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 Table of Contents  
ORIGINAL ARTICLE
Year : 2017  |  Volume : 10  |  Issue : 3  |  Page : 303-310

Formulation and characterization of oxiconazole-loaded emulgel for topical application


Department of Pharmaceutics, KLE University College of Pharmacy Belagavi, KLE Academy of Higher Education and Research, Belagavi, Karnataka, India

Date of Web Publication5-Sep-2017

Correspondence Address:
A P Gadad
Department of Pharmaceutics, KLEU'S College of Pharmacy, Belagavi, Karnataka
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/kleuhsj.ijhs_259_16

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  Abstract 


Background: Oxiconazole nitrate is a new topical broad spectrum antifungal agent used to treat superficial fungal infections. It has a low aqueous solubility due to which different techniques are employed to enhance its bioavailability. Emulgel has emerged as one of the most interesting topical drug delivery system for hydrophobic drugs like Oxiconazole as it has dual release control systems i.e. emulsion and gel.
Objective: In the present work an attempt was made to prepare Emulgel of Oxiconazole nitrate for enhancing its topical delivery.
Materials and Methods: Emulgel formulations were characterized by various parameters like pH, viscosity, spreadability, extrudability, in vitro drug release. Skin irritation test on wistar rats and in vitro antifungal test on Candida albicans were performed.
Results: Optimized formulation F5 showed 92.06% release at the end of 12 hrs. It showed no skin irritation and observed with maximum zone of inhibition when compared with marketed cream of Oxiconazole nitrate.
Conclusion: The optimized emulgel formulation F5 showed better antifungal activity in comparison to the marketed formulation.

Keywords: Emulgel, hydrophobic drug, oxiconazole nitrate


How to cite this article:
Gadad A P, Magdum AP, Dandagi P M, Bolmal U B, Kamat S. Formulation and characterization of oxiconazole-loaded emulgel for topical application. Indian J Health Sci Biomed Res 2017;10:303-10

How to cite this URL:
Gadad A P, Magdum AP, Dandagi P M, Bolmal U B, Kamat S. Formulation and characterization of oxiconazole-loaded emulgel for topical application. Indian J Health Sci Biomed Res [serial online] 2017 [cited 2019 Oct 20];10:303-10. Available from: http://www.ijournalhs.org/text.asp?2017/10/3/303/213995




  Introduction Top


Oxiconazole is a broad spectrum imidazole antifungal agent. It has also been shown to inhibit DNA synthesis and suppress intracellular concentration of adenosine triphosphate. Like other imidazole antifungal, it can increase membrane permeability to zinc, augmenting its cytotoxicity.[1] It is a biopharmaceutical classification system Class II drug having low aqueous solubility and poor systemic absorption. The major drawback of this drug is low aqueous solubility and its hydrophobic nature. Hence, different techniques are employed to enhance the solubility of this poorly water soluble drug which includes use of surfactants, cosurfactants, cosolvents, etc.[2] Topical drug delivery systems have been used for centuries for the treatment of local and systemic action. Transparent gels are widely used nowadays in cosmetics as well as in pharmaceutical preparations. Inspite of having many advantages of gels, a major limitation is in the delivery of hydrophobic drugs.[3] Emulsion is an excellent vehicle for hydrophobic drug but is thermodynamically unstable. Emulgel provides a better vehicle for delivery of hydrophobic drugs such as oxiconazole as it increases their solubility and offers a dual-controlled release effect due to incorporation of two systems, i.e., emulsion and gel. The disadvantage of gel and emulsion is overcome in the approach of emulgel which is the combination of both. Emulgel is greaseless, spreads easily, thermodynamically stable, have long shelf life and offers a better patient compliance.[4]

The aim of the present study was to formulate and evaluate emulgel of oxiconazole using different gelling agents, and formulations were evaluated for various parameters such as pH, viscosity, drug content, in vitro drug release, spreadability, and extrudability.


  Materials And Methods Top


Materials

Oxiconazole was obtained as gift sample from Harman Finochem Pvt., Ltd., Aurangabad. Carbopol 981 was purchased from Lubrizol, Mumbai. Tween 20, Span 20, propylene glycol (PEG), carbopol 940, methylparaben were purchased from Hi-Media Pvt., Ltd., Mumbai. Methanol and triethanolamine were purchased from SD Fine Chem. Pvt., Ltd., Mumbai. Glycerol was purchased from Ranbaxy, Mumbai. Propylparaben was purchased from Priya research labs, Bangalore.

