INTRODUCTION:

DEFINATION:

Emulgels can be defined as it a new topical drug delivery method that can be created by mixing gel with water in emulsion and have benefits of both gels and emulsion¹ Emulgel is a biphasic system comprising an apolar internal phase (emulsion) within an aqueous gel base^.[2] Emulgel have a number of advantages over traditional semisolid dosage forms, emulgel have ability to deliver drugs in controlled manner.Emulgel is thixotropic, greaseless, easily spreadable, easily removable, emollient, and transparent in appearance.²Emulgel are emulsions, either oil-in-water or water-in-oil type.³In recent years, there has been great interest in use of novel polymers with complex function as emulsifiers and thickeners because the gelling capacity of these compounds allow the formulation of stable emulsion. The presence of gelling agent in water phase converts a classical emulsion into an emulgel.⁴

Regional delivery involves the application of drug to the skin for purpose of treating diseases or alleviating symptoms in deep tissue beneath the application⁵

Fig .1 structure of emulgel

Classification of Emulgel:

A) Based on the type of API

B) Based on the type of emulsion

A) Based on the type of API-

1) Herbal/Polyherbal:

e.g., i) Cosmetic emulgel for skin care from field pumpkin.

ii) Anti-psoriatic emulgel from babchi oil and Gum Guggle.

2) Allopathic:

e.g., i) Diclofenac diethyl Ammonium Emulgel (Voltaren) by Novartis Pharma.⁶

B) Based on type of Emulsion:

1) Macroemulgel:

These are popular type of Emulgel where the particle size of droplets of emulsion is more than 400 nm. They are visually blurred but the droplets are easily observed under microscope. The surface active agent is added to the microemulgel which provide stability as it is thermodynamically unstable.

2) Nanoemulgel:

When nanoemulsion is mixed with gel it is called as nanoemulgel. The particle size of droplets of nanoemulsion is less than 100 nm. Nanoemulgel are thermodynamically stable transluscent dispersion of oil and water which can be stabilized by interfacial film of surfactant and cosurfactant. Nanoemulgel formulation has transdermal and dermal delivery properties both in vivo and in vitro. Nano emulsions enhance transdermal permeation of many drugs over the conventional topical formulation such as emulsion and gel.

3) Microemulsion:

Microemulsions are mixtures of two phases, oil and water, that are stabilized by a surfactant. The surfactant allows the microemulsion to remain clear and thermodynamically stable. The droplets in a microemulsion are small, ranging from 10 to 100nm, and do not coalesce. In addition to oil, water, and surfactant, a microemulsion may also contain a co-surfactant. Microemulsions may have unique properties, such as extremely low interfacial tension and the ability to dissolve both aqueous and oil-soluble compounds. The ingredients in microemulsion could help the drug permeate faster by lowering the stratum corneum’s diffusion barrier⁷

Advantages of Emulgel:

1) Easy termination of therapy.

2) Better loading capacity.

3) Improve Bioavailability.⁸

4) Better stability can be achieved by using a wider base of support.

5) No Intensive sonication

6) Avoiding First pass metabolism.

7) More selective for a specific site^.9

Disadvantages of Emulgel:

1) Skin irritation on contact dermatitis

2) The potential for allergic reactions

3) The poor permeability of some drugs through the skin presents a significant clinical problem, due to skin barrier for many molecules, including drugs.

4) Drugs of large particle size are difficult to absorb through the skin^.10

Ideal Properties of Drug to formulate as Emulgel:

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

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

§ Half life of drug 10hr or less.

§ Partition coefficient i.e. Log p (octanol-water) between 0.4-0.8

§ Having a skin permeability coefficient more than 0.5 × 10^-3cm/hr

§ Oral bioavailability and therapeutic index should be low.

§ Drug should be non-irritating and non-sensitizer having a less polarity¹¹

Different excipients used in formulation of emulgel:

1) Aqueous Material: The aqueous phases used are water, alcohol, etc.

2) Oil: Oils are used to prepare emulgel. Mineral oils and paraffin are used either alone or in combination. Usually the oil which has the maximum solubilizing potential for the selected drug candidate, is preferred as oily phase for the formulation of emulsion¹²

3) Emulsifiers: Emulsifiers are compounds that are used to prepare emulsions. Some examples of emulsifiers are span 80, tween 80, stearic acid, and sodium stearate.

4) pH adjusting agents: These are the agent which are added into formulation to adjust the pH of the formulation.¹³

5) Gelling Agents: Gelling agents are used to prepare gels, which enhance the consistency of the preparation and used as thickening agent.

6) Penetration Enhancer: Penetration Enhancer help to increase the penetration of drug into the skin¹⁴

Method of preparation:

Emulgel is prepared by mixing emulsion in a gel base. It involves three steps:

Step 1: Preparation of emulsion:

a) Preparation of oil phase-The oil phase of emulsion is prepared by dissolving propylene glycol in light liquid paraffin.

b) Preparation of aqueous phase-The aqueous phase was prepared by dissolving drug in ethanol.

Both the oil and aqueous phase were separately heated to 75^oC then the oil phase was added to aqueous phase with continuous stirring until cooled to a room temperature.

Step 2: Preparation of gel:

The gel base were prepared by dispersing polymer such as carbapol 934 in purified water with constant stirring at amoderate speed and the pH are adjusted to 2-6 using triethanolamine(TEA).

Step 3: Formulation of Emulgel:

The obtained emulsion is mixed with gel base with gentle stirring to obtain Emulgel.¹⁵

Applications-

1) Lipophilic drugs can effortlessly combine into gel.

2) Controlled release pattern of drug which have smaller half-life.

3) Gives better patient compliance.

4) Being gelling nature it gives a good spreadability and easy to apply.

5) Economical i.e. it can formulate in very reasonable price.

6) It gives better stability than other dosage form.

7) It has the good loading capacity than noisome, liposome.

8) It enhances solubility of lipophilic drugs.¹⁶

Different marketed formulation prepared for emulgel:

Sr. No.	Brand Name	Active Ingredient	Uses
1	Voltarol 1.16% emulgel	Diclofenac Diethylammonium salt	Anti -inflammatory
2	Miconaz-H emulgel	Miconazole nitrate, hydrocortisone	Topical corticosteroid and antifungal.¹⁷
3	Denacine emulgel	Clindamycine phosphate	Anti-Acne
4	Diclon emulgel	Diclofenac Diethylamine	Anti -inflammatory
5	Cataflam emulgel	Diclofenac potassium	Anti inflammatory¹³
6	Diclomax emulgel	Diclofenac sodium	Anti inflammatory
7	Denacine emulgel	Clindamycin phosphate	Anti-acne¹⁸
8	Clinagel	Clindamycine phosphate, allantonin	Anti-acne
9	Avindo gel	Azithromycine	Anti-Acne
10	Cloben gel	Clotrimazole, Betamethasone	Anti -inflammatory
11	Kojivit gel	Kojic acid, dipalmitate acid	Anti -aging¹⁹

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Received on 26.08.2023 Modified on 11.09.2023

Asian J. Res. Pharm. Sci. 2023; 13(4):330-332.

DOI: 10.52711/2231-5659.2023.00056