[Degradation of Azlocillin and Mezlocillin / I. Behaviour in biological material and buffer (author's transl)]

Abstract

The degradation of 6-[(R)-2-(2-oxo-imidazolidine-1-carboxamido)-2-phenyl-acetamido] penicillanic acid Na-salt (azlocillin, Securopen) and 6-[(R)-2-[3-methylsulfonyl-2-oxoimidazolidine-1-carboxamido]-2-phenyl-acetamido ] penicillanic acid Na-salt (mezlocillin, Baypen), two chemically related acylureido penicillins, was tested in biological material (plasma and urine) and borate buffer at 37 degrees C over the time period of at least 6 h. In fresh human urine (pH 5.0) no degradation could be observed. In freshly prepared human plasma (pH 7.6) degradation was independent of the initial concentration and amounted to no more than 5%. No difference could be noted between the degradation in plasma or buffer, respectively, indicating that direct aminolysis did not play an important role in the degradation process. The extent of degradation could be demonstrated to be pH-dependent. After 8 h incubation at pH 9.0 azlocillin concentration was decreased to 70% and mezlocillin concentration to 50%, respectively, of the initial concentration. Since urinary pH values up to 8.5 are reported the urinary recovery of the substance could be influenced by alkaline pH.