1. INTRODUCTION:

Drugs can be administered by numerous routes to human body namely oral, sublingual, rectal, parental etc. When drug administration through other routes fails or skin infections occur, transdermal delivery system could be employed. Large numbers of dermal products are existing for skin as liquids, powders etc. however the most accepted products are semisolid preparation. Among the semisolid preparations, the transparent gels are utilized both in cosmetics and in pharmaceutical preparations. Gels were prepared by entrapment of large amounts of aqueous or hydroalcoholic liquid in a network of colloidal solid particles. Gel formulations normally demonstrate improved drug release than ointments and creams.

A main drawback is in the release of hydrophobic drugs. Such types of troubles were overcome by emulgel preparations. When gels and emulsion were mixed jointly emulgel is formed. Water phase containing gelling agent would convert an emulsion into an emulgel. Oil in water system was utilized for encapsulating lipophilic drugs whereas water in oil system was utilized for hydrophilic drug. Emulgels could be washed away without difficulty whenever needed and as well shows elegant properties. It in addition illustrates good penetration through the skin¹. Emulgels with properties such as being thixotropic, greaseless, easily spreadable, easily removable, emollient, non-staining, water soluble, longer shelf life, biofriendly, transparent and pleasing appearance were used for dermatological purposes. Drug molecules can penetrate into the skin by three routes: through intact stratum corneum, through sweat ducts, or through sebaceous follicle. The surface of the stratum corneum presents more than 99% of the total skin surface accessible for percutaneous drug absorption. Passage through this outermost layer was the rate limiting step for percutaneous absorption. The key steps involved in percutaneous absorption consist of the establishment of a concentration gradient, release of drug from the vehicle (partition coefficient), and drug diffusion across the layers of the skin (diffusion coefficient).

1.1 Advantages of emulgel:

· Evading of first pass metabolism.

· Prevention of gastrointestinal incompatibility².

· Avoidance of the risks and inconveniences of intravenous therapy and of varied conditions of absorption, like pH changes, presence of enzymes, gastric emptying time.

· More selective to a specific site.

· Get better patient compliance.

· No intensive sonication:

Sonication was needed for the production of vesicular molecules which might result in drug degradation and leakage. Although this difficulty is not seen during the production of emulgels, as no sonication was needed.

· Suitability for self-medication³.

· Controlled release: Drugs which have shorter half life, emulgels could be employed to extend the effect of drugs.

· Providing utilization of drug with short biological half-life as well as narrow therapeutic window.

· Emulgel preparation was simple plus short steps which enhances the feasibility of the production. There were no specialized instruments required for the manufacture of emulgels ⁴. Materials which were used for the preparation of emulgel are available with no trouble and cheaper. Therefore, reduces the production cost of emulgels.

· In gel base, hydrophobic drugs cannot be included directly since solubility act as a barrier, furthermore problem arises during the release of the drug. Hydrophobic drugs could be incorporated in to the oily phase of Emulgel and subsequently oily globules are dispersed in aqueous phase which consequences in o/w emulsion, afterward this emulsion can be mixed into gel base. This might be providing enhanced stability with release of drug than simply incorporating drugs into gel base.

· Better stability: Other topical preparations were comparatively less stable than emulgel. Like powder show hygroscopicity, creams shows breaking or phase inversion and ointment shows rancidity owing to oily base⁵.

1.2 Disadvantages of emulgel:

· Skin irritation on contact dermatitis.

· Bubbles formed during emulgel formulation.

· Chance of allergenic reactions⁶.

· Drugs with large particle size (>400 daltons) are not easily absorb or cross through the skin barrier.

· Poor permeability of some drugs through the skin.

1.3 Ideal properties of drug candidate to formulate as emulgel:

· Drug dose should be low i.e. less than 10 mg.

· Molecular weight of drug should be 400 Dalton or less.

· Drugs with low half life could be formulated as emulgel.

· Low oral bioavailability and therapeutic index drugs could be formulated as emulgel.

