INTRODUCTION:

NSAIDs are incorporated in topical formulations that are designed to deliver drugs at appropriate rates to maintain minimum plasma drug levels for therapeutic efficacy by using skin as the port of entry of drugs^1,2,3. One side, the topical applications of the drug offer the potential advantages of delivering the drug directly to the site of action and delivering the drug for extended period of time at the inflammation site that mainly acts at the joint and the related regions. On the other hand, topical delivery system increases the contact time and mean resident time of drug at the applied site leading to an increase in local drug concentration while the pharmacological activity of gel formulations may not change as rapidly as the solution form^1,4.

Emulgels are emulsions, either of the oil in water or water in oil type, which are incorporated into the gels. They have patient acceptability since they possess the advantages of both emulsion and gels such as being thixotropic, greaseless, spreadable, washable, non-staining and compatible with several excipients.

The problem associated with formulations like creams and ointments are greasy, difficult to remove from the skin and cause staining; therefore there is a need to develop emulgel formulations. Therefore, the combined advantages of both emulsions and gels such as being thixotropic, greaseless, spreadable, removable, non staining and compatible with several excipients are achieved by emulgel. Emulsified gels are stable and better vehicles for hydrophobic or water insoluble drugs⁵. Drugs may be soluble in oil core or incorporated into the oil/water interface according to its lipophilicity. Hence drug remains in its solubilized form.

Emulgels are emulsified systems which contain water, that is, most emulgels are oil-in-water (o/w) emulsions. Emulsions are systems which incorporate two immiscible liquids into a dosage form. The two liquids are usually water and oil-based liquids. The emulsification process results in the dispersion of one of the liquids (the dispersed phase) in the other (the continuous phase). The dispersed phase usually exists as discrete globules or droplets. One of the main disadvantages of an emulsion is that there is a large surface area of particles dispersed in the continuous phase. This means that there is a lot of interfacial tension in these formulations which may reduce the stability of the formulation⁶. Production of creams is complicated by the need to include several excipients to promote the stability of the formulation. In addition to these disadvantages, owing to the fact that emulsion contains a significant amount of water, they are susceptible to microbial growth with subsequent stability implications. Hence, either preservative must be incorporated or the emulsion formulation will be required to be manufactured under aseptic conditions^6,7,8. Emulgel contain many components like oily phase in which drug is in the solubilized form, solvents, co-solvents to alter drug solubility, emulsifiers to make stable emulsion and gelling agents to provide the consistency, anti-oxidants and preservatives to provide extended shelf-life and skin permeation enhancers to increase skin permeability. The aim of this work was to develop an emulgel formulation of dexibuprofen, a hydrophobic drug, using Carbopol 940 as gelling agent. The rheological studies, spreading coefficient studies, skin irritation studies, in-vitro release, ex-vivo release studies, anti-inflammatory activity and analgesic activity of the prepared emulgels were also evaluated.

MATERIALS AND METHODS:

Dexibuprofen was obtained as a gift sample from Glochem Industries Limited, Hyderabad, (Andhra Pradesh), India. Carbopol 940 was obtained from Loba chemicals Mumbai. Nylon membrane was procured from Hi media, Mumbai. All other chemicals used were of analytical grade and were used without any further chemical modification.

Preparation of emulgel:

Preparation of emulgel involves two steps:

I. Preparation of o/w emulsion

II. Preparation of emulgel by mixing with the gelling agent.

I. Preparation of O/W emulsion:

The steps involved in the formulation of emulgel included the preparation of emulsion followed by the addition of gelling agent into emulsion to form a semisolid formulation. The oily phase of emulsion was prepared by dissolving span 20 in isopropyl myristate while the aqueous phase was prepared by dissolving Tween 80 in distilled water. Preservative were dissolved in propylene glycol and added to aqueous phase. Both oily phase and aqueous phase were separately heated to 60° to 65°C; then ethanolic solution of dexibuprofen was added to the aqueous phase. The oily phase was added to the aqueous phase in form of thin stream with continuous stirring at a speed of 1500-1600 rpm for 25-30 minutes^8,9,10. The obtained emulsion was evaluated for its physicochemical parameters such as colour, homogeneity, creaming and cracking using 3² factorial design. 3² factorial design approaches by varying two independent variables (X₁ and X₂) at four levels. The compositions of different emulsion formulations are depicted in Table 1.

