Bhardwaj Sunny Piyush, Singh Saranjit
Department of Pharmaceutical Analysis, National Institute of Pharmaceutical Education and Research, Sector 67, S.A.S. Nagar, Punjab 160062, India.
J Pharm Biomed Anal. 2008 Jan 7;46(1):113-20. doi: 10.1016/j.jpba.2007.09.014. Epub 2007 Sep 19.
In the present study, comprehensive stress testing of enalapril maleate was carried out according to ICH guideline Q1A(R2). The drug was subjected to acid (0.1N HCl), neutral and alkaline (0.1N NaOH) hydrolytic conditions at 80 degrees C, as well as to oxidative decomposition at room temperature. Photolysis was carried out in 0.1N HCl, water and 0.1N NaOH at 40 degrees C. Additionally, the solid drug was subjected to 50 degrees C for 60 days in a dri-bath, and to the combined effect of temperature and humidity, with and without light, at 40 degrees C/75% RH. The products formed under different stress conditions were investigated by LC and LC-MS. The LC method that could separate all degradation products formed under various stress conditions involved a C18 column and a mobile phase comprising of ACN and phosphate buffer (pH 3). The flow rate and detection wavelength were 1 ml min(-1) and 210 nm, respectively. The developed method was found to be precise, accurate, specific and selective. It was suitably modified for LC-MS studies by replacing phosphate buffer with water, where pH was adjusted to 3.0 with formic acid. The drug showed instability in solution state (under acidic, neutral, alkaline and photolytic stress conditions), but was relatively stable in the solid-state, except formation of minor products under accelerated conditions. Primarily, maximum degradation products were formed in acid conditions, though the same were also produced variably under other stress conditions. The LC-MS m/z values and fragmentation patterns of two of the five products matched with enalaprilat and diketopiperazine derivative, previously known degradation products of enalapril. Also, m/z value of another product matched with an impurity listed in the drug monograph in European Pharmacopoeia. Rest two were hitherto unknown degradation products. The products were characterized through LC-MS fragmentation studies. Based on the results, a more complete degradation pathway for the drug could be proposed.
在本研究中，按照国际人用药品注册技术协调会（ICH）指南Q1A(R2)对马来酸依那普利进行了全面的应力测试。该药物在80℃下分别置于酸性（0.1N盐酸）、中性和碱性（0.1N氢氧化钠）水解条件下，以及在室温下进行氧化分解。光解在40℃的0.1N盐酸、水和0.1N氢氧化钠中进行。此外，将固体药物在干浴中于50℃下放置60天，并在40℃/75%相对湿度下考察有光和无光时温度与湿度的综合影响。通过液相色谱（LC）和液相色谱-质谱联用（LC-MS）对不同应力条件下形成的产物进行了研究。能够分离各种应力条件下形成的所有降解产物的LC方法采用C18柱和由乙腈（ACN）和磷酸盐缓冲液（pH 3）组成的流动相。流速和检测波长分别为1 ml min⁻¹和210 nm。结果发现所建立的方法精密、准确、专属且具有选择性。通过用水替代磷酸盐缓冲液对其进行了适当修改以用于LC-MS研究，并用甲酸将pH调节至3.0。该药物在溶液状态下（在酸性、中性、碱性和光解应力条件下）表现出不稳定性，但在固态下相对稳定，不过在加速条件下会形成少量产物。主要是在酸性条件下形成的降解产物最多，不过在其他应力条件下也会不同程度地产生。五个产物中的两个产物的LC-MS m/z值和碎片模式与依那普利拉和二酮哌嗪衍生物匹配，这两种是依那普利先前已知的降解产物。另外，另一个产物的m/z值与欧洲药典中该药物专论列出的一种杂质匹配。其余两个是迄今未知的降解产物。通过LC-MS碎片研究对这些产物进行了表征。基于这些结果，可以提出该药物更完整的降解途径。