Methods

Preformulation study

In preformulation study for authentication of drug, melting point of oxiconazole was determined by capillary tube method.

Compatibility of oxiconazole nitrate with polymers and excipients was established by infra-red (IR) analysis. IR spectral analysis of the sample (drug, polymers, and a mixture of the drug with each of the polymer) was carried out by potassium bromide method.[5]

Differential scanning calorimetry (DSC) analysis was performed on DSC 60 detector (Shimadzu, Co., Japan). Approximately 5 mg of oxiconazole and the physical mixture of oxiconazole with Carbopol 981 and Carbopol 940 was weighed into an aluminum pan and sealed. DSC scan was recorded from 30°C to 300°C at a heating rate of 10°C/min under a nitrogen purge, using an empty pan as a reference.

Saturation solubility of oxiconazole nitrate was measured in various oils, namely, castor oil, liquid paraffin oil, oleic acid, and olive oil. Saturation solubility of oxiconazole nitrate was measured in various surfactants, namely, Span 20, Span 80, Tween 20, Tween 60, and Tween 80. Saturation solubility of oxiconazole nitrate was measured in various cosurfactants, namely, PEG 400, PEG, and PEG 600.[6]

Preparation of emulsion

The required quantity of oxiconazole nitrate was dissolved in surfactant, cosurfactant, and oil. The oil phase of the emulsion was prepared by dissolving Span 20 in light liquid paraffin, and aqueous phase was prepared by dissolving Tween 20 in purified water. Both the oil phase and aqueous phase were separately heated to 70°C–80°C, then the oil phase was added into the aqueous phase with continue stirring until it cools to room temperature. The obtained emulsion was mixed with gel at 1:1 ratio with continuous stirring to obtain the emulgel.[7] The gel base was prepared by soaking the gelling agent overnight in a sufficient quantity of water, and then, the emulsion equivalent to 1% of oxiconazole nitrate was incorporated in the gel base to give the emulgel.[8] Emulgel was formulated as per the formulation table as shown in [Table 1].
Table 1: Formulation table of emulgel

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Evaluation of emulgel

The formulated emulgel was characterized for its physicochemical properties and was evaluated for drug content, in vitro studies, and antifungal studies.

Physicochemical evaluation of emulgel

Appearance

The prepared emulgel formulations were inspected visually for their color, homogeneity, and consistency [Table 2].[9]
Table 2: Evaluation parameters of oxiconazole nitrate emulgel

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Photomicroscopy

Optimized formulation F5 emulgel was viewed under a trinocular microscope to study the globular structure in gel. The emulgel was suitable diluted, mounted on glass slide, and viewed under Trinocular microscope [Figure 1].
Figure 1: Microphotograph of optimized F5 formulation

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Drug content

One gram of emulgel was weighed and diluted up 50 ml using phosphate buffer pH 6.8 in 50 ml volumetric flask. Five milliliters was pipetted out in 25 ml volumetric flask, and the volume was made up using phosphate buffer pH 6.8. Then, the absorbance was measured using ultraviolet spectrophotometer at 212 nm. Drug content was calculated using slope and the intercept obtained by linear regression analysis of standard calibration curve.[10]

pH

The pH of various emulgel formulations was determined using digital pH meter. It was calibrated before use. The measurement of pH of each formulation was done in triplicate, and average values were calculated.

Viscosity

The measurement of viscosity of the prepared gel was done using Brookfield viscometer cap 2000+. The gels were rotated at 50 rpm, and the corresponding dial reading was noted. The viscosity of the gel was obtained by that reading. The viscosity was measured in cps. Experiments were carried out in triplicates.

Spreadability

Three hundred and fifty milligrams of emulgel was weighed, and then, it was taken on the glass plate (10*5). Another glass plate was dropped at the height of 5 cm. Then, the diameter of circle was measured after 1 min. The test was performed in triplicate, and average values were calculated.