X₁ = Concentration of emulsifying agents (Levels: 3, 5, and 6%w/w)

X₂= Concentration of inner phase (Levels: 2, 4, and 5%w/w)

At low surfactant concentration both creaming and cracking was observed. As the concentration of surfactant was increased gradually, creaming occurred in the formulation but on shaking a homogenous emulsion was produced. At higher surfactant concentration stable emulsions were obtained. From the observation of 3²factorial design, formulations E-7, E-8, and E-9 were stable in terms of appearance, homogeneity, creaming and cracking. These batches were selected for the preparation of emulgel. The observation of emulsion by 3²factorial design given in Table 2.

Table 1. Composition of emulsion formulations containing Dexibuprofen (%w/w)

Ingredients	E1	E2	E3	E4	E5	E6	E7	E8	E9
Dexibuprofen	7.5	7.5	7.5	7.5	7.5	7.5	7.5	7.5	7.5
Isopropyl myristate	2	4	5	2	4	5	2	4	5
Span 20	1.6	1.6	1.6	4.1	4.1	4.1	4.5	4.5	4.5
Tween 80	1.4	1.4	1.4	0.9	0.9	0.9	1.5	1.5	1.5
Ethyl alcohol	2	2	2	2	2	2	2	2	2
Propylene glycol	5	5	5	5	5	5	5	5	5
Purified water q.s.	100	100	100	100	100	100	100	100	100

Table 2. Observation of emulsion formulations containing Dexibuprofen

Parameters	E1	E2	E3	E4	E5	E6	E7	E8	E9
Colour	White	White	White	White	White	White	White	White	White
Consistency	Liquid	Liquid	Liquid	Liquid	Liquid	Liquid	Liquid	Liquid	Liquid
Creaming	Yes	Yes	Yes	Yes	Yes	Yes	No	No	No
Cracking	Yes	Yes	Yes	No	No	No	No	No	No

Fig 1. Factorial design for emulsion formulations

II. Preparation of emulgel by mixing with the gelling agent.

Carbopol 940 was used as gelling agent for emulgel formulations. Different concentrations range of gelling agent was added to selected emulsion formulations E-7, E-8 and E-9^11,12. The compositions of different emulgel formulations are depicted in Table 3.

Table 3. Composition of different emulgel formulations % w/w

Ingredients	EG-7	EG-8	EG-9
Dexibuprofen	7.5	7.5	7.5
Isopropyl myristate	2	4	5
Span 20	4.5	4.5	4.5
Tween 80	1.5	1.5	1.5
Ethyl alcohol	2	2	2
Propylene glycol	5	5	5
Carbopol 940	1.5	1	1
Purified water q.s.	100	100	100

Evaluation of Emulgels^13,14

Physical examination:

The optimized emulgel formulations were inspected visually for their colour, homogeneity and consistency.

Determination of pH:

The pH of emulgel formulations were determined by digital pH meter. One gram of gel was dissolved in 100 ml of distilled water. The measurement of pH of each formulation was carried out in triplicates.

Viscosity measurement:

Brookfield synchrolectric viscometer model RVT attached with spindle D was used for determination of viscosity. Emulgels were filled in jar and spindle was lowered perpendicularly taking care that spindle do not touch bottom of the jar. The spindle was rotated in the gel at increasing shear rates 0.5, 1, 2.5 and 5rpm. At each speed, the corresponding dial reading was noted. The reverse reading was also noted and average was taken for these two readings. The viscosity of the emulgel was obtained by the multiplication of the dial readings with the factors given in the Brookfield viscometer catalogues.

Spreadability study:

A modified apparatus consisting of two glass slides containing emulgel formulation in between with the lower slide fixed to a wooden plate and the upper one attached to a balance by a hook was used to determine spreadability.

Emulgel EG-8 and E-9 formulated using 1.0 % w/w concentration of Carbopol 940 gave desired properties in terms of appearance, color, homogeneity, and phase separation. Emulgel EG-7 containing 1.5% Carbopol does not having the good consistency, therefore, only EG-8 and EG-9 formulations were selected for further studies.

In-vitro permeation studies:¹⁴

In vitro permeation studies were performed using Franz Diffusion Cell. The capacity of receptor chamber was 20 ml with an effective diffusion area of 3.14 cm². Nylon membrane was used as a diffusion membrane having pore size of 0.2 µm. Receptor chamber containing pH 7.4 phosphate buffer was stirred at 300 rpm and temperature maintained at 37±1°C. 0.5, 1, 2, 3, 4, 5, 6, 7 and 8 hour time intervals, 2 ml samples was withdrawn from the receptor compartment and replaced with an equal volume of fresh buffer. The collected samples were then diluted to fresh buffer. The samples were analyzed by measuring absorbance at 223 nm using UV Spectroscopic method. The cumulative amount of drug released was calculated from the plot of cumulative drug release vs. time. The flux was calculated from the slope of linear portion of the curve. The flux of the developed emulgel was compared with the conventional gel .

