Sergio Mangiafico

pH-Dependent stability of azithromycin in aqueous solution and structure identification of two new degradation products

ABSTRACT The degradation profile of azithromycin in buffered solutions was investigated using HPLC and found to be pH dependent in the range of 6.0–7.2. Desosaminylazitromycin, derived from hydrolytic loss of cladinose of the parent molecule, was the major degradation product at pH 6.0 but its amount progressively decreased moving toward pH 7.2. Two additional unreported degradation products were also observed and their structures were fully elucidated by MS‐ and NMR‐spectroscopy to be associated with opening of the macrocyclic lactone ring. HIGHLIGHTSDegradation of azithromycin in the pH interval 6.0–7.2 was investigated by HPLC.Impurity profiling of azythromycin was found dependent on the pH of the solution.Two novel degradation products were identified and spectroscopically characterized.Degradation of azythromycin can occur through opening of the lactone ring.