Factors affecting the stability of ceftriaxone sodium in solution on storage

Abstract The influence of storage temperature (37, −20, −40 and −70°C), solvent (water, 0.9% NaCl, 5, 10 and 20% dextrose) and antibiotic concentration (10, 25, 50 and 100 μg/ml) on ceftriaxone disodium bioactivity was studied by means of a quantitative bacteriological agar gel diffusion assay. The loss of bioactivity, at 37°C, occurred in two phases, rapid degradation within the first 24 h, followed by a second phase of steadily decreasing bioactivity. At freezing temperatures, the degradation of ceftriaxone followed a monoexponential first-order process. Admixtures can be stored for 3 months at −70°C, 2 months at −40°C, except 5% dextrose ( f 90 = 51 days), and 1 month at −20°C without significant loss of antibiotic bioactivity. Ceftriaxone disodium was more stable in water solution, followed by 0.9% NaCl and 5, 10 and 20% dextrose solutions. The stability of ceftriaxone decreased with increasing concentration. Drawing several samples in the first 24 h was proved to be important to determine the shelf-life ( t 90 ) when it is less than 24 h.