· Drug should be non- irritating and non-sensitizing⁷.

1.4 Rationale of emulgel as a topical drug delivery system:

There are various medicated products that are applied to the skin or mucous membrane that either augment or restore a fundamental function of skin or pharmacologically alter an action in the underlined tissues. Such products are called as topical or dermatological products. Extensively used topical products like ointments, creams, lotions have several disadvantages. They are extremely gluey causing discomfort to the patient when applied. Moreover they too have lesser spreading coefficient as well as require to apply with rubbing, and they reveal the problem of stability too¹⁸.

Owing to all these factors within the major group of semisolid preparations, the use of transparent gels has expanded both in cosmetics and in pharmaceutical preparations. A gel is colloid that is usually 99% wt. liquid, which is immobilized by surface tension between it and a macromolecular network of fibers built from a small amount of a gelating substance present. In spite of many advantages of gels a major limitation is in the delivery of hydrophobic drugs. Hence to overcome this constraint an emulsion based approach is being utilized so that even a hydrophobic therapeutic moiety could be effectively included and delivered through gels¹⁹.

1.5 Physiology of skin:

The majority of the topical preparations are meant to be applied to the skin. Therefore, basic knowledge of the skin and its physiology function are very essential for designing topical delivery systems. The skin of an average adult body covers a surface area approximately 2m² and receives about one third of the blood circulating through the body. An average human skin surface is known to contain, on the average 40-70 hair follicles and 200-300 sweat ducts on every square centimeter of the skin. The pH of the skin varies from 4 to 5.6. Sweat and fatty acid secreted from sebum influence the pH of the skin surface. The skin can be considered to have four different layers of tissue as shown in figure 1.

1. Non-viable epidermis

2. Viable epidermis

3. Viable dermis

4. Subcutaneous connective tissue

Non-viable epidermis:

Stratum corneum is the outer most layer of skin, which is the real physical barrier to most substances that comes in contact with the skin. The stratum corneum is 10 to 20 cell layer thick over most of the body. Each cell is a flat, plate like structure 34-44μm long, 25-36 μm wide, 0.5 to 0.20μm thick with surface area of 750 to 1200μm stocked up to each other in brick like fashion. Stratum corneum have lipid (5-15%) including phospholipids, glycosphingo lipid, cholesterol sulfate and neutral lipid, protein (75-85%) which is chiefly keratin²⁰.

Viable epidermis:

This layer of the skin resides between the stratum corneum and the dermis and had a thickness in the range of 50-100μm. The structures of the cells in the viable epidermis are physiochemically alike to other living tissues. Cells are held together by tonofibrils. The density of this region is not greatly different than water. The water content is about 90%.

Dermis:

Just underneath the viable epidermis is the dermis. It is a structural fibrin and very few cells are like it can be found histological in normal tissue. Dermis thickness ranges from 2000 to 3000μm and consists of a matrix of loose connective tissue composed of fibrous protein embedded in an amphorphose ground substance. The subcutaneous tissue or hypodermis is not really considered a true part of the structured connective tissue which is composed of loose textured, white, fibrous connective tissue having blood and lymph vessels, secretary pores of the sweat gland and cutaneous nerves. The majority investigators consider drug permeating through the skin go into the circulatory system prior to reaching the hypodermis, even though the fatty tissue could serve up as a depot of the drug ²¹.

Figure 1: Structure of skin

2. BASIC COMPONENTS OF EMULGEL:

A. Aqueous material:

This forms the aqueous phase of the emulsion. Usually used agents are water, alcohols.

