An Overview on Emulgels (Al03-2016)

Emulgel: An Overview

Mustafa Hamido

1. ABSTRACT

Emugel is a semisolid dosage form used in cosmetic and pharmaceutical preparations. It has witnessed an increase of its use in the recent years due to the advantages it offers over other semisolid dosage forms. It has better spread ability, stability, loading capacity and even better control release. It is prepared by mixing emulsion with gel base with continuous stirring.

2. INTRODUCTION

Figure 1 Emulgel Structure source: Haneefa, K.M., Mohanta, G.P. and Nayar, C., 2013. Emulgel: An Advanced Review. J. Pharm. Sci. & Res, 5(12), pp.254-258.

Emulgel is a kind of topical pharmaceutical preparation made by mixing emulsion and gel preparation 1:1 ratio (1). The most famous drug was formulated using this technique was Volatern emulgel. Most topical preparations available in the market are either creams, emulsions, ointments or gels. But why formulators use emulgel dosage form to formulate their drugs?


3. WHY EMULGEL?

Figure 2 Emulgel in tube

Actually there are plenty of reasons push them to do so. Gels has low preparation cost, cooling effect, better spreadability and better skin absorption. Moreover, they are even easier in preparation and offer better control release (2). They consist of water and gelling agent like carbomer. The largest amount of any gel is water. Thus, it has low preparation cost and many formulators prefer them over other topical dosage forms (3).
The main problem which could face any formulators when choosing gels to formulate the drug molecule is its solubility in water. Hydrophobic moieties are the main obstacle facing formulators when they choose gels to formulate drugs. These moieties can't be formulated as gels as the main constituent of them is water (4). To overcome this problem and to get the advantages of gels in topical preparation, emulgel is the solution available. Emulgel is used mainly to get the advantages of gels in case the API is not soluble in water (5). The hydrophobic moieties is prepared as emulsions and then mixed with a plain gel. By this way, formulators surpass the difficulty of dissolving hydrophobic moieties in water which for the base of gels.

4. HOW IT IS PREPARED

Figure 3 How Emulgel is made Source: Alecos Care

Emulgels are prepared into two steps. The first step is preparing gel and emulsion. The second step is mixing both emulsion and gel into 1:1 ratio (6).

a- Emulsions

Figure 4 HLB Scale Source: https://en.wikipedia.org/wiki/Hydrophilic-lipophilic_balance

The first step is preparing emulsion where the API is dispersed in it. Emulsion is a topical preparation which has two phases: the oil phase and water phase. Emulsions are prepared in two ways: W/O or O/W. The type of preparation depends on the choosing of the oil phase type. Water in oil or oil in water emulsion are used to prepare emulgel. Both oil phase and water phase are put into two separate tanks and all constituents like preservatives, additives and surfactants are added and mixed (7). Choosing surfactants depend on the type of the emulsion. Oil in water emulsions need surfactants with high HLB value and vice versa for water in oil emulsion. The main role for surfactants in such preparations is to let the oil and water mix together by reducing surface tension between the two phases (8).

Figure 5 HLB Values and Properties Source: http://dowac.custhelp.com/app/answers/detail/a_id/3277/~/surfactant-basics---definition-of-hlb,-and-how-it-applies-to-emulsions

Thus the two phases are moved to a bigger tank and mixed together till we get a homogeneous soft creamy product called emulsion. The difference between cream and emulsion is in the thickness of the product. Creams are thicker and more viscous than emulsion due to the amount of water in it. Creams have lower amount of water than emulsions.

