Background Ceftolozane is a novel cephalosporin and commercially available in combination with the beta-lactamase inhibitor tazobactam under the brand name Zerbaxa. Cephalosporins exhibits, like all betalactams, a time-dependent antibacterial action. The concentration of the antibiotic at the site of infection should exceed the MIC of the underlying pathogen for at least 60%–70% of the dosing interval. According to the German prescribing information, Zerbaxa is administered as a short infusion in sodium chloride 0.9% or glucose 5%. However, clinical studies suggest that prolonged or continuous infusion of beta-lactam antibiotics can improve therapy success, especially in intensive care patients.

Purpose At present, there is insufficient data on the stability of ceftolozan/tazobactam in infusion solution for continuous infusion. German product information provides data on the stability under conditions of cooling (2°C–8°C) and light protection. Therefore, a stability test was carried out for 24 hours under real-world conditions.

Material and methods Solutions of ceftolozan/tazobactam (20/10 mg/L and 10/5 mg/L) in sodium chloride 0.9% and glucose 5%, respectively, were stored at room temperature for 24 hours without protection from light. Concentrations of ceftolozan/tazobactam were analysed at the start of the experiment and 1, 4, 8 and 24 hours thereafter using high-performance liquid chromatography with UV detection. In addition, at each analysis time point the solutions were visually examined and the pH values were determined.

Results Ceftolozan/tazobactam concentrations were stable for at least 24 hours (>98.5% of baseline) at both concentrations regardless of the used carrier solution. Visual appearance and pH values remained unchanged.

Conclusion Zerbaxa is stable in sodium chloride 0.9% and glucose 5% at room temperature for at least 24 hours and is therefore suitable for prolonged or continuous infusion.

References and/or acknowledgements None.