PMID: 22579003May 15, 2012Paper

An insight into thermodynamic relationship between polymorphic forms of efavirenz

Journal of Pharmacy & Pharmaceutical Sciences : a Publication of the Canadian Society for Pharmaceutical Sciences, Société Canadienne Des Sciences Pharmaceutiques
Renu ChadhaDharamvir Singh Jain

Abstract

The aim of the work is to study the crystallization of efavirenz to understand the preferential formation of various polymorphic forms, to establish their identity, to study the transformation between the polymorphic forms on heating and to determine their free energy. Slow crystallization from different solvents under controlled conditions was employed to prepare various crystalline forms. The TGA and DSC were used to study their thermal behavior and inter-conversion of these forms. The calorimetrically determined enthalpies of solution and solubility data are utilized to determine the transition temperatures. Six polymorphic forms of efavirenz are identified and characterized completely. The TGA scans of all the forms did not show any mass loss indicating absence of hydrate or solvate. The thermally induced transformations are observed in the DSC scans of five forms II-VI indicating them to be metastable which are converted to stable higher melting forms. The melting temperature and enthalpy of fusion of lower melting (FormL) and higher melting forms (FormH) reveal that four of these polymorphic pairs are monotropically related. The enthalpies of solution of FormL are found to be more exothermic as compared to corresponding F...Continue Reading

Citations

Apr 25, 2018·Pharmaceutical Development and Technology·E CappellettoP Scardi
Mar 17, 2021·Critical Reviews in Analytical Chemistry·Jaya P AmbhorePrashant S Kharkar
Jan 15, 2015·Journal of the American Chemical Society·Baiju P Krishnan, Kana M Sureshan

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