A Review on Topical Emulgel

Vaibhav S. Jadhav*, Vishwajeet G. Thorat, Priyanka V. Gawali ,

Dr. Balmukund R. Rathi

SGSPS Institute of Pharmacy, Kaulkhed Akola, Maharashtra: 444001, India..

Correspondence: vaibhavpatil30078@gmail.com

INTRODUCTION

Treating local and general conditions can be done easily with topical pharmaceutical administration. One new area of dermatological pharmacology is the direct accessibility of the skin as an organ for diagnosis and treatment. The ability to deliver a large quantity of medication to a particular area, the avoidance of gastrointestinal incompatibility, and the avoidance of metabolic degradation linked to oral administration are only a few benefits of topical drug delivery systems. Many topical therapies offer better bioavailability by preventing the liver's first pass metabolism and guaranteeing consistent distribution over an extended period of time. The main disadvantages of topical dose forms are drug dissolution and diffusion in hydrophobic medication delivery and drug penetration through the stratum corneum in hydrophilic medication administration. When creating emulgel, both oil-in-waterAdditionally, water-in-oil emulsions are frequently used as carriers to administer hydrophilic and hydrophobic drugs to the skin. They are also effective at penetrating skin and dissolving medications^(1,2).

Focusing on emulgel is both fascinating and challenging because it is a novel area for topical medicine administration with few commercialized solutions to date. Understanding the advantages of emulsion and gel for topical drug administration is crucial before advancing to emulgel. With the aid of an emulsifying agent, one of the two immiscible phases of an emulsion—an internal or discontinuous phase—is disseminated into the other (an exterior or discontinuous phase). Emulsions are controlled-release systems. To provide a controlled effect, the drug particle that was trapped in the internal phase passes through the outer phase and then absorbs gently into the skin. Emulsions can be either water-in-oil or oil-in-water. According to USP, a gel is a semisolid system that is made up of liquid that has interpenetrated it. mixtures of big organic molecules or tiny inorganic particles. The gel contains a greater amount of aqueous or hydroalcoholic liquid in a cross-connected network of colloidal solid particles, which traps tiny drug particles and maintains controlled drug release^(3,4,5).

Advantages^(5,6)-

·         Drugs that are hydrophobic are included

·         Improved loading capacity and stability.

·         Controlled release is a term used to describe when something is released in a controlled manner

·         There will be no intensive sonication.

·         Avoiding the first-pass metabolic process

·         Keeping gastrointestinal incompatibility to a minimum

·         More focused on a single location.

·         Patient compliance has improved.

Disadvantages^(5,6)-

·         Contact dermatitis causes skin irritation

·         Allergic reactions are a possibility

·         Some medications have a low permeability through the skin.

Types of emulgel ^(2,6,7,8)

Microemulsion

Microemulsions are isotropic mixtures of a biphasic o/w systemic stabilized with a surfactant that is thermodynamically stable and optically clear. Droplets vary in size from 10 to 100nm and do not coalesce. It is made up of specific amounts of oil, co-surfactant, surfactant, and water. Microemulsions may have unique properties, including extremely low interfacial tension, a broad interfacial region, 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 barrier.

However, because of their low viscosity, the use of microemulsions in the pharmaceutical industry is limited due to their low skin retention ability. To address this limitation, gelling agents like HPMC K100M, Carbopol 940, and guar gum are added to the microemulsion to form microemulsion-based gels with a viscosity appropriate for topical application .

Nanoemulgel

Nanoemulsion is transparent (translucent) oil-water dispersions that are thermodynamically stable due to surfactant and cosurfactant molecules with a globule size range from 1nm to100 nm. When the emulsion is mixed with gel, the term Nanoemulgel is used. Many drugs have higher transdermal permeation with Nanoemulsion than with traditional formulations such as emulsions and gels. The Nanoemulsion possesses enhanced transdermal and dermal delivery properties in vivo as well as in vitro. Because of its high loading capacity and small globule size, the drug easily penetrates the skin and provides less therapeutic effect in a short period.

Macroemulsion gel

Emulgel with emulsion droplet particle sizes greater than 400nm. They are physically invisible, but under a microscope, the individual droplets can be seen clearly. Macroemulsions are thermodynamically unstable, but surface-active agents can help to stabilize them.

Components of emulgel ^(10,11,12)

Oils are used as an oil phase to prepare an emulsion.  Mineral oil and soft or hard paraffin are commonly used, either alone or in combination, in topically applied emulsions.Example: castor and mineral oils, which have laxative effects, are the most commonly used oils for oral and topical preparations .

Vehicles

In the emulgel preparation, oily and aqueous vehicles are used, and both hydrophobic and hydrophilic drugs are used.Examples of vehicles such as alcohol, water, and other aqueous materials are used in aqueous phase emulsions .

Emulsifiers

To improve shelf-life stability, an emulsifier is used to increase the emulsification of the preparation. Examples of emulsifying agents are Tween 80, Span80, Tween 20, stearic acid, etc .

Gelling agent

Gelling agents are used for preparing gels for any dosage form. It enhances the consistency of any formulation. Some examples of gelling agents are Carbopol 940, Carbopol 934, HPMC-2910, etc⁽¹⁷⁾ .

pH adjusting agent

These agents are used to maintain the pH of the formulation. Example: triethylamine, NaOH, etc.

