamine to obtain the gel.

Characterization of Microemulsion Based Gel

Drug Content

For determination of drug content, about 1 g of the gel was weighed in a 100-ml volumetric flask and dissolved in

methanol; it was diluted appropriately and drug content was determined spectrophotometrically (261 nm).

Measurement of pH

The pH of microemulsion based gel was measured on digital pH meter standardized using pH 4.0 and 7.0

standard buffers before use.

Refractive Index

The refractive index of plain formulation and medicated formulation was determined using an Abbe-type

refractometer.



Spreadability

An apparatus suggested by Mutimer et al [13] to determine spreadability of the formulation, was modified

suitably in laboratory and used for the study. It consists of a wooden block to which a pulley is attached to one

end. A rectangular ground glass plate is fixed on the same end. An excess of microemulsion (3g) under study was

placed on ground glass plate. The microemulsion is than sandwiched between glass plate and another glass plate

having a hook to which a pan is attached at one end with the help of string. The top glass plate was subjected to a

weight of 50gm by putting weight in the pan and the time (in sec) required by the top plate to travel a distance of

10cm is noted. A shorter time interval indicates better Spreadability

Rheological Behaviour

Rheology is less precise but simpler way to identify anisotropic aggregates in the system. In microemulsion,

formation of liquid crystalline stage coincides with formation of nonspherical aggregates (cylindrical or lamellar

aggregates), which obstructs the flow in the dispersion medium. This produces high yield value. Microemulsions

being isotropic (spherical) systems offer less resistance to flow and exhibit low viscosity as compared to

macroemulsions also. Rheological properties (study of deformation and flow of matter) are required in various

pharmaceutical areas. It helps to monitor the effect of vehicles consistency on release of drug from the

preparations and subsequent percutaneous absorption. Also it is important from the manufacturing point of view.

Viscosity measurements were carried out using a Brookfield viscometer (LVT Model). 20 ml of microemulsion

was filled in the cylindrical tube and the dial reading was noted at 0.3, 0.6, 1.5, 3, 6, 12, 30, and 60 rpm. The

speed was then successively lowered and the corresponding dial readings were noted. Direct multiplication of the

dial readings with factors given in the Brookfield viscometer catalogue gave the viscosity in centipoises.

Comparison with Marketed gel of Fluconazole

The release of drug from optimized IPP microemulsion based gel was compared with that of marketed gel

containing 0.5% w/w of fluconazole and the flux (Jss) and permeability coefficient (Kp) were calculated. The

enhancement of drug penetration due to microemulsion formulation was noted as enhancement factor (EF), [14]

which was calculated using following formula:

EF = Kp (microemulsion)

Kp (marketed gel )

In Vitro Anti-fungal Studies

In vitro anti-fungal activity studies of optimized IPP formulation were carried out using fungus Candida albicans.

The antifungal activity of fluconazole from the optimum formula as well as the reference standard (marketed gel)

was determined using candida albicans (ATCC No.: 10231) as a representative fungi, using saboured dextrose

agar as culture medium adopting cup plate method. The mean inhibition zone was calculated for each plate and

this value was taken as an indicator of the antifungal activity.

A single well isolated colony of candida albicans of atleast 1mm diameter was picked from the culture plate and

was streaked aseptically to agar slant. The slant was incubated for 24 hrs at 37oC. After incubation, the inhibition

zone diameter around each well was measured using a ruler.

Histopathological investigation of skin using microemulsion formulation

The rat abdominal skin region measuring approximately 4 cm2 was mounted on modified Keshary Chien diffusion

cell. The microemulsion (3 g) was applied identical to diffusion study and the effects were compared against

water as control. The skin was fixed in 10% neutral formalin for 24 hours and then cut vertically against the

surface at the central region (4mm width). Each section was dehydrated using graded solutions of ethanol and

then embedded in paraffin wax. Tissues were divided into small pieces and stained with haematoxylin and eosin.

The sections were observed under 100 x magnifications and photographed [15].

