ISSN-E 1995-9516 Universidad Nacional de Ingeniería COPYRIGHT © (UNI). TODOS LOS DERECHOS RESERVADOS http://revistas.uni.edu.ni/index.php/Nexo https://doi.org/10.5377/nexo.v33i01.10050 Vol. 33, No. 01, pp. 94-108/Junio 2020 THERMODYNAMIC INVESTIGATION OF PROMETHAZINE, LORATADINE, CETIRIZINE AND BUCLIZINE AS ANTIHISTAMINE DRUGS; MONTE CARLO AND SEMI-EMPIRICAL STUDIES INVESTIGACIÓN TERMODINÁMICA DE PROMETAZINA, LORATADINA, CETIRIZINA Y BUCLIZINA COMO MEDICAMENTOS ANTIHISTAMÍNICOS; MONTE CARLO Y ESTUDIOS SEMI-EMPÍRICOS Mina Zakeri1, Majid Monajjemi2*, Ali Ebrahimi3 1Department of Chemistry, Science and Research Branch, Islamic Azad University, Tehran, Iran 2Department of Chemical Engineering, Central Tehran branch, Islamic Azad University Tehran, Iran 3Department of chemistry, Computational Quantum Chemistry Laboratory, University of Sistan and Baluchestan, Iran *
[email protected] (recibido/received: 14-diciembre-2019; aceptado/accepted: 21-febrero-2020) ABSTRACT In this article, we discussed about four antihistamine drug called promethazine, loratadine, cetirizine and buclizine. Promethazine in this list is the only one in first generation antihistamine classification with CNS sedation effect and the other three belongs to second generation antihistamine group which are non- sedation and used to treat in many different anti-allergenic fields. In the following we optimized potential, kinetic and total energy of these molecules at body temperature (310 k˚) and environment temperature (298 k ˚) using Mont Carlo method in Amber force field in 500 ns. The quantum mechanics calculations and molecular structure of these molecules investigated using B3LYP level of theory with 6-31 G (d) as a basis set. Theoretical computations were performed to study thermodynamic parameters and frequency analysis. Electronic, thermal, zero point and gibs free energy and enthalpy were estimated in frequency analysis.