Hindawi Publishing Corporation Journal of Pharmaceutics Volume 2013, Article ID 501082, 9 pages http://dx.doi.org/10.1155/2013/501082 Research Article Optimization of Metronidazole Emulgel Monica Rao, Girish Sukre, Sheetal Aghav, and Manmeet Kumar Department of Pharmaceutics, AISSMS College of Pharmacy, Kennedy Road, Maharashtra, Pune 411 001, India Correspondence should be addressed to Monica Rao; monicarp_6@hotmail.com Received 4 September 2012; Revised 27 November 2012; Accepted 10 December 2012 Academic Editor: Anna Wesolowska Copyright © 2013 Monica Rao et al. is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. e purpose of the present study was to develop and optimize the emulgel system for MTZ (Metronidazole), a poorly water soluble drug. e pseudoternary phase diagrams were developed for various microemulsion formulations composed of Capmul 908 P, Acconon MC8-2, and propylene glycol. e emulgel was optimized using a three-factor, two-level factorial design, the independent variables selected were Capmul 908 P, and surfactant mixture (Acconon MC8-2 and gelling agent), and the dependent variables (responses) were a cumulative amount of drug permeated across the dialysis membrane in 24 h (1 ) and spreadability ( 2 ). Mathematical equations and response surface plots were used to relate the dependent and independent variables. e regression equations were generated for responses 1 and  2 . e statistical validity of the polynomials was established, and optimized formulation factors were selected. Validation of the optimization study with 3 con�rmatory runs indicated a high degree of prognostic ability of response surface methodology. Emulgel system of MTZ was developed and optimized using 2 3 factorial design and could provide an effective treatment against topical infections. 1. Introduction When gels and emulsions are used in a combined form the dosage forms are referred to as emulgels [1, 2]. As the name suggests they are the combination of emul- sion/microemulsion and gel. In recent years, there has been great interest in the use of novel polymers with complex functions as emulsi�ers and thickeners because the gelling capacity of these compounds allows the formulation of stable emulsions by decreasing surface and interfacial tension and at the same time increasing the viscosity of the aqueous phase. In fact, the presence of a gelling agent in the water phase converts a classical emulsion into an emulgel. Both oil-in-water and water-in-oil emulsions are used as vehicles to deliver various drugs to the skin [3]. Emulsions possess a certain degree of elegance and are easily washed off whenever desired. ey also have a high ability to penetrate the skin. Emulgels for dermatological use have several favorable properties such as being thixotropic, greaseless, easily spread- able, easily removable, emollient, nonstaining, water soluble, having longer shelf life, biofriendly, transparent, having and pleasing appearance [4]. Several antifungal and antibacterial agents are avail- able in the market in different topical preparations (e.g., creams, ointments, and powders for the purpose of local dermatological therapy). One of these antibacterial agents is Metronidazole (MTZ), which has antibacterial properties. MTZ is used for the treatment of acne vulgaris, skin lesions, wound drainage, and wound odor. MTZ possesses poor water solubility and hydrophobicity; hence such drugs pose problems in a topical drug delivery. Hence, for solubilization of MTZ, formulation of microemulsion-based gel appeared to be a viable approach. In the development of emulgel dosage form, an impor- tant issue is to design an optimized formulation with an appropriate drug diffusion rate in a short period of time and minimum number of trials. Many statistical experimental designs have been recognized as useful techniques to opti- mize the process variables. For this purpose, a computer- based optimization technique with a 2-level factorial design utilizing a polynomial equation has been widely used. is technique requires minimum experimentation and time, thus is far more effective and cost-effective than the conventional methods of formulating emulgel dosage forms. e aim of