B. Oils:

These agents form the oily phase of the emulsion. The oil phase has huge significance in the formulation of emulsion /microemulsion/ nanoemulsion as physicochemical properties of oil (e.g., molecular volume, polarity, and viscosity) notably govern the spontaneity of the emulsification /micro- emulsification / nano emulsification process, the droplet size of the respective emulsion, drug solubility. Typically, the oil, which has the maximum solubilizing potential for the chosen drug candidate, is favored as an oily phase for the formulation of emulsion/ microemulsion/nanoemulsion. This helps to accomplish the maximal drug loading. Hence, the selection of the oily phase is often a compromise between its tendency to solubilize the drug and its capability to make easy the formation of the respective emulsion with desired characteristics ²². Mineral oils, either alone or combined with soft or hard paraffin, are employed for externally applied emulsion and as well used as a vehicle. Oil phases which are utilized in development of emulgel are balsam oil, birch oil, castor oil, isopropyl myristate, myrrh oil, rose hip oil, wheat germ oil.

Table 1: Quantity of oils used in gel, emulgel and emulsion

Chemical	Quantity	Dosage form
Light Liquid Paraffin	7.5%	Emulsion and Emulgel
Isopropyl myristate	7-7.5%	Emulsion
Isopropyl stearate	7-7.5%	Emulsion
Isopropyl palmitate	7-7.5%	Emulsion
Propylene glycol	3.5%	Gel

C. Emulsifiers:

Emulsifying agents are employed both to advance emulsification at the time of manufacture and to control stability during a shelf life. E.g. Polyethylene glycol 40 stearate, Sorbitan mono-oleate (Span80), Stearic acid and Sodium stearate, Polyoxyethylene sorbitan monooleate (Tween 80). Surfactants having HLB values more than 8 such as the nonionic surfactant (spans, tweens) are utilized in the formulation of o/w emulsions while mineral oils such as liquid paraffin have HLB value less than 8 and hence are used in the formulation of water in oil emulsions. In comparison to the individual system of span or tween, mixtures of span 20 and tween 20 consequences greater stability of the emulsion²³.

D. Gelling Agent:

Gelling agents are used to forming gel base which by incorporating emulsion to form emulgel. These are also known as thickening agents which expand the consistency of any dosage form by swelling in the aqueous phase and forming gelly like structure. Inclusion of gelling agent to a system makes it thixotropic. e.g. carbopol 934, carbopol 940.

HPMC based Emulgel was found to be better than carbopol based Emulgel since it showed better drug release rate. Sodium carboxy methyl cellulose based Emulgel was appropriate for vaginal application since it showed high mucoadhesivity which amplified drug residence time and as well best in-vitro and in-vivo performance. HEC based Emulgel had showed low mucoadhesion however good drug release profiles and rheological characteristics. Pemulen based Emulgel was intended for buccal administration ²⁴.

Table 2: Quantity of gelling agents used in emulgel and gel

Gelling agents	Quantity	Dosage form
Carbopol-934	1 %	Emulgel
Carbopol-940	1 %	Emulgel
HPMC-2910	2.5 %	Emulgel
HPMC	3.5 %	Gel
Sodium CMC	1 %	Gel

E. Permeation Enhancers:

They are used to progress the absorption of drugs by disrupting the skin barrier, fluidize the lipid channels between corneocytes, altering the partitioning of the drug into skin structures. Ideally, these materials should be pharmacologically inert, nonirritating, nontoxic, and compatible with the excipients and drugs, colorless, odorless, tasteless, and inexpensive and have good solvent properties. The enhancer should not guide to the loss of body fluids, electrolytes, and other endogenous materials, and skin on its removal should immediately regain its barrier properties²⁵. Commonly used penetration enhancers are oleic acid, lecithin, urea, clove oil, menthol etc.

Properties of penetration enhancers:

· They should be non-toxic, non-irritating and non- allergenic.

· They would ideally work rapidly, and the activity and duration of effect should be both predictable and reproducible.

· They should have no pharmacological activity within the body i.e. should not bind to receptor sites.

· The penetration enhancers should work unidirectional i.e. should allow therapeutic agents into the body whilst preventing the loss of endogenous material from the body.

· The penetration enhancers should be appropriate for formulation into diverse topical preparations, thus should be compatible with both excipients and drugs.