RESULTS AND DISCUSSION



585

In Vitro Inherent Flux Study of Drug

A plot of cumulative amount permeated (g/cm2) vs. time (h) is shown in Figure 1.The results of regression

analysis are depicted in Table 3. The values for Jss, Cd, Kp, tL and D are indicated in Table 4. Thus the in vitro

inherent flux study helps to compare the above parameters with the results obtained for optimized formulation.

Table 1 Composition of Microemulsions Containing Isopropyl Palmitate as Oil Phase (S:CoS Aerosol

OT: Sorbitan Monooleate)

Table 1. a) S: CoS = 3:1

Formulation

code

Oil

(%w/w)

S:CoS

(%w/w)

Drug

(%w/w)

Water

(%w/w)

IPPF1 55.97 6.21 0.5 37.31

IPPF2 31.84 7.96 0.5 59.70

IPPF3 22.46 9.62 0.5 67.40

IPPF4 17.05 11.37 0.5 71.07

IPPF5 12.75 12.75 0.5 73.98

Table 1. b) S: CoS = 2:1

Formulation

code

Oil

(%w/w)

S:CoS

(%w/w)

Drug

(%w/w)

Water

(%w/w)

IPPF1 52.67 5.85 0.5 40.97

IPPF2 34.60 8.65 0.5 56.24

IPPF3 24.87 10.66 0.5 63.96

IPPF4 18.65 12.43 0.5 68.40

IPPF5 13.81 13.81 0.5 71.86

Table 1. c) S: CoS = 1:1

Formulation

code

Oil

(%w/w)

S:CoS

(%w/w)

Drug

(%w/w)

Water

(%w/w)

IPPF1 63.96 7.10 0.5 28.42

IPPF2 44.22 11.05 0.5 44.22

IPPF3 31.65 13.56 0.5 54.27

IPPF4 22.96 15.30 0.5 61.23

IPPF5 16.58 16.58 0.5 66.33

Table 2 Composition of Microemulsions Containing Light Liquid Paraffin as Oil Phase

(S: CoS Aerosol OT: Sorbitan Monooleate)

Table 2. a) S: CoS = 3:1

Formulation

code

Oil

(%w/w)

S:CoS

(%w/w)

Drug

(%w/w)

Water

(%w/w)

LLPF1 63.96 7.10 0.5 28.42

LLPF2 41.89 10.47 0.5 47.13

LLPF3 29.02 12.43 0.5 58.04

LLPF4 22.11 14.74 0.5 62.64

LLPF5 16.58 16.58 0.5 66.33



Table 2. b) S: CoS = 2:1

Formulation

code

Oil

(%w/w)

S:CoS

(%w/w)

Drug

(%w/w)

Water

(%w/w)

LLPF1 68.88 7.65 0.5 22.96

LLPF2 44.22 11.05 0.5 44.22

LLPF3 30.28 12.97 0.5 56.24

LLPF4 22.96 15.30 0.5 61.23

LLPF5 17.15 17.15 0.5 65.19

Table 2. c) S: CoS = 1:1

Formulation

code

Oil

(%w/w)

S:CoS

(%w/w)

Drug

(%w/w)

Water

(%w/w)

LLPF1 71.64 7.96 0.5 19.90

LLPF2 49.75 12.43 0.5 37.31

LLPF3 34.82 14.92 0.5 49.75

LLPF4 25.95 17.30 0.5 56.24

LLPF5 19.13 19.13 0.5 61.23

Table 3 Regression Parameters from In Vitro Inherent Flux Study

Regression Parameters Observed Values

Correlation coefficient 0.9195

Slope 13.999

Y- intercept 6.509

Table 4. Parameters Calculated from In Vitro Inherent Flux Study

Sr. No. Parameters Results

1 Jss (g /cm2/h) 13.999 + 0.238

2 Cd (g/ml) 9304.241 + 186

3 Kp (cm/h) (1.504 + 0.08) 10-3

4 tL (h) 0.57 + 0.075

5 D (cm2/h) (1.7894 + 0.116) 10

-4

Each Value Represents Mean + S.D., n = 3

Characterization of Microemulsion

Different compositions of formulations were tried and medicated microemulsions were formulated with 0.5%

drug. Further these formulations were characterized for transparency/translucency, globule size analysis, optical

birefringence, stability.

