INTRODUCTION:

Emulgels are a combination of an emulsion and a gel. Emulsions, either water in oil or oil in water, are gelled by mixing with a gelling agent, and thus Emulsified gel serves as a superior carrier for medications that are poorly water soluble or hydrophobic.¹The delivery of hydrophobic medicines is the biggest disadvantage of this gel, despite its many benefits. To address this limitation, an emulsion-based technique is being developed, allowing even a hydrophobic medicinal moiety to benefit from gel's unique features. In recent years, there has been a lot of interest in the use of new polymers as emulsifiers and thickeners. These compounds have a higher gelling capacity, which allows for the production of stable emulsions and creams. This works by raising the aqueous phase's viscosity while simultaneously lowering surface and interfacial tension.

A traditional emulsion becomes an emulgel when a gelling ingredient is present in the water phase. These Topical Emulgels are thixotropic, bio-friendly, water-soluble, greaseless, readily spreadable, emollient, easily removable, non-staining, have a longer shelf life, and have a clear and pleasing look.^2,3

Emulgel is divided into two sections:

1. Emulsion

2. Gel

Fig. 1: Emulgel structure⁴

RATIONALE OF EMULGEL AS A TOPICAL: DRUG DELIVERY SYSTEM:

A variety of medicinal items are applied to the skin or mucous membrane to improve or restore a basic skin function or to pharmacologically alter an action in the highlighted tissues. Topical or dermatological products are the names given to such items. Many commonly used topical treatments, such as ointments, creams, and lotions, have numerous drawbacks. When applied, they are extremely sticky, causing the patient discomfort. They also have a lower spreading coefficient and must be applied by rubbing, as well as a difficulty with stability. The usage of translucent gels in cosmetics and medicinal preparations has increased as a result of all of these variables within the principal group of semisolid preparations. A gel is a colloid that contains 99 percent liquid and is immobilised by surface tension between it and a macromolecular network of fibres formed by a little quantity of gelatin substance. Despite the many benefits of gels, one important drawback is the delivery of hydrophobic medicines. To address this constraint, an emulsion-based technique is being employed to successfully integrate and transport even a hydrophobic medicinal component via gels.^5,6

Advantages of emulgels⁷:

1. Increased loading capacity.

2. No sonication at all.

3. Avoid first-pass metabolism.

4. Avoid gastrointestinal incompatibility.

5. More site-specific selection.

6. Drugs that are hydrophobic are included.

7. Patient compliance has improved.

8. Convenient and straightforward.

9. Controlled release.

Disadvantages of emulgels⁷:

1. Contact dermatitis causes skin inflammation.

2. The possibility of allergic reactions

3. Some medicines have low permeability.

4. Large-particle drugs are difficult to absorb via the skin.

5. The occurrence of bubbles during emulgel formulation

DRUG DELIVERY ACROSS THE SKIN:

The epidermis is the skin's superficial layer, which is made up of stratified keratinized squamous epithelium that varies in thickness across the body. Skin as a target organ for dermatological disease identification and treatment. The skin works as a two-way barrier, preventing water and electrolyte absorption and loss. Three basic pathways are present in topical medication absorption: 1) transcellular 2) intercellular 3) Follicular. Drugs mostly flow through the tortuous path around corneocytes and through the lipid bilayer to reach the skin's viable layers. For many years, rubbing creams and gels into the skin have been used to administer pain relievers and antibacterial medications to an affected area of the body.

Fig. 2 : Drug delivery cross of section¹⁰

Gels and creams for vaginal yeast infections, topical creams for skin infections, and creams to relieve arthritis pain are just a few examples. Other medications can now be absorbed through the skin thanks to newer technologies (transdermal). These can be used to treat the entire body, not just the damaged parts (for example, the skin) (systemic).^8,9

FACTOR AFFECTING TOPICAL ABSORPTION OF DRUG:^11,12

Physiological factors

1. Skin thickness

2. Lipid content.

3. The density of hair follicles.

4. The density of sweat glands.

5. Skin pH.

6. Blood flow.

7. Hydration of skin.

8. Inflammation of skin.

Physicochemical factors:

1. Partition coefficient.

2. The molecular weight (<400 Dalton).

3. The degree of ionisation (only unionised drugs gets absorbed well).

4. Effect of vehicles.

Factors to be considered when choosing a topical preparation^13,14

1. The vehicle's effect, for example. The penetration of the active ingredient is improved by using an occlusive vehicle. The vehicle's own cooling, drying, emollient, or protecting properties are possible.

