International Journal of Pharma Research & Review, July 2014; 3(7):32-43 ISSN: 2278-6074 Raj Kumar Mishra et.al, IJPRR 2014; 3(7) 32 Review Article Nanoemulsion: A Novel Drug Delivery Tool *Raj Kumar Mishra, G. C. Soni, Rekha Mishra Institute of Pharmacy, Bundelkhand University, Jhansi, India. ABSTRACT Nanoemulsion (NE) is defined as an O/W or W/O emulsion producing a transparent product that has a droplet size from 20-200nm and does not have the tendency to coalesce. It is promising for transdermal delivery of drugs as an efficient route of drug administration. Several mechanisms have been proposed to explain the advantages of nanoemulsions for the transdermal delivery of drugs. In transdermal delivery, the goal of dosage design is to maximize the flux through the skin into systemic circulation. A useful strategy for improving percutaneous flux is to improve the concentration of drug or choose an appropriate vehicle for the transdermal delivery. The nanoemulsions system should be a promising vehicle due to powerful ability to deliver drug through skins. With these approaches, the aim of this present study is to review the potential of nanoemulsion formulation for transdermal delivery of pure phytopharmaceuticals and poorly soluble drugs. Some nanoemulsions have however exhibited sufficiently high level of stability for them to be proposed as vehicle for drug delivery. Using the transdermal route eliminates the side effects, increases patient compliance, avoids first-pass metabolism, enhance bioavailability and maintains the plasma drug level for a longer period of time. Cosmetics formulations require this delivery system in order to show their effect more prominently. Keywords: Transdernmal, poorly soluble drug, phytopharmaceuticals, nanoemulsion Received 26 May 2014 Received in revised form 23 July 2014 Accepted 25 July 2014 *Address for correspondence: Raj Kumar Mishra, Institute of Pharmacy, Bundelkhand University, Jhansi, India. E-mail: dr.rajmishra2103@gmail.com INTRODUCTION An emulsion is a system in which one fluid is dispersed in another with which it immiscible. Macroscopic separation of the phases is prevented by the addition of a suitable surfactant. In the vast majority of emulsion research, one of the liquid phases is water. The term "Nanoemulsion" [1] refers to a thermodynamically stable isotropic ally clear dispersion of two immiscible liquids, such as oil and water, stabilized by an interfacial film of surfactant molecules. A Nan emulsion is considered to be a thermodynamically or kinetically stable liquid dispersion of an oil phase and a water phase, in combination with a surfactant. The dispersed phase typically comprises small particles or droplets, with a size range of 5 nm-200 nm, and has very low oil/water interfacial tension. Because the droplet size is less than 25% of the wavelength of visible light, Nanoemulsions are transparent. The Nanoemulsion is formed readily and sometimes spontaneously, generally without high-energy input. In many cases a co surfactant or co solvent is used in addition to the surfactant, the oil phase and the water phase. Three types of Nan emulsions are most likely to be formed depending on the composition: 1. Oil in water Nan emulsions wherein oil droplets are dispersed in the continues aqueous phase 2. Water in oil Nan emulsions wherein water droplets are dispersed in the continuous oil phase; 3. Bi-continuous Nan emulsions wherein micro domains of oil and water are inter dispersed within the system.In all three types of Nan emulsions, the interface is stabilized by an appropriate combination of surfactants and/or co-surfactants.