Chemical stabilities of cefuroxime sodium and metronidazole in an admixture for intravenous infusion.

The chemical stabilities of cefuroxime sodium and metronidazole, when mixed together for intravenous infusion, were studied by high-performance liquid chromatography (HPLC). The critical factor in the stability of the admixture was the degradation of cefuroxime sodium. At 25 degrees C, cefuroxime degraded by first-order kinetics with a rate constant of 7.04 x 10(-2)/day and a t90 (time to reach 90% of the original concentration) of 36 h. At 4 degrees C the rate constant was 5.23 x 10(-3)/day with a t90 of 20 days, however, over the time-scale studied, the kinetics approximated to zero-order at this temperature. The mixture was also stable with respect to metronidazole, nitrite ion and appearance. A 7-day storage life at 4 degrees C can be given to the mixture.