· They should be cosmetically acceptable with an appropriate skin feel.

Table 3: Quantity of penetration enhancers used in emulgel

Penetration enhancer	Quantity	Dosage form
Oleic acid	1 %	Emulgel
Lecithine	5 %	Gel
Urea	10 %	Gel
Isopropyl myristate	5 %	Gel
Linoleic acid	5 %	Gel
Clove oil	8 %	Emulgel
Menthol	5 %	Emulgel

3. METHOD OF PREPARATION:

The gel is prepared by mixing carbopol 934 in purified water and stirring at a moderate speed and carbopol 940 in purified water with stirring. Then pH is adjusted to 6 to 6.5 using TEA. The oil phase contains span 20 in light liquid paraffin and aqueous phase prepared by tween 20 in purified water. Methyl and Propyl paraben are dissolved in propylene glycol whereas drug is dissolved in ethanol and both solutions are mixed with the aqueous phase. Both the oily and aqueous phases are separately heated to 70°- 80°C; then the oily phase is added to the aqueous phase with continuous stirring until cooled to room temperature. Then glutaraldehyde was added during of mixing of gel and emulsion in 1:1 proportion so as to obtain the emulgel²⁶.

Steps for preparing emulgel:

Step 1: Formulation of Emulsion either O/W or W/O.

Step 2: Formulation of gel base.

Step 3: Incorporation of emulsion into gel base with continuous stirring.

Figure 2: Flow chart of Emulgel formulation

4. CHARACTERIZATION OF EMULGELS:

A. Physical appearance: The prepared emulgel is inspected for the colour, homogeneity, consistency.

B. pH: The pH values of 1% aqueous solutions of the prepared gels were measured by a digital pH meter. Electrodes were completely dipped into the semisolid formulations and pH was noted²⁶.

C. Swelling Index: For determination of swelling index of formulated emulgel following procedure adopted, 1 gm of the gel is taken on porous aluminum foil and then placed separately in a beaker of 50ml containing 10ml 0.1 N NaOH. Then samples were taken from beakers at different time points and put it on a dry place for some time after it reweighed. Swelling index is calculated as follows:

Swelling Index (SW) % = [(Wt – Wo)/ Wo] × 100

Where,

Wo = Initial weight of emulgel at zero time

Wt = Weight of swollen emulgel after time t

SW% = Percent swelling Index

D. Spreadability:

Spreadability of emulgel is measured in terms of diameter of emulgel circle produced when emulgel is placed between two glass plates of definite weight. A weighed quantity (350mg) of emulgel is taken on one glass plate and another glass plate is dropped from a distance of 5cm. The diameter of the circle of spread emulgel is measured²⁶.

E. Rheological Studies:

Viscosity of emulgel is determined at 25°C using a cone and plate viscometer with spindle 52 and connected to a thermostatically controlled circulating water bath²⁷.

F. Drug Content Determination:

Emulgel is mixed in a suitable solvent. Filter it to obtain clear solution. Determine its absorbance using UV spectrophotometer. From the standard equation by putting the absorbance value concentration and drug content can be obtained.

Drug Content = (Concentration × Dilution Factor × Volume taken) × Conversion Factor.

G. Extrudability study:

It is calculated by the force required to extrude the emulgel from the tube. The method applied for determination of applied shear in the region of the rheogram corresponding to a shear rate exceeding the yield value and exhibiting consequent plug flow. In this study emulgel extruded from lacquered aluminum collapsible tube on application of weight in grams required to extrude at least 0.5cm ribbon of emulgel in 10 seconds. For better extrudability, more quantity is extruded^[27]. For the measurement of extrudability, it is done in triplicate and the average values are calculated. The extrudability is then calculated by using the following formula:

Extrudability = weight applied to extrude emulgel from tube (in gm) / Area (in cm²)

H. Skin Irritation Test (Patch Test):

The preparation is applied on the properly shaven skin of rat and its adverse effect like change in colour, change in skin morphology should be checked up to 24 hours. The total set of 8 rats can be used of the study. If no irritation occurs the test is passed. If the skin irritation symptom occurs in more than 2 rats the study should be repeated²⁸.

