A Review on Microemulsion Based Gel : A Novel Approach for Enhancing Topical Delivery of Hydrophobic Drug

In current scenario, an augmentation in topical formulations by virtue that it can be prepared by altering physicochemical properties as well as furnishing more desirable localized action. It is imperious to adhere patient to topical formulations in dealing with chronic skin diseases like fungal infections, acne and psoriasis. One of the modernistic technology in Novel Drug Delivery System used topically is Microemulsion based Gel carry virtue of bi-fold control release i.e. microemulsion as well as gel. For hydrophobic drugs, Microemulsion based gel has been emanated as a felicitous topical drug delivery system and demonstrated as fortune for dermal care and cosmetology. When microemulsion is included in gel, its stability is also raised. Microemulsions have been confirmed for increment in cutaneous absorption of both lipophilic and hydrophilic API’s when correlated to conventional vehicles. This versatile, thermodynamically stable, colloidal dispersion of water and oil is stabilized by surfactant and co-surfactant. It is prepared by different polymers, emulsifier and owing to the gelling capacity of these compounds give improvement to stable emulsions as surface and interfacial tension is reduced while at that moment increment in the viscosity of the aqueous phase. For dermatological treatment, microemulsion based gel has certain beneficial properties such as being thixotropic, greaseless, easily spreadable, easily removable, emollient, non-staining, water soluble, longer shelf life, bio-friendly, transparent & pleasing appearance. In present review, we discussed certain advantages of microemulsion based gel in pharmaceuticals, along with its preparation and characterization. Bhumika M. Chhatrani 1* and Dr. Dhiren P. Shah 2 1 M. Pharm, Department of Pharmaceutics, Shree Naranjibhai Lalbhai Patel College of Pharmacy, Umrakh 394 345, Gujarat, India. 2 Principal, Shree Naranjibhai Lalbhai Patel College of Pharmacy, Umrakh 394 345, Gujarat, India. Submission: 7 March 2017 Accepted: 10 March 2017 Published: 25 March 2017 www.ijppr. humanjournals.com Citation: Bhumika M. Chhatrani et al. Ijppr.Human, 2017; Vol. 8 (4): 19-35. 20 INTRODUCTION In last few decades, the treatment of several diseases has been accomplished by administering drug to human body via various routes, namely, oral, sublingual, rectal, parental etc. The topical drug delivery system is generally used in where other systems of drug administration fail or it is mainly used in local skin infection like fungal infection, acne, psoriasis. Topical drug delivery can be defined as the application of a drug containing formulation to the skin to directly treat cutaneous disorder. In these modern days, pharmaceutical research work is focused to fulfill the therapeutic needs of patients. Most of active pharmaceutical ingredients developed are hydrophobic in nature, so to develop new drug delivery system microemulsion has good impact on effective delivery of hydrophobic drugs. [1] Human skin is a uniquely engineered organ that permits terrestrial life by regulating heat and water loss from the body whilst preventing the ingress of noxious chemicals or microorganisms. Many widely used topical agents like ointments, creams and lotions have numerous disadvantages. They are usually very sticky causing uneasiness to the patient when applied. Moreover, they also have less spreading coefficient and need to apply with rubbing. They also exhibit the problem of stability, due to all these factors, within the major group of semisolid preparations; the use of transparent gels has increased both in cosmetics and in pharmaceutical preparations. [2] Topical gels are transparent or translucent semisolid formulations containing a high ratio of solvent/gelling agent. Gels are defined as semi-rigid system in which the movement of the dispersing medium is restricted by interlacing three-dimensional networks of particles or solvated macromolecules of the dispersed phase. They are non-invasive and have patient compliance, less greasy, easily removed from the skin, cost effective, reduction of doses as compare to oral dosage forms, localized effect with minimum side effects, improving drug bioavailability, reducing dose frequency and stabilizing drug delivery profiles. [3, 4] In spite of many advantages of gels, a major limitation is in the delivery of hydrophobic drugs. So to overcome this limitation microemulsion based approach is being used, so that even a hydrophobic therapeutic moiety can enjoy the unique properties of gels. First, oil-inwater microemulsion is prepared, which is then gelled by mixing with a gelling agent. Emulsified gel is stable one and superior vehicle for hydrophobic or poorly water soluble drugs. In short microemulsion based gels are the combination of microemulsion and gel. [5] www.ijppr. humanjournals.com Citation: Bhumika M. Chhatrani et al. Ijppr.Human, 2017; Vol. 8 (4): 19-35. 21  Advantages of Topical Drug Delivery Systems: [6]  Avoidance of the first pass metabolism.  Convenient and easy to apply.  Avoidance of risks and inconveniences of the intravenous therapy and of diverse conditions of absorption like pH changes, presence of enzymes, gastric emptying time.  Easily terminate the medications, when needed.  Deliver drug more selectively to a specific site.  Avoidance of the gastrointestinal incompatibility.  Providing utilization of drugs with short biological half-life, narrow therapeutic window.  Improved patient compliance.  Provide suitability for self-medication.  Achievement of effectiveness with lower total daily dose of drug by continuous drug input.  Avoids fluctuation in drug levels, interand intra patient variations.  A quite large area of application in comparison with buccal or nasal cavity.  Ability to deliver drugs more selectively to a specific site.  Disadvantages of Topical Drug Delivery System: [5]  Skin irritation of contact dermatitis may occur due to the drug and excipients.  Possibility of allergenic reactions.  Enzyme in epidermis may denature the drug. ANATOMY AND PHYSIOLOGY OF THE SKIN: [7, 8, 9] Skin is one of the most readily accessible organs on human body for topical administration and is the main route of topical drug delivery system. The total area of skin is about 20 square feet. The skin protects us from microbes and the elements help to regulate body temperature and permit the sensations of touch, heat and cold. The pH of the skin varies from 4 to 5.6. Sweat and fatty acid secreted from sebum influence the pH of the skin surface. The skin is composed of three layers: www.ijppr. humanjournals.com Citation: Bhumika M. Chhatrani et al. Ijppr.Human, 2017; Vol. 8 (4): 19-35. 22 Figure 1 Skin structure [9]