[Stability of oxyethyltheophylline solutions for injection]

The testing of oxyethyltheophylline solutions for injection involved the separate study of their constituents, theophylline and ethophylline, particular attention being given to the behaviour of both these active agents under thermal stress in acid or alkaline medium. Acids exert little effect on the stability. In contrast to theophylline, ethophylline is rapidly decomposed by alkaline hydrolysis into two degradation products. The preparative production of ethophyllidine evidenced that ethophylline is decomposed under alkaline stress, via ethophyllidinecarboxylic acid (not isolated), to the heretofore unknown ethophyllidine (unequivocally characterized by analysis), which is the major cause of the instability of oxyethyltheophylline solutions for injection.