Degradation kinetics and mechanisms of a new cephalosporin, cefixime, in aqueous solution

✍ Scribed by Yoshihiro Namiki; Toyoshige Tanabe; Toshimitsu Kobayashi; Junko Tanabe; Yoshiko Okimura; Shigetaka Koda; Yukiyoshi Morimoto

• Publisher: John Wiley and Sons
• Year: 1987
• Tongue: English
• Weight: 703 KB
• Volume: 76
• Category: Article
• ISSN: 0022-3549
• DOI: 10.1002/jps.2600760305

✦ Synopsis

Hydrolysis of cefixime in buffer solutions (pH 1-9) at 25 "C and a constant ionic strength of 0.3 was investigated using ion-pair reversed-phase HPLC. Hydrolysis rates followed pseudo first-order kinetics; the rate of hydrolysis of cefixime was very slow at pH 4-7, slightly faster at lower pH, and quite rapid at higher pH. In the early stages of hydrolysis, six major degradation products were isolated and identified: a p-lactam ring-opened product and a 7-epimer (basic conditions), three lactones derived from intramolecular cyclization between the 2-carboxyl and 3-vinyl groups (acidic conditions), and an aldehyde derivative involving a 7-acyl moiety (neutral conditions). Principal degradation pathways for cefixime were found to involve initial cleavage of the p-lactam ring.