Extrudability

The extrudability test is based on the determination of weight required to extrude 0.5 cm ribbon of emulgel in 10 s from lacquered collapsible aluminum tube. The test was performed in triplicate, and the average values were calculated. The extrudability was then calculated using the following formula.[11]



In vitro release study

The in vitro drug release studies of the emulgel were carried out in modified Franz Diffusion cell using dialysis membrane. The membrane was soaked in phosphate buffer of pH 6.8 for 9–12 h, was clamped carefully between the donor and receptor compartment. Then, emulgel (1 g) was spread uniformly on the dialysis membrane. A volume of 40 ml of the phosphate buffer of pH 6.8 was used as dissolution media which was added to the receptor compartment. The donor compartment was kept in contact with receptor compartment. This whole assembly was kept on a magnetic stirrer, and the solution on the receptor side was stirred continuously using a magnetic bead, and temperature of the cell was maintained at 37° ± 0.5°. Sample (1 ml) was withdrawn at suitable time intervals and replaced with the equal amount of fresh dissolution media. Samples were analyzed spectrophotometrically at 212 nm, and the cumulative % drug release was calculated. The graph is plotted between cumulative % drug releases versus time [Figure 2], [Figure 3], [Figure 4].[12]
Figure 2: In vitro drug release of formulations F1–F3

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Figure 3: In vitro drug release of formulations F4–F6

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Figure 4: In vitro drug release of formulations F7–F9

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Kinetics of drug release

One of the most important and challenging areas in the drug delivery field is to predict the release of the active agent as a function of time using both simple and sophisticated mathematical models. The importance of such models lies in their utility during both the design stage of a pharmaceutical formulation and the experimental verification of a release mechanism. To identify a particular release mechanism, experimental data of statistical significance are compared to a solution of the theoretical model. To analyze the mechanism for the release and release rate kinetics of the dosage form, the data obtained was fitted into zero-order, first-order, Higuchi matrix, and Korsmeyer-Peppas model. By comparing the R2 values obtained, the best-fit model was selected.[13]

Skin irritation test

The skin irritation test was performed on the male Wistar rats. The animals were divided into three groups, i.e. control, standard, and test. The back skin of the rat of 4 cm 2 was shaven 1 day before the start of the study. After 24 h of shaving the skin of the rat, the standard group was applied with marketed formulation and the test group was applied with the optimized formulation F5 and the rats were observed for any irritation at the end of 24 h. The animals were observed for any skin irritation such as erythema or edema and score was given accordingly.[14]

In vitro antifungal study

Weighed 16.25 g of sabouraud dextrose agar was transferred in a 500 ml of conical flask and 250 ml of purified water, and heat was applied to dissolve it completely. It is then sterilized for 15 min at 121°C and 15 lb pressure in an autoclave. It was then cooled to room temperature, and the fungal strain (Candida albicans) was dispersed in the medium. The medium was then poured into three  Petri dish More Detailses and allowed to cool for some time at room temperature until it solidifies. After that, three cups were bored in each Petri dish with the help of sterile steel bore of 6 mm and calculated concentration of the marketed cream (oxiconazole), emulgel formulation (F5), and placebo gel were placed in the bores, and the Petri plates were incubated for 72 h at 37°C. The zone of inhibition was observed.[15]


  Results And Discussion Top


A successful attempt was made to formulate emulsion incorporated gel of oxiconazole nitrate. This formulation was developed by preparing emulsion of the drug with light liquid paraffin as oil phase, Tween 20, Span 20 as surfactant, and PEG as cosurfactant, respectively, and then incorporated into different gelling agents. Total nine emulgel formulations were prepared.

Preformulation studies

Identification of pure drug

Melting point determination

The melting point of the obtained drug sample was found to be 143°C, and it complies with the standards (141°C–143°C) indicating that the drug sample is pure.

Infrared spectroscopy

The Fourier transform infrared spectroscopy (FTIR) spectrum of the obtained sample of oxiconazole nitrate recorded by FTIR spectrometer was compared with standard functional group frequencies of oxiconazole Nitrate. The functional group frequencies of the obtained sample of the drug were found in the reported range indicating that the obtained sample was oxiconazole nitrate.

Compatibility studies

Fourier transform infrared spectroscopy

All the important functional group frequencies for oxiconazole nitrate were present in the spectral peaks of the mixture, indicating compatibility of drug with the polymers.