2. Match the type of lesions to the type of preparation. For acute weepy dermatitis, for example, keep away from greasy ointments.

3. Choose the correct form of preparation for the work. (For hairy regions, use a gel or lotion.)

4. Potential for irritation or hypersensitivity. Ointments and w/o creams are generally less irritating, whereas gels are. If you have an allergy to preservatives or emulsifiers, ointments are not for you.

For the preparation of emulgel some constituents are used including drug, which are:

1. Vehicle: Vehicle shall adhere to the ideal characters specified in the Pharmacopeias.

2. Aqueous material: Water, alcohol, and other aqueous phases are employed.

3. Oil: Emulsion preparation is done with oils. Mineral oils and paraffin are used separately or together .¹⁵

4. Emulsifiers: Emulsifiers are substances that help to make an emulsion. Span 80, tween 80, stearic acid, and sodium stearate are some examples.

5. Gelling agents: Gelling agents are used in the manufacture of gels to improve uniformity.

6. Penetration enhancers: Penetration enhancers aid in medication absorption through the skin

7. pH adjusting agent¹⁶

FORMULATION OF EMULGEL:

Step1: Preparation of gel using the gelling agent:

A sufficient amount of Carbopol 940 (1 percent w/w) was weighed and continuously stirred into warm distilled water. For 1-2 hours, the dispersion was allowed to hydrate. Other chemicals such as propylene glycol (10% w/w) and glycerol (10% w/w) were added to the aqueous dispersion after that, with constant stirring. A needed amount of medication (1% w/w) was added and spread properly. Triethanolamine was used to neutralise the dispersion to pH 6, and distilled water was used to adjust the final weight. To remove air bubbles, the gel was sonicated for 15 minutes and left overnight.

Step 2: Preparation of Emulsion:

Depending on whether the emulsion was created with oil in water or water in oil.

Step 3: Incorporation of the emulsion into gel base:

Finally, emulsion was mixed with gel base to create emulgel.¹⁷

Fig. 3: Flow chart of emulgel Preparation¹⁸

SUMMARY:

A great number of formulations are utilised in topical medication delivery systems, but each has its own set of drawbacks. The majority of these drawbacks are reduced by emulgel preparation. Throughout the project, the emulgel has proven to be the most convenient, better, and effective delivery technique. By incorporating emulsion within the gel, it becomes a dual control release system that addresses issues including phase separation, emulsion creaming, and improved stability. Emulgel, like emulsion and gel preparation, requires ingredients. The preparation of emulgel consists of three steps: emulsion preparation, gel preparation, and the combination of the two. Every formulation should be thoroughly evaluated. As a result, nearly twenty-five different types of evaluation methodologies are available, including light microscopy, spreadability, rheological studies, in-vitro drug release studies, and so on. The emulgel is commonly used nowadays. Miconaz-H-emulgel, Isofen emulgel, Diclon emulgel, and other emulgels are routinely used. Typically, emulgels are used to treat inflammation.

CONCLUSION:

Topical medicine delivery will be widely used in the next years to improve patient compliance. Emulgel is a new topical medication delivery method that works well with hydrophobic medicines. It has the ability to improve spreadability, adhesion, viscosity, and extrusion. They will become a prominent method of medicine delivery. Furthermore, they will be used to load hydrophobic medicines into a water-soluble gel base.

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Received on 28.05.2022 Modified on 30.09.2022

Asian J. Pharm. Res. 2023; 13(3):196-199.

DOI: 10.52711/2231-5691.2023.00037

Fig. 1: Emulgel structure4

Disadvantages of emulgels7:

Fig. 1: Emulgel structure⁴

Disadvantages of emulgels⁷: