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.

了解用于维持粘土基质中药物释放的络合过程的热力学非常重要。几种表征技术以及等温量热法用于研究模型阳离子药物（地尔硫卓盐酸盐，DIL）在药物粘土体系（硅酸铝镁，MAS）上的吸附过程。X 射线粉末衍射 (XRPD)、衰减全反射傅里叶变换红外光谱 (ATR-FTIR) 和光学显微镜证实了 DIL-MAS 配合物的成功形成。来自复合物的药物定量表明，在 2 M HCl 介质中 DIL 降解为盐酸脱乙酰基地尔硫卓 (DC-DIL) 的不同介质中表现出不同的行为。这里也是，作者首次报告了 DIL 和 MAS 发生的两个绑定过程。因此提出了一个竞争者结合模型，并且获得的热力学表明它们的结合过程是焓驱动的并且在熵上是不利的。该信息对于配方设计师来说非常重要，因为在选择适当的培养基以及配合物的结合性质时应给予注意和考虑。