Transparency/Translucency

All the microemulsions formed were transparent and appeared like a homogenous single-phase liquid, when

observed for visual clarity against strong light. No traces of undissolved drug or other solid ingredient were found

in all samples.



587

Globule Size Analysis of the Microemulsion

Polydispersity indicates the uniformity of droplet size within the formulation. The higher the polydispersity, the

lower the uniformity of the droplet size in the formulation. The IPP microemulsion had globule size of 66.5 nm

and polydispersity index of 0.011. The blank IPP microemulsion had globule size of 67.9 nm and polydispersity

index of 0.051. The LLP microemulsion had globule size of 52.7 nm and polydispersity index of 0.369. The blank

LLP microemulsion had globule size of 54.2 nm and polydispersity index of 0.421. The incorporation of

fluconazole did not have considerable influence on the globule size of the microemulsion.

Optical Birefringence

The samples were examined by ocular inspection in a cross polarizer for sample homogeneity and birefringence.

The microemulsions appeared completely dark when observed under cross polarizer. The observations indicated

that all the microemulsions were optically isotropic colloidal dispersions.

Centrifugation

None of the microemulsion systems showed signs of phase separation on centrifugation at 3000 rpm for 30

minutes. This result provided a rapid and full proof identification of the system as microemulsion.

Solubility Analysis

The results of the solubility study are represented in Table 7. The solubility of fluconazole in IPP microemulsion

and in LLP microemulsion is almost 4 folds higher than that in plain IPP and LLP. Microemulsions have

solubilising ability for drugs of diverse chemical nature. These results suggest that microemulsions were found to

increase the drug solubility. The increase solubility is expected to enhance the performance of formulations.

In Vitro Evaluation for Screening of Microemulsion

When in vitro release studies of formulations through rat skin were carried out, the flux of drug from the

formulations of IPP (Table 8) was found to be greater as compared to formulations LLP (Table 9). This was

because of higher solubility of fluconazole in IPP and S: CoS mixture as found in solubility studies. Hence, IPP

microemulsions were selected for further studies.

Formulation Development of Microemulsion Based Gel

Microemulsions have lower viscosity and are difficult to apply on skin so for the ease of application they are tried

to be gelled with suitable gelling agent. Various gelling agents such as xanthan gum, sodium alginate,

hydroxypropyl methylcellulose and Carbopol 940 were evaluated for the gelling of fluconazole microemulsion.

The fluconazole microemulsion used for this purpose contained 0.5% (w/w) fluconazole. The concentration of the

fluconazole was selected to enable comparative evaluation with the currently marketed 0.5% (w/w) fluconazole

formulations (Flucos gel). It was observed that sodium alginate affected the structure of the microemulsion and

resulted in separation of oily phase. This observation could be attributed to that fact that salts like sodium alginate

can affect the structure of the microemulsion86. Xanthan gum and hydroxypropyl methylcellulose was unable to

yield gels of acceptable consistency. Only Carbopol 940 at a concentration of 1 %w/w was able to thicken the

microemulsion, could yield gel consistency without disturbing the microstructure of the fluconazole

microemulsion. Hence, Carbopol 940 was selected for the formulation of MBG

Characterization of Microemulsion Based Gel

Drug content

Fluconazole content in the gel was found to be 99.36 1.06 % of the theoretical value (0.5%w/w)

Measurement of pH

The pH of microemulsion based gel systems was found to be in the range of 7.0 to 8.0

Refractive Index

The values of the refractive index of medicated formulations and plain formulations showed that there were no

significant differences between the values. (Table 5) Therefore, it can be concluded that the formulations were



chemically stable and remained isotropic; thus, there were no interactions between formulation excipients and

drug.

