Emulgel: An Advanced Review

Gels are a relatively newer class of dosage form created by entrapment of large amounts of aqueous or hydro alcoholic liquid in a network of colloidal solid particles. Gel formulations generally provide faster drug release compared with conventional ointments and creams. In spite of many advantages of gels, a major limitation is in the difficulty in delivery of hydrophobic drugs. So to overcome these limitations, emulgels are prepared. When gels and emulsions are used in combined form, the dosage forms are referred as Emulgels. Emulsions possess a certain degree of elegance and are easily washed off whenever desired. They also have a high ability to penetrate the skin. Emulgels for dermatological use have several favourable properties such as being thixotropic, greaseless, easily spreadable, easily removable, emollient, non-staining, water-soluble, longer shelf life, bio-friendly, transparent & pleasing appearance. Other important factor is to extend the drug release of even hydrophilic drugs by making w/o emulgel. Key WordsEmulgel, Gel, oils, gelling agents INTRODUCTION Over last decades of the treatment of illness has been accomplished by conventional routes namely oral, sublingual, rectal, parental etc. Topical drug administration is a localized drug delivery system anywhere in the body through ophthalmic, rectal, vaginal and skin as topical routes. The main advantage of topical delivery system is to bypass first pass metabolism . Avoidance of the risks and inconveniences of intravenous therapy and of the varied conditions of absorption like pH changes, presence of enzymes, gastric emptying time are other advantages of topical preparations . These are applying a wide spectrum of preparations for both cosmetic and dermatological, to their healthy or diseased skin. Dermatological products are diverse in formulation and range in consistency from liquid to powder but the most popular products are semisolid preparation. Within the major group of semisolid preparations, the use of transparent gels has expanded both in cosmetics and in pharmaceutical preparations. Gels are a relatively newer class of dosage form created by entrapment of large amounts of aqueous or hydro alcoholic liquid in a network of colloidal solid particles. Gel formulations generally provide faster drug release compared with conventional ointments and creams. In spite of many advantages of gels a major limitation is in the difficulty in delivery of hydrophobic drugs. So to overcome this limitation emulgels are prepared and with their use even a hydrophobic drug can enjoy the unique properties of gels. When gels and emulsions are used in combined form the dosage forms are referred as Emulgels. In fact, the presence of a gelling agent in the water phase converts a classical emulsion into an emulgel. Direct (oil-in-water) system is used to entrap lipophilic drugs whereas hydrophilic drugs are encapsulated in the reverse (water-in-oil) system. Emulsions possess a certain degree of elegance and are easily washed off whenever desired. They also have a high ability to penetrate the skin. Emulgels for dermatological use have several favourable properties such as being thixotropic, greaseless, easily spreadable, easily removable, emollient, non-staining, water-soluble, longer shelf life, bio-friendly, transparent & pleasing appearance. Fig.; Emulgel structure Factors Affecting Topical Absorption of Drug 8 Physiological Factors 1. Skin thickness. 2. Lipid content. 3. Density of hair follicles. 4. Density of sweat glands. 5. Skin pH. 6. Blood flow. 7. Hydration of skin. 8. Inflammation of skin Physiochemical Factors 1. Partition coefficient. 2. Molecular weight (<400 Dalton). 3. Degree of ionization (only unionized drugs gets absorbed well). 4. Effect of vehicles K. P. Mohammed Haneefa et al /J. Pharm. Sci. & Res. Vol.5(12), 2013, 254 258