1. INTRODUCTION:

Emulgel are emulsions, either of the water-in-oil or oil-in-water type, which are gelled by mixing with a gelling agent. The emulsion also acts as controlled release drug delivery system in which drug particles entrapped in internal phase go through the external phase to the skin and slowly get absorbed^1,2.

Oxiconazole is used to treat skin infections such as athlete's foot, jock itch and ringworm. Oxiconazole possesses poor water solubility and highly hydrophobic in nature that lies in Biopharmaceutical classification system (BCS)-II class which pose problems in its delivery at the topical region, hence the formulation of Oxiconazole emulgel appeared to be a viable approach.

Literature on topical formulation of Oxiconazole is very less^2,3. But the marketed products include only the creams and lotions. Hence there is a scope for developing Oxiconazole emulgel formulation.

2. MATERIALS AND METHODS:

Materials:

Oxiconazole Nitrate was obtained as a gift sample from Metrochem API Private Limited, Hyderabad. Light liquid paraffin, Tween 80 and Cetostearyl alcohol were purchased from Sd Fine Chem Limited, Mumbai. Clove oil was purchased from Loba Cheme Pvt. Limited, Mumbai. Span 80 was purchased from Qualikems Fine Chem Pvt. Limited. Methyl paraben, Carbapol 934 and HPMC K4M were purchased from Rolex Chemical Industries, Mumbai. Benzoic acid, Gluteraldehyde, Potassium dihydrogen phosphate and Hydrochloric acid were purchased from Molychem, Mumbai. Ethanol and Methanol were purchased from Merck Company, Mumbai. Triethanolamine was purchased from Qualigens Fine Chemicals, Mumbai. Sodium hydroxide was purchased from Himedia Company, Mumbai. All ingredients used were of analytical grade.

Experimental Methods:

I. Preformulation Studies:

Preformulation testing is an investigation of physical and chemical properties of a drug substance alone and when combined with excipients^4,5.

a) Solubility analysis:

Solubility was quantitatively determined by adding drug in small increments to a test tube containing fixed quantity of solvent.

b) Melting point determination:

Melting point of Oxiconazole nitrate was determined by using melting point apparatus⁶.

II. Estimation of oxiconazole by spectrophotometric method:

A Spectrophotometric method based on the ion pair complexation between drug and methyl orange followed by extraction of drug with dichloromethane, then measurement of extinction at 427 nm using UV-Visible Spectrophotometer was used in the present study for the estimation of Oxiconazole^7,8.

Standard curve of oxiconazole nitrate:

i) Preparation of standard solution of oxiconazole:

50mg of Oxiconazole nitrate was accurately weighed and transferred to a 50ml volumetric flask. 50ml of methanol was added to it. Then the solution was makeup to the final volume with methanol to give a final concentration of 1mg/ml.

ii) Preparation of working standard solution of Oxiconazole:

From the stock solution, different aliquots of 0.05, 0.1, 0.15, 0.2, 0.25, 0.3ml were taken and diluted up to 10ml with pH 6.8 phosphate buffer to give concentrations of 5 µg/ml, 10µg/ml, 15µg/ml, 20µg/ml, 25µg/ml, 30 µg/ml of Oxiconazole respectively.

iv) Procedure:

In a separator funnel, aliquots of 2µg solution of Oxiconazole nitrate (total 10ml) was added to 3ml 0.1 M citric acid solution (pH 2.3). Then, 2ml of 0.1% w/v Methyl orange in 40% aqueous methanol (v/v) was added. The reaction mixture was extracted by shaking with 10ml of dichloromethane. Then absorbance of the resulting solution was measured in UV visible spectrophotometer at 427nm against a reagent blank prepared in the same manner without the addition of the drug. Repeat the same procedure for remaining concentrations and measure the absorbance values. The graph of concentration versus absorbance was plotted^{9 - 11}.