Ex-vivo diffusion studies:^15,16,17

To confirm the results of in-vitro diffusion study, ex-vivo studies were conducted on these Emulgel EG-4 and EG-5 using porcine skin^10,13. The skin was equilibrated with the receptor medium before diffusion study until to zero reading was obtained. Sampling was done in half an hour interval from the receptor compartment and analyzed using UV spectrophotometer to ensure that receptor medium did not have any residue. The phosphate buffer pH 7.4 solution was replaced after 2 hours. The aliquot did not show any absorbance indicating complete stabilization of the skin.

After stabilization of the porcine skin, diffusion studies were carried out. The receptor compartment was filled with phosphate buffer pH 7.4 solution which was stirred at 300 rpm using magnetic stirrer to maintain the sink conditions. The donor compartment facing porcine skin was loaded with 500 mg of the optimized emulgel. At specified intervals of time i.e. 0.5, 1, 2, 3, 4, 5, 6 and 24 hours, two ml aliquots were withdrawn from receptor compartment through the sampling port and it was replaced with the same amount of freshly prepared phosphate buffer pH 7.4 each time. Aliquots were analyzed by UV Spectrophotometer at 223 nm using phosphate buffer pH 7.4 as blank.

Skin irritation studies:^{18, 19}

Draize patch test was performed on albino rabbit as the animal model¹¹. The optimized formulation was applied on the patch of preshaved (both intact and abraded) skin. The resulting reactions such as erythema and edema were scored after 24 and 72 h.

Stability studies:

The prepared emulgels were packed in aluminum collapsible tubes (5 g) and subjected to stability studies at 5 ^oC, 25 ^oC/ 60% RH, 30 ^oC/65% RH, and 40 ^oC/75% RH for a period of 3 months. Samples were withdrawn at 15-day time intervals and evaluated for physical appearance, pH, rheological properties and drug content²⁰.

Pharmacodynamic study:

In pharmacodynamic studies was to demonstrate the in- vivo anti-inflammatory activity and analgesic activity of the optimized formulations in animals and compare it with that of control. The protocol of in vivo studies was approved by the Animals Ethics Committee of C. U. Shah College of Pharmacy. The carrageenan-induced rat paw edema model and Hot Plate Test Methods were used for in-vivo studies ²¹.

Anti-inflammatory activity:

This method was used to measure the anti-inflammatory activity by inducing rat paw edema by carrageenan.

Experimental animals:

Wistar rats (180 – 200 g) were used for the study. All the animals were kept under standard conditions of light and dark cycle with food and the animals were allowed to acclimatize for one week before the experiments. The overnight fasted animals were divided into following three groups of four rats each. Saline solution was used as control.

Group I Control

Group II EG-4 and EG-5

Anti-inflammatory activity:

In order to measure paw volume; animals were marked with permanent marker at ankle of their left hind paw to define the area of paw to be monitored. Paw edema was induced by injecting 100 µl of 1% solution of carrageenan (w/v) in normal saline into the plantar surface of the left hind paw. Half an hour after the test formulation (500 mg) was applied on the dorsal area. The paw volumes were measured with a plethysmometer at 0 (before administration of carrageenan) and 1, 2, 3, 4 and 24 hours after carrageenan administration, and the change in paw volume in control and drug treated animals was calculated. The % increase in edema at each point for test formulation in comparison to control group was also calculated. The anti- inflammatory activity was expressed as % inhibition of paw edema.

% Edema = b-a × 100/a

Where,

a = Paw volume measured before producing edema.

b = Paw volume measured at predetermined intervals after producing edema and application of the formulation.

Analgesic activity:

This method was used to measure the anti nociceptive effect of test formulations to an acute thermal stimulus.

Experimental animals:

Swiss mice were used as animal models. The animals were divided into following three groups of four mice each.

Group I Control

Group II Optimized formulation (EG-4 and EG-5)

Analgesic activity:

Acute thermal stimuli study was carried out in mice using hot plate analgesiometer. This study was carried out for 1, 2, 3, and 4 hrs. Test formulation and marketed formulation was applied on dorsal surface area of mice. Latency to the heat stimulus was measured by the number of times the animal licks one of its paws in cut off time of 15 seconds. The analgesic activity was measured as % maximal possible effects.

