_____________________________________________________________________________________________________ *Corresponding author: E-mail: rutesh.dave@liu.edu; Journal of Pharmaceutical Research International 20(1): 1-10, 2017; Article no.JPRI.37901 ISSN: 2456-9119 (Past name: British Journal of Pharmaceutical Research, Past ISSN: 2231-2919, NLM ID: 101631759) Investigate the Effect of Fatty Acids on Rheological Properties and In vitro Permeability of Escitalopram Oxalate from Hydroxypropyl Cellulose Gel Formulations Nisarg Modi 1,2 , Marina Borovinskaya 2 , Fotios Plakogiannis 2 and Rutesh Dave 1* 1 Division of Pharmaceutical Sciences, Arnold and Marie Schwartz College of Pharmacy and Health Sciences, Long Island University, Brooklyn, NY-11201, USA. 2 Transdermal Research Pharm Laboratories, Pharmaceutical R&D Department, LLC, Long Island City, NY-11101, USA. Authors’ contributions This work was carried out in collaboration between all authors. All authors read and approved the final manuscript. Article Information DOI: 10.9734/JPRI/2017/37901 Editor(s): (1) Rafik Karaman, Professor, Bioorganic Chemistry, College of Pharmacy, Al-Quds University, USA. Reviewers: (1) Norma Aurea Rangel Vazquez, Mexico. (2) Filip Nina, University of Medicine and Pharmacy Gr. T. Popa Iasi, Romania. Complete Peer review History: http://www.sciencedomain.org/review-history/22137 Received 1 st November 2017 Accepted 28 th November 2017 Published 2 nd December 2017 ABSTRACT The present studies evaluate rheological properties and in-vitro permeability properties of Escitalopram Oxalate (ECO) containing hydroxypropyl cellulose (Klucel HF, HPC) gels prepared with different carbon chain length containing fatty acids. The formulations were prepared by mixing solvent, escitalopram oxalate and kulcel HF (HPC) in homogenizer at 25000 RPM. A controlled stress rheometer was used to study the effect of different number of carbon chain fatty acids on the rheological properties and microstructure of HPC gels. The in-vitro permeability study was performed using human cadaver skin in order to evaluate the enhancing effect of fatty acids. The studies demonstrated that as the carbon chain length increased (C 10 -C 18 ) the zero-shear viscosity, and yield stress value increased, which suggested that the stability of gel structure was increased with increase in carbon chain of fatty acids. Cohesive Energy was also depended on the carbon Original Research Article