Spreadability

The rheological properties of topical preparations influence the performance of drug delivery systems. The

spredability is important for uniform and ease of application of topical preparation from patient compliance point

of view. It was found in the range of 8 to 15 sec for different formulations which indicates good spreadability.

Table 5 Comparative refractive index of plain and medicated IPP MBG

Refractive Index

Medicated Formulation Plain Formulation

IPP MBG 1.685 0.007 1.680 0.005

Each Value Represents Mean + S.D., n = 3

Rheological Behaviour

Viscosity

Rheological behavior of the microemulsion based gel systems indicated that the systems were non -Newtonian in

nature showing decrease in viscosity at the increasing shear rates. The viscosity data has been summarized in

Table 6. There was no significant difference found between the viscosities of plain and medicated microemulsion

based gels (Fig. 2).

Table 6 Comparative viscosity of plain and medicated IPP MBG

Sr. no Spindle speed Viscosity of plain MBG Viscosity of medicated

MBG

1. RPM centipoise centipoise

2. 0.3 44000 42000

3. 0.6 27000 25000

4. 1.5 14000 12000

5. 3 9000 8000

6. 6 5700 5000

7. 12 3800 3400

8. 30 2320 2200

RPM - Revolutions per Minute

Composition of Optimized Formulation

The results obtained from the flux studies helped to select the formula with maximum flux for further studies. The

composition of the final formulation was: Oil (34.60% w/w), S: CoS (8.65%w/w), Water (56.24%w/w) and

fluconazole (0.5%w/w).

Table 7 Solubility data of fluconazole in plain oils and their corresponding microemulsion system

Solvent Solubility [mg/ml]

IPP 4.2490.172

LLP 3.4240.152

IPP-Microemulsion (IPP-ME) 14.9460.18

Each value represents mean S.D. (n = 3).

Comparison of Optimized Formulation with Gel Cream

When the release of optimized formula was compared with the 0.5% marketed formulation (Flucos gel), the

optimized microemulsion based gel showed the higher flux as compared to the marketed formulation (Fig 3).

Table 8 In Vitro Skin Permeation Study for IPP Microemulsion



589

The results showed that the fluconazole has the higher flux as compared to marketed flucos gel and in vitro

inherent flux of flurconazole in saline phosphate buffer (pH 7.4). The permeability enhancement factor for

microemulsion based gel when compared with marketed formulation was found to be 2.196 and that of

microemulsion based gel and flucos gel compared with drug dispersion in saline phosphate buffer was found to be

5.4260 and 2.4704 respectively (Table 10).

Table 9 In Vitro Skin Permeation Study for LLP Microemulsion

Formulations Flux (+ SD) (g/cm2/hr) Permeability coefficient (cm

2/hr)

F1 102.92 + 2.59 20.584

F2 124.70 + 4.28 24.94

F3 73.32 + 2.54 14.664

Table 10 Comparison of Optimized Formulation with Marketed Gel and Drug Dispersion

Formulation Flux

(g/cm2/h)

Permeability

Coefficient

(cm2/h)

Enhancement

Factor

(Compared

with

Marketed gel )

Enhancement Factor

(Compared with

Drug Dispersion

(Buffer pH 7.4 )

Microemulsion Based Gel 40.82 8.164 2.196 5.4260

Marketed gel 18.588 3.717 - 2.4704

Drug Dispersion (Buffer

pH 7.4)

13.999 1.5046 - -

Table 11 Comparative zone of inhibition of reference and test

Sample Zone of Inhibition (cm)

1 2 3 4 5

Mean

Reference 3.0 2.4 2.5 2.6 3.1 2.72

Test 3.6 3.1 3.2 3.6 3.8 3.46

Antifungal activity

Results summarized in Table 11 show that mean zone of inhibition (the antifungal activity) of the tested MBG is

large than the reference standard (marketed gel). It is noted that the plain MBG diluted with the diethyl ether

showed no antifungal activity. The students t-test shows that there is a significant difference in the MBG zone of

inhibition in comparison to the reference standard at p < 0.05 where calculatedt value is higher than the

tabulated t value. The increase in antifungal activity of the fluconazole in formulation may be because of the

surfactant action and oil phase which may help in diffusion of drug.

