DEGRADATION KINETICS AND ISOMERIZATION OF CEFDINIR, A NEW ORAL CEPHALOSPORIN, IN AQUEOUS-SOLUTION .1.

Hydrolytic degradation products of cefdinir were studied in acidic (pH 1), neutral (pH 6), and basic (pH 9) solutions. Seven major degradati on products were isolated by preparative and/or high-performance liqui d chromatography and characterized by UV, IR, H-1-NMR, and mass spectr a. To clarify degradation pathways in each pH solution, kinetic and pr oduct analyses during hydrolysis of cefdinir were carried out along wi th the followup reaction of representative degradation products. Cefdi nir was shown to degrade via two major degradation routes: beta-lactam ring-opening and pH-dependent isomerizations (lactonization, epimeriz ation at C-6 or C-7, syn-anti isomerization of N-oxime function).