Role of condensed water in the solid state stability of enalapril maleate

The physicochemical stability of enalapril maleate was investigated in the presence of fourteen different excipients divided into four different classes. The attached files contain results that are divided into two chapters: One) The extent of a drug-excipient interaction by following the chemical stability Two) Investigation of the water sorption characteristics of the excipients. The chemical stability of enalapril maleate was followed using HPLC. The water sorption characteristics of the excipients were examined from a humidity range of 0 to 90%RH. The resulting behavior was sectioned in layers by application of three models: Brunauer-Emmet-Teller (BET), Guggenheim-Andersen-de Boer (GAB) and Young-Nelson models. The GAB-model was applied using the software Universal analysis software of TA instruments. The BET-constant was calculated and applied in Young-Nelson model where parameters were determined using a multiple regression technique.

本研究考察了马来酸依那普利（enalapril maleate）在14种分为4类的不同辅料存在下的理化稳定性。附件中的研究结果分为两部分：其一，通过监测化学稳定性来表征药物-辅料相互作用程度；其二，对辅料的吸水特性展开研究。本研究采用高效液相色谱法（High Performance Liquid Chromatography，HPLC）监测马来酸依那普利的化学稳定性；辅料的吸水特性在0至90%相对湿度（RH）范围内进行测试。针对所得吸附行为，采用三种模型进行分层解析：布鲁瑙尔-埃米特-特勒（Brunauer-Emmet-Teller，BET）模型、古根海姆-安德森-德博尔（Guggenheim-Andersen-de Boer，GAB）模型以及扬-纳尔逊（Young-Nelson）模型。GAB模型的计算使用TA仪器公司的Universal分析软件完成；BET常数经计算后代入扬-纳尔逊模型，该模型的参数通过多元回归技术确定。