% MPE = b-a × 100

Where,

% MPE= maximal possible effects

b =Latency to respond to thermal stimulus by control.

a = Latency to respond to thermal stimulus by test formulations.

RESULTS AND DISCUSSION:

Physical appearance:

Emulgel formulations were white viscous creamy preparation with a smooth homogeneous texture and glossy appearance. Results have been discussed in Table 2.

pH determination:

The pH of all formulation is kept between pH-5.5 to 6.0. The pH is a main parameter here since above pH-7 the formulation colour changes to pink colour and below pH-5 the drug solubility was less and also to avoid skin irritation. The results are given in Table 2.

Viscosity and spreadability measurement:

Viscosity of the all the optimized formulation were found to be good and having excellent spreadability. Results are predicted in Table 2.

Table 4. Physicochemical evaluation of optimized emulgel formulations containing Dexibuprofen.

Parameters	EG-7	EG-8	EG-9
Appearance	Semisolid consistency	Semisolid consistency	Semisolid consistency
Colour	White	White	White
Homogeneity	Homogeneous	Homogeneous	Non-homogeneous
pH	5.5	5.5	6.0
Apparent Viscosity (cps)	9543	9010	8360
Spreadability (gm cm sec^-2)	55.23	65.45	64.21

In-vitro permeation studies:

The in-vitro release profiles of Dexibuprofen from optimized emulgel formulations are represented in figure 1. In general, it can be observed from figure that the better release of the drug from all emulgel formulation. From results of in vitro diffusion studies using Franz diffusion cell, it can be concluded that EG-5 had better flux 33.55±0.23 than EG-4 28.56±0.43 emulgel formulations. This is may be because of higher concentration of surfactant and oil in EG-.

Fig 2. In-vitro released data for emulgel formulations

In-vivo release studies:

The study showed the flux of the drugs from optimized emulgel formulation EG-8 and EG-9 were 12.45±0.56 and 9.93±0.32, respectively in 240 min. The results are show in Fig. 2.

Fig 3. Ex-vivo release data for emulgel formulations

Skin irritation studies:

No erythema or edema occurred during primary skin irritation studies on the rabbits hence formulation was found to be safe and non irritant for topical application. The developed formulation released the drug over a prolonged period of time hence would be more suitable for once or twice a day application.

Stability studies:

The optimized formulation was kept under different storage conditions and the optimized formulation was found to be stable in terms of physicochemical characteristics as well as drugs release behavior.

Anti-inflammatory studies:

Anti-inflammatory studies in rats by carrageenan-induced rat paw edema method. The differences in percentage of edema at 1, 2, 3, 4, and 24 hrs was observed. The optimized gel formulation EG-9 showed improved anti- inflammatory activity as compared to control group.

Analgesic activity:

Acute thermal stimuli study was carried out in mice using hot plate analgesiometer. Significant increase in percentage of MPE at 1, 2, 3, and 4 hours were observed. The test formulations showed improved analgesic activity as compared to marketed formulation.

CONCLUSION:

Topical emulgels of Dexibuprofen were formulated and subjected to physicochemical studies, in- vitro release studies and ex-vivo release studies through rat skin. From the in-vitro studies and ex-vivo formulation EG-9 showed maximum flux of 33.55±0.23 µg/cm²/hr and 12.45±0.56 µg/cm²/hr in 8hr respectively. Carrageenan induced rat paw edema and hot plate tests revealed anti-inflammatory and analgesic activity. The formulations EG-9 was comparable with control formulation.

From the results obtained in the present work, it can be concluded that the emulgel formulations can be an innovative and promising approach for the topical delivery of Dexibuprofen for the treatment of inflammation and pain.

ACKNOWLEDGEMENTS:

Authors are Thankful to Principal, Manoharbhai Patel Institute of Pharmacy (B-Pharm), Gondia, supporting this research work.

REFERENCES:

1. Bhaskaran S, Harsha NS. Effect of permeation enhancers and iontophoresis on permeation of atenolol from transdermal gels. Ind J Pharm Sci. 2000; 6:424-426.

2. Brown MB, Martin GP, Jones SA, Akomeah FK., Dermal and transdermal drug delivery systems: current and future prospects. J. European Acad. Dermatol. Venerology, 2006; 13:175-187.