Table No. 1: Composition of Oxiconazole Emulgel

S. No	Ingredients (% w/w)	Purpose	F1	F2	F3	F4	F5	F6
1	Oxiconazole	Drug	1%	1%	1%	1%	1%	1%
2	Carbapol 934	Polymer	0.25	0.5	0.75	-	-	-
3	HPMC K4M	Polymer	-	-	-	0.25	0.5	0.75
4	Liquid paraffin	Oily phase	2.5	2.5	2.5	2.5	2.5	2.5
5	Tween 80	Emulsifier	0.3	0.3	0.3	0.3	0.3	0.3
6	Span 80	Emulsifier	0.5	0.5	0.5	0.5	0.5	0.5
7	Propylene glycol	Humectant	2.0	2.0	2.0	2.0	2.0	2.0
8	Cetostearyl alcohol	Emollient	0.1	0.1	0.1	0.1	0.1	0.1
9	Clove oil	Permeation enhancer	0.2	0.2	0.2	0.2	0.2	0.2
10	Methyl paraben	Preservative	0.01	0.01	0.01	0.01	0.01	0.01
11	Glutaraldehyde	Preservative	0.05	0.05	0.05	0.05	0.05	0.05
12	Ethanol	Solvent	2.0	2.0	2.0	2.0	2.0	2.0
13	Benzoic acid	Preservative	0.01	0.01	0.01	0.01	0.01	0.01
14	Purified water	Aqueous solvent	Q.S	Q.S	Q.S	Q.S	Q.S	Q.S

Different formulations of Oxiconazole emulgels were prepared using carbapol 934 and HPMC K4M as gelling agents with varying concentrations¹². The gel in formulations were prepared by dispersing carbopol 934 and HPMC separately in to the purified water with constant stirring at a moderate speed then the pH was adjusted to 6.5 using tri ethanol amine^13,14.

The oily phase of emulsion was prepared by dissolving span 80, cetostearyl alcohol in light liquid paraffin while the aqueous phase was prepared by dissolving tween 80, methyl paraben, benzoic acid and propylene glycol in purified water whereas Oxiconazole drug was dissolved in ethanol and mixed with the aqueous phase^15,16. Both oily and aqueous phases were separately heated to 70 – 80^°C and then the oily phase was added to the aqueous phase with continuous stirring until cooled to room temperature^17-19. Add glutaraldehyde during mixing of gel and emulsion in ratio 1:1 to obtain the emulgel.

3. Evaluation of Oxiconazole Nitrate Emulgel:

a) Physical appearance:

The emulgel preparations are tested visually for their colour, homogeneity, consistency and also for phase separation.

b) Determination of p^H:

p^H of the emulgel was determined by using digital p^H meter. The p^H meter electrodes should be washed with sterile water and then the p^H electrodes dipped in to emulgel formulation to measure the p^H and repeat this process three times²⁰.

c) Spreadability test:

A sample of 0.5g of each formula was pressed between two slides (divided into squares of 5 mm sides) and left for about 5 minutes where no more spreading was expected. Diameters of spreaded circles were measured in cm and were taken as comparative values for spreadability²¹. The results obtained are average of three determinations.

d) Measurement of Viscosity:

The viscosity of the developed emulgel formulations was determined by using a cone and plate type of Brookfield viscometer (Brookfield viscometer RVT) with spindle No.7. The maximum shear rate was 100 rpm while minimum shear rate was 10rpm.

e) Content uniformity: Drug concentration in emulgel was measured by UV Spectrophotometer. Oxiconazole content in emulgel was measured by dissolving known quantity of emulgel (1gm) in solvent (100ml methanol) by sonication. Then in a separator funnel, aliquots of methonolic solution of Oxiconazole nitrate (total 100ml) was added to 3ml 0.1 M citric acid solution (pH 2.3). Then 2ml of 0.1% Methyl orange (w/v) in 40% aqueous methanol (v/v) was added. The reaction mixture was extracted by shaking with 10ml of dichloromethane. The organic extract was collected, then absorbance of the resulting solution was measured after suitable dilutions in UV-Visible spectrophotometer at 427 nm against a reagent blank prepared in the same manner without the addition of the drug^22,23.

f) In vitro drug release study:

Franz diffusion cell was used for this study. 200mg of gellified emulsion was evenly applied on to the surface of egg membrane. The egg membrane was placed between the donor and the receptor chamber of diffusion cell. Freshly prepared phosphate buffer solution (pH 6.8) was placed in the receptor chamber which helps to solubilize the drug. A magnetic stirrer is fixed at the receptor chamber. The samples are collected at suitable time interval.

