Compatibility and stability of linezolid injection admixed with aztreonam or piperacillin sodium.

OBJECTIVE

To evaluate the physical compatibility and chemical stability of linezolid (Zyvox-Pharmacia) 200 mg/100 mL admixed with aztreonam (Azactam-Squibb) 2 grams and separately with piperacillin sodium (Pipracil-Lederle) 3 grams over 7 days at 4 degrees C and 23 degrees C.

DESIGN

Controlled experimental trial.

SETTING

Laboratory.

INTERVENTIONS

Test samples were prepared by adding the required amount of aztreonam or piperacillin sodium to separate bags of linezolid injection 200 mg/100 mL.

MAIN OUTCOME MEASURES

Physical compatibility and chemical stability based on drug concentrations initially and after 1, 3, 5, and 7 days of storage at 4 degrees C and 23 degrees C.

RESULTS

All of the linezolid admixtures with aztreonam and with piperacillin sodium were clear when viewed in normal fluorescent room light and with a Tyndall beam. Measured turbidity and particulate content were low and exhibited little change throughout the study at both storage temperatures. High-performance liquid chromatography analysis found little or no loss of linezolid in any sample stored at either temperature throughout the study. Aztreonam in the linezolid admixtures was stable for 7 days, exhibiting less than 5% loss at 4 degrees C and 9% loss at 23 degrees C. Piperacillin sodium in the linezolid admixtures was stable for 7 days at 4 degrees C, exhibiting no loss, but was stable for only 3 days at 23 degrees C with losses of about 5%. Losses had increased to 9% to 12% after 5 days of storage at room temperature.

CONCLUSION

Admixtures of linezolid 200 mg/100 mL with aztreonam 2 grams or piperacillin sodium 3 grams were physically compatible and chemically stable for at least 7 days stored at 4 degrees C and for 7 days or 3 days, respectively, at 23 degrees C.