Available online www.jocpr.com Journal of Chemical and Pharmaceutical Research, 2017, 9(3):74-84 Research Article ISSN : 0975-7384 CODEN(USA) : JCPRC5 74 Pharmacokinetics Studies of Mirtazapine Loaded Nanoemulsion and Its Evaluation as Transdermal Delivery System Kenneth Maduabuchi Ezealisiji 1* , Chika John Mbah 2 , Patience Osadebe 2 and Rui Krause 3 1 Department of Pharmaceutical Chemistry, Faculty of Pharmaceutical sciences, University of Port Harcourt, Port Harcourt, Nigeria 2 Department of Pharmaceutical and Medicinal Chemistry, Faculty of Pharmaceutical sciences, University of Nigeria, Nsukka, Nigeria 3 Department of Chemistry, Rhodes University, Grahamstown, South Africa _____________________________________________________________________________ ABSTRACT The in vitro study of skin permeability plays a vital role in the selection of candidates for the development of transdermal dosage forms. In this work, mirtazapine nanoemulsions were developed, characterized and the pharmacokinetics were studied. Nanoemulsions were prepared using the spontaneous emulsification mechanism. Surfactant (sodium lauryl sulfate) and cosurfactant (propylene glycol) were mixed in different volume ratios. Pseudoternary phase diagrams were developed using the aqueous titration method. Nanoemulsions formed were characterized by particle size, polydispersity index, and zeta potential. Analysis of variance (ANOVA) of data was evaluated and optimized nanoemulsions with Smix ratio of (3:1) were obtained. The zeta potentials of the optimized nanoemulsions were –94.000±0.001 and -92.900±0.004 mV for nanoemulsion formulation 16 (NE16) and nanoemulsion formulation 17 (NE 17) respectively, while mean droplet size (photon correlation microscopy) for the same optimized formulations were 56.00±0.01, 24.00±0.01 nm respectively. There was good correlation between mean droplet size result obtained from PCS and the values obtained using transmission electron microscope (46.0 ± 12.15 and 38.2 ± 7.62 nm respectively). The in vitro skin permeation study using excised rat skin showed the permeability coefficient values for the optimized nanoemulsions to be 0.0284±0.005 and 0.0332±0.002 cm/h for formulations NE 16 and NE 17 respectively, while that of the control (mirtazapine suspension in distilled water) was 0.0019±0.003 cm/h. The relative bioavailability was observed to be 79.17 % and 44.38 % compared to the calculated 16.80 % for the oral suspension thus making the developed Nanoemulsion more potent than previous oral formulations. Keywords: Nanoemulsion; Transdermal delivery; Mirtazapine; Thermodynamic stability _____________________________________________________________________________ INTRODUCTION Drug molecules prior to been absorbed into the systemic blood circulation, have to spend some time in both aqueous solutions of the gastrointestinal tract and lipid phase of the biological membrane. For this process to occur efficiently, aqueous and lipid solubility of the drug are required. However, literature has shown that about 90 % of new drugs and many existing drugs are poorly water soluble and therefore tend to exhibit very poor bioavailability [1]. To improve the bioavailability of these lipophilic drugs, various recent techniques utilizing lipid based systems including nanoemulsions have been reported [2,3,4,5]. Nanoemulsion, a thermodynamically stable transparent or translucent formulation is prepared by the spontaneous emulsification method that involves mixing oil, water, surfactant, and cosurfactant, in the correct proportion, with mild agitation. A number of studies have found