I. In-vitro Release Study:

Franz diffusion cell is used for the study. Emulgel is applied on the surface of egg membrane is clamped between the donor and the receptor chamber of diffusion cell. The receptor chamber contains freshly prepared PBS (pH 5.5) solution to solubilize the drug. The receptor chamber is stirred using magnetic stirrer. The samples (1.0 ml aliquots) are collected at different time interval and analyzed for drug content by UV-visible spectrophotometer after appropriate dilutions ²⁹. Drug release is based on a function of time.

J. Ex–vivo evaluation:

Ex –vivo release study is conducted using preserved or fresh chicken skin. Then skin is allowed to hydrate for 1 h before being mounted on the Franz diffusion cell with the stratum corneum (SC) facing the donor compartment. The gel sample is applied on the skin and then fixed in between donor and receptor compartment of Franz diffusion cell. The receptor compartment contains phosphate buffer of pH 7.4. The temperature of the medium is thermostatically controlled at 37±10ºC by surrounding water jacket and the medium is stirred with bar magnet using magnetic stirrer ³⁰. Aliquots, withdrawn at predetermined intervals of time, are spectrophotometrically estimated at maximum wavelength of drug against their respective blank formulation treated in the same manner.

K. Kinetics Modeling:

Data obtained from ex-vivo permeation studies were fitted into zero order, first order, Higuchi, and mathematical models for evaluation of drug release kinetics. The model for best fit was predicted from the value of R². For an ideal fit, value of R² i.e. higher, the value of R² best was the model fitted. Hence, the model which gives the R²value nearest to 1 describes the best order of drug release ³¹.

L. Accelerated stability studies of Emulgel:

Stability studies are carried out as per ICH guidelines. The formulations are stored for 3 months in stability chamber at 37±2°C, 45 ±2°C and 60 ± 2°C. It is then analyzed for two weeks with UV‐Visible spectrophotometer for drug content. Also, the change in pH is checked for determination of stability ³².

5. MARKETED EMULGEL FORMULATIONS:

Emulgels are commercially obtainable in market. Voltaren Emulgel is a topical analgesic emulgel that offers relief in shoulder pain, back pain and decreases swelling. Voltaren Emulgel is non-greasy, white pleasant-smelling gel which is accessible in a 100g tube having a active ingredient diclofenac sodium 1% w/w (as diclofenac diethylamine). One more emulgel is Diclomax Emulgel which is employed in treatment inflammation of the tendons, ligaments, muscles and joint and manufactured by Torrent Pharma. Miconaz H emulgel which is manufactured by medical union pharmaceuticals having active ingredient miconazole nitrate and hydrocortisone posses bactericidal, fungicidal, anti-inflammatory and antipruriginous properties³³.

Table 4: Marketed Emulgel Formulations

Marketed Formulation	API	Manufacturer	Use
Voltarol 1.16% emulgel	Diclofenac sodium	Novartis	Anti inflammatory
Diclomax Emulgel	Diclofenac sodium	Torent pharma	Anti inflammatory
Miconaz-H-emulgel	Miconazole nitrate, Hydrocortisone	Medical union Pharmaceuticals	Topical corticosteroid and antifungal

6. CONCLUSION:

In the upcoming years, topical drug delivery would be used widely to impart better patient compliance. As the emulgel is the current technique for the topical drug delivery it is better appropriate for hydrophobic drugs and obviously it is very good technique for drug delivery of combination of both hydrophilic and hydrophobic drugs. Since it is also capable in enhancing spreadability, adhesion, viscosity and extrusion, they will become a well-liked drug delivery system. Furthermore, they would become a solution for loading hydrophobic drug in a water soluble gel base.