b- GELS

The second step is preparing gel. Gels are semisolid preparation prepared using gelling agents which form a cross linked system. They form an interlacing three dimensional network to restrict the movement of the dispersing medium. Gels are classified into two categories: Hydrogels and organogels. Hydrogels are gels where water is used as a base. It is a single phase preparation where water form more than 90% of the preparation (9). Organgels are multiphase preparation. Organic solutions are used as a base where it is mixed with hydrogel to form a multiphase organogel.
There are many classes of gelling agents. They include: cellulose, carbomer and poloxamers. Each class have number of agents under it. Each one have different properties and different characteristics (10). For example, methyl cellulose is a cellulose gelling agent which make thin gels. Carpobol 934P is a crabomer gelling agent effective in thick preparation like emulsion, suspensions and other topical formulation.  Usually carbomers gelling agents are used in in aqueous and hydroalcoholic systems. Hydrogles are formed by mixing the gelling agent with water. Then, an external energy is applied on the mixture. It is blended together till form a jelly material.

c- MIXING GELS AND EMULSIONS

Emulgels are two phases preparation. The first phase is the emulsion and the second is the gel. Emulgels are formed by mixing the emulsion phase with the gel phase into 1:1 ration (11). Emulsion is added to gel phase and mixed continuously till we get a homogeneous medium called emulgel.

5. CONCLUSION

Emulgels are topical preparations used for various applications. They are prepared by mixing gels with emulsion into 1:1 ratio. Emulsions are two phase preparation where water forms the first phase and oil forms the second phase. The two phases are mixed together using surfactant which decrease the surface tension between the two phases and ease their mixing. Gels are topical preparations formed using a gelling agent like carbomers which is dispersed in water phase in hydrogels and blended together till form a jelly like product. Usually emulgels are chosen by formulator to formulate their drugs due to number of reasons including overcoming the insolubility of the drugs into water when they are willing to make gels for their advantages.

6. References:

(1) Hardenia, A., Jayronia, S. and Jain, S., 2014. Emulgel: An Emergent Tool In Topical Drug Delivery. International Journal of Pharmaceutical Sciences and Research, 5(5), p.1653.
(2) Asija, R., Sharma, R. and Gupta, A., 2013. Emulgel: A novel approach to topical drug delivery. Journal of Biomedical and Pharmaceutical Research, 2(6), pp.91-94.
(3) Asija, R., Sharma, R. and Gupta, A., 2013. Emulgel: A novel approach to topical drug delivery. Journal of Biomedical and Pharmaceutical Research, 2(6), pp.91-94.
(4) Shah, A.A., Kamdar, K., Shah, R. and Keraliya, R.A., 2013. Emulgel: a topical preparation for hydrophobic drugs. PharmTechMedica, 2, pp.370-376.
(5) Kute, S.B. and Saudagar, R.B., 2013. Emulsified gel A Novel approach for delivery of hydrophobic drugs: An overview. J. Adv. Pharm. Edu. & Res, 3(4).
(6) Hardenia, A., Jayronia, S. and Jain, S., 2014. Emulgel: An Emergent Tool In Topical Drug Delivery. International Journal of Pharmaceutical Sciences and Research, 5(5), p.1653.
(7) D’Souza, W.Z. and Gude, M.R., 2015. FORMULATION, DESIGN, DEVELOPMENT AND EVALUATION OF EMULGEL FOR TOPICAL DELIVERY OF MELOXICAM IN THE TREATMENT OF RHEUMATOID ARTHRITIS. Indo American Journal of Pharmaceutical Research, 5(3), pp.1271-1279.
(8) "Dow Answer Center". Dowac.custhelp.com. N.p., 2016. Web. 17 May 2016.
(9) Peppas, N.A., Bures, P., Leobandung, W. and Ichikawa, H., 2000. Hydrogels in pharmaceutical formulations. European journal of pharmaceutics and biopharmaceutics, 50(1), pp.27-46.
(10) Mujawar, N.K., Ghatage, S.L. and Yeligar, V.C., ORGANOGEL: FACTORS AND ITS IMPORTANCE.
(11) Hardenia, A., Jayronia, S. and Jain, S., 2014. Emulgel: An Emergent Tool In Topical Drug Delivery. International Journal of Pharmaceutical Sciences and Research, 5(5), p.1653.