Take each sample in a separator funnel, and then add 3 ml 0.1 M citric acid solution (pH 2.3) mix for a while. Then, 2ml of 0.1% Methyl orange (w/v) in 40% aqueous methanol (v/v) was added. The reaction mixture was extracted by shaking with 10 ml of dichloromethane. Separate the organic phase. Then absorbance of the organic solution was measured in UV Visible spectrophotometer at 427nm against a reagent blank prepared in the same manner without the addition of the drug. The cumulative amount of drug release across the egg membrane was determined as a function of time.

g) Skin irritation test (Patch test): A set of 4 rats was used in the study. A 0.5gm of emulgel formulation was applied on the properly shaven area of skin approximately 1 inch x 1 inch (2.54cm x 2.54cm). The undesirable changes like skin colour, change in skin morphology was checked for a period of 24 hours.

4. RESULTS AND DISCUSSION:

I. Physicochemical Properties:

Table No. 2: Physicochemical properties of Oxiconazole nitrate

S. No	Preformulation test	Results
1.	Description	White in colour
2.	Odour	Odorless
3.	Nature	Amorphous powder
4.	Solubility	Soluble in methanol; sparingly soluble in ethanol, chloroform and acetone; and very slightly soluble in water.
5.	Category	Anti fungal agent
6.	Melting Point	143^°C

II. Standard curve of oxiconazole:

The standard graph was constructed by making the concentrations of 5µg/ml, 10µg/ml, 15µg/ml, 20µg/ml, 25µg/ml and 30µg/ml solutions. The absorbances of solutions were examined under UV-Visible Spectrophotometer at an absorption maximum of 427 nm. The standard graph was drawn by taking the absorbance on y-axis and the concentration on x-axis. The standard calibration curve of Oxiconazole was shown in figure No. 1. Drug concentration and absorbance followed linear relationship. So, the curve obeyed Beer- Lambert’s law and the correlation co-efficient value (R²) was 0.999.

Table No. 3: Standard curve of Oxiconazole

S. No	Concentration (µg/ml)	Absorbance at 427 nm
1.	5	0.118
2.	10	0.235
3.	15	0.348
4.	20	0.471
5.	25	0.587
6.	30	0.696

Figure No. 1: Standard Curve of Oxiconazole

III. Evaluation tests for Oxiconazole emulgel:

Emulgels were prepared according to the formulae specified in the table no. 1 and were evaluated. The evaluation test results and their reports are as follows.

a) Physical Examination:

The prepared Oxiconazole emulgel formulations were white, viscous, creamy preparation with a smooth, homogeneous appearance with good consistency and without any gritty particles.

Table No. 4: Physical examination of emulgel formulations

S.No	Formulation code	Color	Phase separation	Grittiness	Homogenicity	Consistency
1	F1	White	None	-	Excellent	Excellent
2	F2	White	None	-	Excellent	Excellent
3	F3	White	None	-	Excellent	Excellent
4	F4	White	None	-	Excellent	Excellent
5	F5	White	None	-	Excellent	Excellent
6	F6	White	None	-	Excellent	Excellent

b) Measurement of pH:

The pH of the emulgel formulations was in the range of 5.4 to 5.8 and there was no significant change in pH values as a function of time for all formulations which are considered acceptable to avoid the risk of irritation upon application to the skin because adult skin pH is 5.5.

Table No. 5: pH of emulgel formulations

S. No	Formulation code	pH value
1	F1	5.5±0.01
2	F2	5.4±0.02
3	F3	5.8±0.10
4	F4	5.5±0.14
5	F5	5.4±0.12
6	F6	5.6±0.14

(mean ± SD; n=3)

c) Spreadability:

The observations for spreadability of all formulations are shown in the table no. 6. The spreadability of the formulation depends on its viscosity. The greater the viscosity the longer will be the time taken for spreading on the skin.