Preparation of emulgel ^(15,18,)

Step 1: Formulation of gel base

The gel base is formed by dissolving a known quantity of polymer into DDW by mixing at moderate speed using a magnetic stirrer and pH is adjusted to 5-6.5 using Triethanolamine and NaOH .

Step 2: Formulation of O/W or W/O type of emulsion

Formulation of Smix in the appropriate ratio using a magnetic stirrer. Add the Smix into the oil phase dropwise under continuous stirring, which gives a clear emulsion⁽¹⁹⁾ .

Step 3: Formulation of emulgel- Add the prepared emulsion into gel base dropwise with continuous stirring using a homogenizer to get emulgel.

Table 1: Marketed formulation of emulgel ^(20,22)

Evaluation Parameters of  Emulgel

1)      Physical Appearance ⁽²³⁾ -

Color, homogeneity, consistency, and pH of the produced Emulsion compositions were visually evaluated.

2)      Spreadability^(23,24,25) -

                                   Spreadability is measured using this method based on the emulgel's 'Slip' and 'Drag' qualities. On this block a ground glass slide is fixed. This ground slide has an excess of  emulgel (approximately 2 gm) under observation.  After that, the emulgel is placed between this slide and a second glass  slide with the same size as the fixed ground slide, as well as a hook. For 5 minutes, a 1 kg weight is placed on top of the  two slides to release air and provide a consistent emulgel coating between the slides. The excess emulgel is scraped away  from the edges. After that, an 80-gram pull is applied to the top plate. The time (in seconds) required by the top slide to  cover a distance of 7.5 cm should be recorded with the help of string tied to the hook. The shorter interval, the better the spreadability. The formula was used to calculate spreadability.

S= M.L/T 

Where, 

S = spreadability.

M = Weight tied to upper slide.

L = Length of glass slides.

T = Time taken to detach the slides

3)      Extrudability study^(24,26)-

                                 To find out how much force is needed to extrude material from a tube, this empirical test is frequently used. The process for figuring out how much applied shear in the rheogram zone causes plug flow when the shear rate is higher than the yield value. The percentage of emulgel and emulgel extruded from a lacquered aluminum collapsible utilizing the gramme weight needed to extrude at least a 0.5 cm emulgel ribbon in 10 seconds is the basis for the extrudability evaluation of emulgel formulations in this study. As the amount extruded rises, extrudability gets better. The extrudability of each formulation is measured three times, and the average results are shown. The extrudability is then calculated using the following formula:

Extrudability = Weight used to extrude emulgel from tube (in gm) / Area (in cm2)

4)      Rheological studies⁽²⁴⁾ –

                                 A Brookfield  viscometer with  spindle no.18  at 100  rpm is  used to  determine the rheological  properties of  the various  emulgel compositions at 250○ C.

5)      Swelling Index^(27,28) –

                The swelling index was calculated by weighing 1 gramme of prepared topical emulgel on porous aluminium foil and placing it individually, undisturbed, in a 50 ml glass beaker with 10 ml of 0.1 N NaOH. After that, the samples are taken out of the beakers at different intervals and left in a dry location for a while before being weighed again. The following formula was used to determine the swelling index:

SW % = [Wt – Wo / Wo] × 100 

Where, 

SW % = Equilibrium percent swelling, 

Wt = Swollen Weight emulgel after time t, 

Wo = Initial weight of emulgel at time zero

6)      Skin irritation test ⁽²⁸⁾

Skin irritation test is usually done in skin of human volunteers with proper written consent. The prepared formulation is applied to the skin of the hand and observation is done to check for any undesirable effects

7)      Stability study ⁽²⁹⁾–

                          The  emulgels  are packed  in aluminium  collapsible  tubes (15  gramme)  and tested  for three  months  at 50°C,  250°C/60 percent  relative  humidity,  300°C/65  percent  relative  humidity,  and  400°C/75  percent  relative  humidity.  Each  month, samples are taken and evaluated according to ICH requirements for physical appearance, pH, rheological properties, drug content, and drug release profile, among other things

8)      Dilution test⁽²⁹⁾ –

                  By introducing Continuous phase to a  50 to 100  times aqueous dilution of emulgel, phase separation and clearness  were  visually verified.

9)      pH measurement⁽³⁰⁾

A digital pH meter is used to determine the pH of all prepared emulgel. Calibration of the pH meter is performed before using a standard buffer solution. 1 gm of the formulation is dissolved in distilled water until a uniform suspension is formed and is kept aside for 2 hours. After 2 hours the glass electrode is dipped in the suspension and the pH is measured 

10)  In Vitro release study^(31,32,33) –

                               The Franz diffusion cell is used to perform the drug release studies. Emulgel is applied uniformly throughout the egg membrane. The egg membrane is anchored between the donor and the receptor chamber of the diffusion cell. Next, freshly prepared PBS (pH 5.5) solution is added to the receptor chamber in order to solubilize the drug. The receptor chamber is stirred using a magnetic stirrer. A UV visible spectrophotometer must be used to evaluate the drug content of the appropriately diluted samples after the 1.0 ml aliquots of the emulgels have been collected at the proper intervals. The total amount of medication released at each time period is calculated using cumulative adjustments. Time is used as a function to determine how much medication is released overall the egg membrane.

CONCLUSION

Emulgels' advantages in spreadability, adhesion, viscosity, and extrusion will make them a popular drug delivery method.The widespread usage of topical medicine delivery devices is due to increased patient compliance. They will also be used to load hydrophobic medications onto gel bases that dissolve in water.

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