Formulations Flux (+ SD) (g/cm2/hr) Permeability coefficient (cm

2/hr)

F1 112.35 + 3.51 22.47

F2 153.25 + 4.79 30.65

F3 108.98 + 2.42 21.796



Figure 1 Plot of Cumulative Amount Figure 2 Comparative viscosities of IPP

Permeated (g /cm2) Vs Time (h) medicated and plain MBG

Figure 3 Comparison of Optimized Formulation with Marketed Gel and Drug Dispersion

Histopathological Investigation of Skin Using ME Formulation

The histology of excised rat skin in control and treated with optimized microemulsion after 24 hours is shown in

Figure 4.1 and Figure 4.2 respectively. The microscopic observations indicate that the optimized microemulsion

has no significant effect on the microscopic structure of the skin. The surface epithelium lining and the granular

cellular structure of the skin were totally intact. No major changes in the ultra structure of skin morphology could

be seen and the epithelial cells appeared mostly unchanged.

IPP is widely used in cosmetics and topical formulations and is generally regarded as nontoxic. Aerosol OT used

in the formulation is GRAS (Generally Recognized as Safe) listed and it has been included in the FDA Inactive

Ingredients Guide for IM injections, oral capsules, suspensions and tablets and also topical preparations.

Figure 4.1 Histopathology Control Sample Figure 4.2 Histopathology Test Sample

SUMMARY AND CONCLUSION

0

20

40

60

80

100

120

0 2 4 6 8

Time (hrs)

Cumu.Amt.Released

(g/cm2)

0

10000

20000

30000

40000

50000

0 50 100

Spindle speed in rpm

Viscosity in cp

IPP medicated

MBG

IPP plain MBG

0

50

100

150

200

250

0 5 10

Time (h)

Cumulative

Amt.Released (g/cm2)

Marketed Gel

Microemulsion

Based Gel

Drug Dispersion

in Buffer (pH 7.4)



591

Microemulsion based gel formulation containing fluconazole was prepared with the aim of achieving maximum

release through the skin thus by passing its gastrointestinal adverse effect. Thus a microemulsion based gel

formulation was successfully prepared using isopropyl palmitate or light liquid paraffin, aerosol OT as surfactant,

sorbitan monooleate as cosurfactant, water and carbopol 940 as a gelling agent. Solubility study showed

fluconazole has higher solubility in microemulsion compared to in their corresponding plain oils. This leads to

increased drug loading. The flux of IPP based ME was better than LLP based ME in the in vitro release studies.

Thus IPP based ME was selected for gel formulation. The developed gel formulation showed higher flux as

compared to marketed gel and in vitro inherent flux study. In the skin irritation study the formulation was found

to be safe as indicated by histopathological findings. The in vitro anti fungal activity of fluconazole from

microemulsion based system was good as compared to that of marketed gel. Therefore the microemulsion based

gel of fluconazole was prepared to obtain improved patient compliance. Hence an attempt was made to increase

the skin permeation of fluconazole and skin tolerability.

ACKNOWLEDGEMENT

We would like to thank Centaur pharma Ltd, Mumbai for providing gift sample of fluconazole.

REFERENCES

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[11] Martin MR (1990) Emulsions, In: Theory and Practice of Industrial Pharmacy, Lea and Febiger: Varghese, pp. 503.

[12] Li GL, Geest RV, Chanet L, Zanten EV, Danhof M and Bouwstra JA (2002). J Control Rel., 84:4957.

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CORRESPONDENCE TO AUTHOR: S.L. Shetye, Department of Pharmaceutics, Bharati Vidyapeeths College of

Pharmacy, CBD Belapur, Sector-8, Navi- Mumbai - 400614, India. E-mail: [email protected]

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