Differential scanning calorimetry studies

The pure oxiconazole showed sharp endotherm at 143°C corresponding to its melting point. There was no appreciable change in the melting endotherms of oxiconazole in physical mixture (oxiconazole + carbopol 981 and 940) which indicates that the drug and polymer were compatible.

Standard calibration curve

Standard calibration curve of oxiconazole nitrate in phosphate buffer pH 6.8

The curve was found to be linear in the Beer's range between 4 and 14 μg/ml at 212 nm. The correlation coefficient (R2) obtained was 0.995, and equation was y = 0.024x + 0.002.

Saturation solubility in oils, surfactant, and cosurfactant

Screening of oils, surfactant, and cosurfactants was done on solubility basis. The oil, surfactant, and cosurfactants which were able to solubilize maximum amount of drug were selected for the study. The solubility of oxiconazole nitrate was done in various oils, namely, oleic acid, olive oil, castor oil, and light liquid paraffin. Light liquid paraffin showed maximum solubility of 85 mg/ml. The various surfactants used for solubility studies were Span 20, Span 80, Tween 20, Tween 60, and Tween 80. Cosurfactants used were PEG 400, PEG 600, and PEG. The maximum solubility among surfactants was found in case of Tween 20, i.e., 65 mg/ml and case of cosurfactants PG, i.e., 135 mg/ml. Hence, depending on the maximum solubility of the drug, light liquid paraffin was selected as oil phase. Tween 20 and span 20 were selected as surfactant, whereas PEG was selected as cosurfactant for the preparation of emulsion.

Preparation of emulgel

The gelling agent was soaked in distilled water for 24 h. The oxiconazole-loaded emulsion was slowly added to the viscous solution of gelling agent by continuous stirring, and then, clear emulgel was obtained. The carbopol as an aqueous gel matrix is a continuous phase, and the dispersion of oily droplets within the meshes of a three-dimensional network of gel increases the viscosity of emulsion significantly. In the preparation of emulgel, the quantity of emulsion was added which is equivalent to 1% of drug in the final formulation 0.02 triethanolamine was added to adjust pH of formed emulgel and the preservatives were also added.

Characterization of emulgel

Physical appearance

All formulations were white in appearance and showed good homogeneity and consistency.

Photomicroscopy

The optimized emulgel formulation F5 showed good consistency. The photomicroscopic evaluation showed the presence of spherical globules has indicated formulation of emulsion in gel base. This indicates the successful method employed in the preparation of emulgel.

Drug content

The percentage drug content of all the formulations was found to be in the range of 88.11%–92.23%. The highest drug content was found in the optimized formulation F5 containing 1.0% Carbopol 981.

pH

Skin compatibility is the primary requirement for a good topical formulation. It was found that the pH of all the emulgel formulations was in the range of 6.46–6.60 that suits the skin pH indicating the skin compatibility.

Viscosity

The viscosity ranged between 486 and 596 cps. Low viscosity was found for the F5 formulation containing low concentration, i.e., 1.0% of Carbopol 981 polymer which is low viscosity polymer and the addition of emulsion. It was found that as polymer concentration increases viscosity also increases. The F5 emulsion formulation contains the larger amount of surfactant so higher the concentration of surfactant and lower the concentration of gelling agent lower the viscosity.

Spreadability

The therapeutic efficacy of formulation depends on its spreading coefficient. The value of spreadability of all emulgel formulations ranged from 4.1 to 4.9 g cm/s. Spreadability depends on the viscosity of the gel and concentration of the polymer. The formulation F5 having viscosity 486.6cPs has high spreading coefficient of 4.9 g cm/s, and the formulation F4 has lesser spreading coefficient of 4.3 g cm/s as its viscosity is 486.6 cps. The values of spreadability indicate that the gel is easily spreadable with minimal of shear.

Extrudability

The extrudability gives the extent to which a semisolid formulation is extruded out from the tube. The extrudability depends on the viscosity and consistency of formulation. The less the viscosity, the more the extent to which the formulation is extruded out. The extrudability of formulations ranged from175 to 215.75 g/cm 2. The formulation F5 had extrudability value of 175 g/cm 2. The viscosity of the formulation was 486.6 cps, and the least extrudability was found in the case of formulation F2 having viscosity of 591.1 cps.