7. REFERENCES:

1. Davinder Kumar, Jasbir Singh, Mamta Antil and Virender Kumar. Emulgel-novel topical drug delivery system–a comprehensive review. International Journal of Pharmaceutical Sciences and Research 2016; 7(12): 4733 -4742.

2. Sanjay K Jain, Pawan Bajapi, Shailendra K Modi, Prashant Gupta. A Review on Emulgel, as a Novel Trend in Topical Drug Delivery System. Recent Trends in Pharmaceutical Sciences and Research 2019; 1(2): 30 - 39.

3. Begum S. Gousia, Madhusudan Chetty C., Voleti Vijay Kumar, Pavithra B, Akhila B, Gayathri C, Ruksar S and Sravani T. A Review on Emulgels-A Novel Approach for Topical Drug Delivery. Asian Journal of Pharmaceutical Research and Development 2019; 7(2): 70 - 77.

4. Jaise Thomas, S Kuppuswamy, Anwara Aliyar Sahib, Ashinaa Benedict, Eby George. A Review on Emulgel as a Current Trend in Topical Drug Delivery System. International Journal of Pharmacy and Pharmaceutical Research 2017; 9(3): 273 - 281.

5. Shailaja Pant, Ashutosh Badola, Sweta Baluni and Warsha Pant. A review on emulgel novel approach for topical drug delivery system. World Journal of Pharmacy and Pharmaceutical Sciences 2015; 4(10): 1728 - 1743.

6. Sunil Kumar Yadav, Manoj Kumar Mishra, Anupamaa Tiwari, Ashutosh Shukla. Emulgel: A new approach for enhanced topical drug delivery. International Journal of Current Pharmaceutical Research 2017; 9(1): 15 – 19.

7. Devi Suman, Sangeeta and Kumari Beena. Emugel for topical drug delivery: A novel approach. GSC Biological and Pharmaceutical Sciences 2020; 11(03): 104 - 114.

8. Prajakta Kegade, Rutuja Sawant, Shreya Parkar and Akshay Gade. Emulgel: In treatment of periodontitis. World Journal of Advance Healthcare Research 2020; 4(5): 71 – 77.

9. Hyma.P, Noor Jahan, Raheemunissa, Sreelekha and Babu K. Emulgel: A Review. International Journal of Pharmaceutical Archive 2014; 3(3): 1 – 11.

10. R. P. Singh, S. Parpani, R. Narke, R. Chavan. Emulgel: A recent approach for topical drug delivery system. Asian Journal of Pharmaceutical Research and Development 2014; 2(2): 112-123.

11. Sonam Vats, CharuSaxena, TS Easwari, VK Shukla. Emulsion Based Gel Technique: Novel Approach for Enhancing Topical Drug Delivery of Hydrophobic Drugs. International Journal for Pharmaceutical Research Scholars (IJPRS) 2014; 3(2): 649 – 660.

12. Khullar, R., Saini, S., Sethi, N., & Rana, A. C. Emulgel a surrogate approach for topically used hydrophobic drugs. Int. J. Pharm. Biol. Sci., 2011; 117-128.

13. Wani RR, Patil MP, Dhurjad P, Chaudhari CA, Kshirsagar SJ. Microemulsion Based Gel: A Novel Approach in Delivery of Hydrophobic Drugs. IJPRS 2015; 4(2): 397 – 410.

14. Jain A, Gautam SP, Gupta Y., Development and characterization of ketoconazole emulged for topical drug Delivery. Der Pharmacia Sinica 2010; 1(3): 221-231.

15. Kaushal R. Sabu, Ganesh D. Basarkar. Formulation, Development and In-vitro Evaluation of Terbinafine Hydrochloride Emulgel for Topical Fungal Infection. Int. J. Pharm. Sci. Rev. Res., 2013; 21(2): 168-173.

