FACTORS AFFECTING THE STABILITY OF CEFTRIAXONE SODIUM IN SOLUTION ON STORAGE

The influence of storage temperature (37, -20, -40 and -70-degrees-C), solvent (water, 0.9% NaCl, 5, 10 and 20% dextrose) and antibiotic con centration (10, 25, 50 and 100 mug/ml) on ceftriaxone disodium bioacti vity was studied by means of a quantitative bacteriological agar gel d iffusion assay. The loss of bioactivity, at 37-degrees-C, occurred in two phases, rapid degradation within the first 24 h, followed by a sec ond phase of steadily decreasing bioactivity. At freezing temperatures , the degradation of ceftriaxone followed a monoexponential first-orde r process. Admixtures can be stored for 3 months at - 70-degrees-C, 2 months at - 40-degrees-C, except 5% dextrose (t90 = 51 days), and 1 mo nth at -20-degrees-C without significant loss of antibiotic bioactivit y. Ceftriaxone disodium was more stable in water solution, followed by 0.9% NaCl and 5, 10 and 20% dextrose solutions. The stability of ceft riaxone decreased with increasing concentration. Drawing several sampl es in the first 24 h was proved to be important to determine the shelf -life (t90) when it is less than 24 h.