In vitro drug release

The percentage cumulative drug release of all the prepared emulgel formulations ranged from 88.69% to 92.06% at the end of 12 h. Maximum drug release was observed in the formulation F5 after 12 h. The reason for maximum release may be the concentration of emulsifying agent or surfactant, the more the concentration of emulsifying agent better is the release. Another reason for maximum release could be the use of Carbopol 981 polymer used as a gelling agent in F5 formulation which has lower viscosity compared to other formulations. The viscosity is inversely related to the release, so as the viscosity increases release rate decreases. The cumulative drug release of optimized formulation was also compared with the cumulative drug release of topical marketed formulation containing oxiconazole nitrate. The cumulative percentage drug release was found to be 78.28% and that of the optimized formulation was found to be 92.22% at the end of 12 hrs as shown in [Table 3]. The optimized F5 formulation showed better release than marketed formulation at the end of 12 hours shown in [Figure 5].
Figure 5: Comparative in vitro release profile of marketed formulation and optimized F5 formulation

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Table 3: Comparative in vitro release profile of marketed and optimized formulation

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Kinetic study of in vitro release data

The release data was fitted into various kinetic models to calculate the release constant and regression coefficients(R 2) as shown in [Table 4]. The formulations followed matrix model except for F2, F3, F4, and F5 which followed Peppas model. In case of Korsmeyer–Peppas model, if n value is less than 0.5, it shows fickian diffusion release, and if n value is between 0.5 and 0.89, it follows nonfickian (anomalous) behavior, i.e., drug release is both diffusion and erosion-controlled mechanism. The optimized formulation shows the Peppas as the best-fit model with nonfickian anomalous behavior as n value is 0.3460.
Table 4: In vitro release kinetics for formulation F1-F9

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Skin irritation test

The Wistar rats were used for the skin irritation test. The control group was not applied with any formulation, the standard group was applied with the marketed formulation, and the test group was applied with optimized formulation F5, and it is observed for irritation at the end of 24 h. All groups did not show any irritation at the end of 24 h. Since no irritation persists, the optimized formulation passes the skin irritation test [Figure 6], [Figure 7], [Figure 8], [Figure 9].
Figure 6: Skin irritation study of control group. (a) Control group after shaving. (b) Control group after 24 h

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Figure 7: Skin irritation study of standard group. (a) Standard group after application of marketed formulation. (b) Standard group after 24 h of application

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Figure 8: Skin irritation study for test group. (a) Test group after application of optimized formulation. (b) Test group after 24 h

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Figure 9: In vitro antifungal results showing zone of inhibition. Zone of inhibition. (A) (Optimized formulation) =30 mm. (B) (Marketed formulation) = 24 mm. (C) (Placebo) =0 mm

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In vitro antifungal study

In vitro antifungal activity of optimized emulgel formulation F5, marketed formulation, and placebo were determined by cup-plate method using C. albicans as test organisms, and zone of inhibition was measured and compared. Formulation F5 showed a greater zone of inhibition, i.e. 30 mm when compared with that of marketed formulation, i.e. 24 mm and placebo showed no zone of inhibition.

Future scope

Future work can be taken up with respect to

  • In vivo safety and efficacy
  • Stability studies to characterize the delivery system for clinical use.



  Conclusion Top


In the present study, an attempt was made to formulate emulgel of oxiconazole nitrate for topical delivery, and it was further evaluated for various parameters such as pH, viscosity, spreadability, extrudability, and in vitro drug release. IR spectra and DSC thermograms revealed that polymers and drug were compatible. Emulgel formulation F5 showed promising results with respect to the spreadability, viscosity, in vitro drug release, and were selected as optimized emulgel formulation.

The optimized emulgel formulation showed better antifungal activity in comparison to the marketed formulation. The optimized formulation, i.e. F5 did not show any skin irritation on the Wistar rats, so the emulgel formulation passes the skin irritation test. From the above results showed that oxiconazole nitrate emulgel was successfully formulated.

Acknowledgment

We are thankful to Harman Finochem Pvt., Ltd., Aurangabad, for providing oxiconazole as gift sample. We are thankful to Principal, KLEU COP, Belagavi, for providing necessary facilities to carry out the research project.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4]



 

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