Thermodynamics of clay – Drug complex dispersions: Isothermal titration calorimetry and high-performance liquid chromatography

Ana-Maria Totea, Juan Sabin, Irina Dorin, Karl Hemming, Peter Laity, Barbara Conway, Laura Waters, Kofi Asare-Addo

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

An understanding of the thermodynamics of the complexation process utilized in sustaining drug release in clay matrices is of great importance. Several characterisation techniques as well as isothermal calorimetry were utilized in investigating the adsorption process of a model cationic drug (diltiazem hydrochloride, DIL) onto a pharmaceutical clay system (magnesium aluminium silicate, MAS). X-ray powder diffraction (XRPD), Attenuated total reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR) and optical microscopy confirmed the successful formation of the DIL-MAS complexes. Drug quantification from the complexes demonstrated variable behaviour in the differing media used with DIL degrading to desacetyl diltiazem hydrochloride (DC-DIL) in the 2 M HCl media. Here also, the authors report for the first time two binding processes that occurred for DIL and MAS. A competitor binding model was thus proposed and the thermodynamics obtained suggested their binding processes to be enthalpy driven and entropically unfavourable. This information is of great importance for a formulator as care and consideration should be given with appropriate media selection as well as the nature of binding in complexes.
Original languageEnglish
Pages (from-to)78-85
Number of pages8
JournalJournal of Pharmaceutical Analysis
Volume10
Issue number1
Early online date5 Dec 2019
DOIs
Publication statusPublished - 1 Feb 2020

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