溴甲纳曲酮水溶液降解动力学研究

Degradation Kinetics of Methylnaltrexone Bromide Aqueous Solution

目的研究溴甲纳曲酮在水溶液中的降解动力学特征,考察溴甲纳曲酮的降解影响因素,为其制剂的研究提供必要的实验结果和数据。方法通过经典恒温实验,应用HPLC测定溴甲纳曲酮在不同温度、pH值、光照和Fe3+浓度条件下的降解动力学参数,用阿仑尼乌斯公式预测其有效期和活化能。结果溴甲纳曲酮在水溶液中的降解反应级数为n=1,其水溶液最稳定的pH值在3.51左右;随着温度升高,溴甲纳曲酮降解速率增加,在常温水溶液中的有效期t0.9=145 d;Fe3+和光照能促进溴甲纳曲酮的降解。结论溴甲纳曲酮在水溶液中的降解属近似一级动力学过程,降解速率与温度成正相关,pH对溴甲纳曲酮的降解有一定的影响,Fe3+和光照对溴甲纳曲酮的降解速率影响较明显。为制剂的研发提供了必要的实验结果和数据。

OBJECTIVE To investigate the degradation kinetic characteristics of methylnaltrexone bromide aqueous solution and to study the factors that influence methylnahrexone bromide degradation, thus to provide necessary data for the pharmaceutical re- search. METHODS Classical isothermal method was employed to evaluate the degradation kinetic profile of methylnaltrexone bro- mide under different temperatures, pH values, illumination and concentrations of Fe3 ~. The activation energy and shelf life were pre- dicted with Arrbenius equation. RESULTS The degradation of methylnahrexone bromide aqueous solution complied with first order kinetics. The aqueous solution was stable in an environment of pH 3.51, the higher the temperature was, the larger the degradation ki- netic rate constant was. The shelf-life of the aqueous solution was 145 d at room temperature ; and the illumination, as well as the exist- ence of Fe3＋ could both facilitate the degradation of methylnahrexone bromide. CONCLUSION The degradation of methylnahrexone bromide follows apparent first-order kinetics, and the degradation kinetic rate is affected by Fe3＋ and illumination. Moreover, its degra- dation remarkably and positively correlates with temperature, pH also has an effect on the degradation rate. The kinetic profile provides basis for the investigation of the degradation mechanism and necessary experimental data for the future pharmaceutical research.