Stability of cefmetazole—doxycycline mixtures in sodium chloride and dextrose injections

SUMMARY This study involved the mixing of cefmetazole 1 and 2 Gm with doxycycline 100 and 200 mg, in sodium chloride and dextrose injections. The mixtures were stored either at ambient temperature for 96 h or at 4°C for 168 h followed by 8 h at ambient temperature. HPLC assay of both cefmetazole and doxycycline levels were performed at prescribed sampling times. Cefmetazole 1 Gm in doxycycline 100 and 200 mg mixtures, in sodium chloride injection was not stable up to 4 h, but cefmetazole 2 Gm in doxycycline 100 and 200 mg mixtures, in sodium chloride injection was stable for up to 24 h. The cefmetazole controls were stable for 72 h in sodium chloride injection. Cefmetazole 1 Gm with doxycycline 100 mg, in dextrose injection was stable up to 72 h. The 2 Gm cefmetazole and 100 mg doxycycline mixture in dextrose injection was stable for 96 h. Cefmetazole 1 Gm and doxycyline 200 mg in dextrose injection was stable up to 96 h, but the 2 Gm cefmetazole‐200 mg doxycycline mixture was only stable for 72 h. Cefmetazole controls in dextrose injection were stable for 24 h. Doxycycline 100 and 200 mg were stable with cefmetazole 1 and 2 Gm, in both sodium chloride and dextrose injections for 96 h at ambient temperature. Doxycycline control solutions were also stable for 96 h. Cefmetazole 1 and 2 Gm and doxycycline 100 and 200 mg were generally stable in both sodium chloride and dextrose injections at 4°C for 168 h, and at ambient temperature for 8 h. A precipitate was observed at 48 h with the cefmetazole 2 Gm‐doxycycline 100 mg mix in sodium chloride and at 8 h in dextrose injection. In both cases, removal from 4°C storage followed by storage and re‐assay at ambient temperature supported the re‐dissolution of one or both medications.