Stavchansky S, Wallace J E, Wu P
J Pharm Sci. 1983 May;72(5):546-8. doi: 10.1002/jps.2600720517.
A stability-indicating GLC method for the analysis of promethazine hydrochloride in polyethylene glycol delivery systems is reported. This method is capable of distinguishing the intact drug from its thermal and photodegradation products. A linear relationship between peak height ratio (promethazine-promazine) and promethazine concentration is found up to a concentration of 600 micrograms/ml. Kinetic studies were performed to determine the photolytic and thermal degradation rates of promethazine hydrochloride as a function of pH. The activation energies at pH 2.98, 3.94, and 5.12 were obtained from linear Arrhenius plots and were found to be 6601, 5888, 5570 cal/mole, respectively. The first-order rate constant increased with increasing pH. The photolytic degradation of promethazine hydrochloride does not follow simple first-order kinetics.
报道了一种用于分析聚乙二醇给药系统中盐酸异丙嗪的稳定性指示气相色谱法。该方法能够区分完整药物与其热降解和光降解产物。发现峰高比（异丙嗪-丙嗪）与异丙嗪浓度之间在浓度高达600微克/毫升时呈线性关系。进行动力学研究以确定盐酸异丙嗪的光解和热降解速率与pH的函数关系。从线性阿伦尼乌斯图获得了pH 2.98、3.94和5.12时的活化能，分别为6601、5888、5570卡/摩尔。一级速率常数随pH升高而增加。盐酸异丙嗪的光解降解不遵循简单的一级动力学。