16. Kalpesh Chhotalal Ashara, Jalpa S. Paun, Moinuddin M. Soniwala, Jayant R. Chavada, Nitin Merubhai Mori. Microemulsion based emulgel: a novel topical drug delivery system, Asian Pac J Trop Dis 2014; 4(suppl 1): S27-S32.

17. Rachit K., Saini S., Seth N., & Rana A. Emulgels – a surrogate approach for topical use hydrophobic drugs. International Journal of Pharmacy and Biological Sciences 2011; 1(3): 117 - 128.

18. Mohamed S. D. Optimization of Chlorphenesin Emulgel Formulation. American Association of Pharmaceutical Scientists 2004; 6(3): 1 - 7.

19. Anu Hardenia, Sonali Jayronia and Sanjay Jain: Emulgel: An Emergent Tool In Topical Drug Delivery. Ijpsr 2014; 5(5): 1653 - 1660.

20. Gaur PK, Mishra S, Purohit S and Dave K. Transdermal Drug Delivery System: A Review. Asian Journal of Pharmaceutical and Clinical Research 2009; 2: 14 - 20.

21. Subramanian N, Ghosal SK, Moulik SP. Enhanced in vitro percutaneous absorption and in vivo anti-inflammatory effect of a selective cyclooxygenase inhibitor using microemulsion. Drug development and industrial pharmacy 2005; 31(4-5): 405 - 416.

22. Kanikkannan N, Kandimalla K, Lamba SS, Singh M. Structure activity relationship of chemical penetration enhancers in transdermal drug delivery. Current medicinal chemistry 2000; 7(6): 593 - 608.

23. Panwar A, Upadhyay N, Bairagi M, Gujar S, Darwhekar G, Jain D. Emulgel: a review. Asian J Pharm Life Sci. 2011; 1(3): 2231:4423.

24. Pathan IB, Setty CM. Chemical penetration enhancers for transdermal drug delivery systems. Tropical Journal of Pharmaceutical Research 2009; 8(2): 173 - 179.

25. Jain A, Deveda P, Vyas N, Chauhan J, Khambete H, Jain S. Development of antifungal emulsion based gel for topical fungal infections. IJPRD 2011; 2(12): 18 - 22.

26. Singh PB, Choudhury PK. Penetration enhancers for transdermal drug delivery of systemic agents. J Pharm Res. 2007; 6(2): 44 - 50.

27. Shahin M, Hady SA, Hammad M, Mortada N. Novel jojoba oil-based emulsion gel formulations for clotrimazole delivery. AAPS Pharm Sci Tech 2011; 12: 239 - 247.

28. Kumar NPM, Patel MR, Patel KR, Patel NM. Emulgels: a novel approach to topical drug delivery. Int. J. Univ. Pharm. Bio Sci. 2013; 2: 134 - 148.

29. Joshi B, Singh G, Rana AC, Saini S and Singla V. Emulgel: A comprehensive Review on the recent advance in topical drug delivery. International Research Journal of Pharmacy 2011; 2(11): 66 - 70.

30. Mathew LK and Abraham S. Emulgel: An innovative approach for topical drug delivery. International Journal of Universal Pharmacy and Bio Sciences 2014; 3(4): 207-223.

31. Eswaraiah S, Swetha K, Lohita M, Preethi J and Reddy KK. Emulgel: review on novel approach to topical drug delivery. International Journal of Pharmaceutical Research 2014; 4(1): 4 - 11.

32. Pant S, Badola A, Baluni S and Pant W. A review on Emulgel novel approach for topical drug delivery system. World Journal of Pharmacy and Pharmaceutical Sciences 2015; 4(10): 1728 - 1743.

33. Patel J, Trivedi J and Chudhary S. Formulation and evaluation of Diacerin Emulgel for psoriatic arthritis. International Journal of Pharmaceutical Research 2014; 3(2): 625 - 638.

Received on 22.09.2021 Modified on 15.12.2021

Asian J. Res. Pharm. Sci. 2022; 12(2):163-168.

DOI: 10.52711/2231-5659.2022.00028