3. Giannakou SA, Dallas PP, Rekkas DM, Choulis NH. , Development and in vitro evaluation of nitrendipine transdermal formulations using experimental design. Int J Pharm Tech. 1995; 125:7-15.

4. Kumar R, Philip A. , Modified Transdermal Technologies: Breaking the Barriers of Drug Permeation via the Skin. Trop J Pharm Res. 2007; 6:633-644.

5. J. Hadgraft, C. Valenta, pH, pKa and dermal delivery, Int. J. Pharm, 2000; 243-247.

6. Emulsions and Creams. In: Dispensing for Pharmaceutical Students, 12th Edition, Ed Carter S J, Kent, England: Pitman Medical, 1975; 120-166.

7. Eswaraiah S., Swetha K., Lohita M., P. Jaya Preethi, B. Priyanka, Kiran Kumar Reddy. Emulgel: Review on Novel Approach to Topical Drug Delivery. Asian J. Pharm. Res. 4(1): Jan.-Mar. 2014; 04-11.

8. Winfield A J. External Preparatoins. 3rd Edition, Eds Winfield A J, Richards R M E, New York: Churchill Livingstone, 2004; 206 – 217.

9. Anuradha A Sawant, S.K. Mohite. Formulation and Evaluation of Itraconazole Emulgel for Topical Drug Delivery. Asian J. Pharm. Tech. 2015; Vol. 5: Issue 2, 91-96.

10. Mayuresh. R. Redkar, Priyajit S Hasabe, Suraj. T. Jadhav, Pankaj S Mane, Deepak J Kare. Review on Optimization base Emulgel Formulation. Asian J. Pharm. Tech. 2019; 9(3):228-237.

11. Kshama R. Phutane, Suvidha S. Patil, Rahul S. Adnaik, Manoj M. Nitalikar, Shrinivas K. Mohite, Chandrakant S. Magdum. Design and Development of Allopurinol Emulgel. Research J. Pharm. and Tech. 7(7): July 2014, 733-736.

12. Pratiksha V. Shrikhande. Formulation and Evaluation of Polyherbal Topical Anti-Inflammatory Emulgel. Research J. Pharm. and Tech. 6(1): Jan. 2013; 118-122.

13. Jayprakash. S. Suryawanshi, Shivaji. P. Gawade. Enhanced anti-arthritic effect of mustard oil in Nanoemulgel Formulation: A comparative clinical study. Research J. Pharm. and Tech. 2020; 13(8): 3738-3744.

14. Kumar Bandhu Lathiyare, Vishal Jain. Development and characterization of karanj oil based proniosomal gel for topical delivery. Research J. Pharm. and Tech. 7(9): Sept. 2014, 1052-1059.

15. Deepika John, R. Narayana Charyulu, Ravi G. S, Jobin Jose. Nanosponge Based Hydrogels of Etodolac for Topical Delivery. Research J. Pharm. and Tech. 2020; 13(8):3887-3892.

16. Simon G. A., Maibac Simon G. A., Maibach H. I. The pig as an experimental animal model of percutaneous permeation in man : qualitative and quantitative observations- an overview. Skin Pharmacol. Appl. Skin Physio.,2000; 13, 229-234.

17. Primary Skin Irritation Test in the Rabbit of Water Jel Burn Dressing. [Online]. 2007. [Cited 2007 September 13]. Available from: URL: http://www.waterjel.com/public/SkinIrritationTest.pdf

18. ICH Harmonized Tripartite Guideline Stability Testing of New Drug Substances and Products Q1A (R2). 2003.

19. K.G. Malviya, U.D. Shivhare, Preeti Srivastav, S.C. Shivhare. Evaluation of Analgesic potential of Cyathocline lyrata Cass Plant in Rats by using Tail Flick and Hot Plate Method. Asian J. Pharm. Res. 3(2): April- June 2013; 82-85.

20. H. Gerhard Vogel, Analgesic, Anti-inflammatory and Antipyretic activity. Drug Discovery and Evaluation. 2002; 670-773.

21. N. Kasliwal, D. Derle, J. Negi, J. Gohil. Effect of permeation enhancers on the release and permeation kinetics of meloxicam gel formulations through rat skin. Asian J. Pharm. Sci. 2008; 3 (5): 193–199.

Received on 10.11.2020 Modified on 27.02.2021

Research J. Pharm.and Tech 2022; 15(2):745-750.

DOI: 10.52711/0974-360X.2022.00124