In order to study a change in mixed injection solution, stability of aqueous solution of injectable sodium cefapyrin (Cefatrexyl, CEPR), a cefalosporin antibiotic, was investigated at 15°, room temperature (20°±5°) and 37°, and degradation products as an indication of the stability were monitored with thin-layer chromatography, bioautography and absorption spectrophotometry. The residual potency was also measured by bioassay. The following results were obtained: 1) Changes in appearance and pH were not opserved in the CEPR solution for 7 days, and the residual potency was 96.4% after 24 hrs the potency was 98.3% and color intensity was increased. The potency at 20° and 37° was 94.3 and 67.3%, respectively. 2) The CEPR solution produced a white precipitate at pH 5.00, and the color intensifies at alkaline pH. It was stable for 24 hrs at pH 6.00-10.00 at 5°, and at pH 6.00-9.00 at 20°. 3) The CEPR solution produced desacetyl cefapyrin, a desacetyl group of CEPR, at 20° 14 days after its preparation, and at 37° 7 days after.