Table No. 6: Spreadability of emulgel formulations

S. No	Formulation code	Spreadability(cm)
1	F1	6.0±0.1
2	F2	5.8±0.2
3	F3	5.7±0.1
4	F4	5.9±0.05
5	F5	5.7±0.12
6	F6	5.5±0.15

(mean ± SD; n=3)

d) Determination of viscosity:

The measurement of viscosity of the prepared Emulgel was done with a Brookfield Viscometer. The viscosity was measured at 10rpm after 60 seconds. At each speed, the corresponding dial reading was noted. The viscosity of the emulgel was obtained.

Table No. 7: Viscosity of emulgel formulations

S. No	Formulation code	Viscosity (cp)
1	F1	3337±0.13
2	F2	4528±0.15
3	F3	8129±0.19
4	F4	3529±0.12
5	F5	4693±0.10
6	F6	8232±0.12

(mean ± SD; n=3)

e) Drug content:

Drug content was calculated using the following equation, which was obtained by linear regression analysis of calibration curve. The drug content of all emulgel formulation is found within range 92.17 – 98.50%.

Drug content= (Concentration× Dilution factor× Volume taken) × Conversion factor

Table No. 8: Drug content of emulgel formulations

S. No	Formulation code	Drug Content (%)
1	F1	98.5±0.01
2	F2	97.2±0.11
3	F3	94.22±0.15
4	F4	97.65±0.12
5	F5	96.22±0.14
6	F6	92.17±0.01

(mean ± SD; n=3)

f) In vitro drug release studies:

The in vitro diffusion studies of all formulations (F1 to F6) were conducted and the results are shown in Table No. 9. The amount of drug released from different formulations F1, F2, F3, F4, F5 and F6 at the end of 8 hrs were 58.57%, 49.65%, 43.05%, 54.98%, 47.29% and 42.12% respectively.

Figure No. 6: In vitro drug release profile for different formulations from F1 to F6

g) Skin irritation test:

The allergic symptoms like inflammation, redness, irritation, erythema and edema are not appeared on rats up to 24 hr.

5. CONCLUSION:

Oxiconazole emulgel formulations prepared by using polymers like Carbopol 934 and HPMC K4M showed acceptable physical properties, viscosity and drug release. Carbopol 934 based emulgel in its low concentration i.e., F1 proved to be the optimized formulation, since it showed highest drug release i.e., 58.57% in 8 hrs. The release of Oxiconazole from the emulgel was observed as sustained release in a controlled manner. So, emulgel is one of the best topical drug delivery and it is very effective for loading of hydrophobic drugs.

6. ACKNOWLEDGEMENT:

The authors like to acknowledge the Principal and Department of Pharmaceutics, Vijaya Institute of Pharmaceutical Sciences for Women, Vijayawada for providing all requirements and facilities to successfully carry out this research work.

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Received on 17.01.2022 Modified on 20.03.2022

Asian J. Pharm. Tech. 2022; 12(3):232-236.

DOI: 10.52711/2231-5713.2022.00038

TIME (hr)	F1	F2	F3	F4	F5	F6
1	8.05±0.11	7.56±0.14	6.02±0.01	7.92±0.05	6.86±0.12	5.91±0.02
2	15.54±0.01	13.95±0.11	11.87±0.12	14.23±0.12	11.99±0.11	9.25±0.05
3	24.92±0.11	20.57±0.14	15.85±0.14	22.99±0.13	18.24±0.01	13.64±0.05
4	33.25±0.15	25.25±0.15	20.65±0.07	30.93±0.14	23.22±0.10	18.54±0.01
5	42.98±0.02	36.65±0.02	27.87±0.06	39.99±0.02	25.44±0.12	24.29±0.03
6	51.38±0.14	41.24±0.17	34.96±0.05	47.02±0.03	31.55±0.14	30.15±0.05
7	53.11±0.13	45.45±0.13	39.78±0.10	50.85±0.04	37.99±0.01	35.54±0.04
8	58.57±0.11	49.65±0.21	43.05±0.12	54.98±0.02	47.29±0.23	42.12±0.02