Objectives Published in vitro stability data for ceftolozane–tazobactam supports intermittent short duration infusions. This method of delivery is not feasible for many outpatient antimicrobial therapy services that provide only one or two visits per day. This study aimed to assess time, temperature and concentration-dependent stability of ceftolozane–tazobactam in an elastomeric infusion device for continuous infusion across clinically relevant ranges encountered in outpatient antimicrobial therapy.

Methods Ceftolozane–tazobactam was prepared to achieve initial concentrations representing total daily doses for ‘renal’, ‘standard’ and ‘high’ dose schedules in elastomeric infusion devices with a volume of 240 mL. Infusion devices incubated at room and body temperature were serially sampled over 48 hours. Refrigerated infusion devices were sampled over 10 days. Concentrations of ceftolozane and tazobactam were separately quantified using a validated ultra-high performance liquid chromatography–photodiode array method.

Results The greatest loss of ceftolozane occurred at 37°C, however, stability remained above 90% at 24 hours. Tazobactam was more stable than ceftolozane under these conditions. There was minimal loss at 4°C for either component over 7 days.

Conclusions Ceftolozane-tazobactam is suitable for ambulatory care delivered as a continuous infusion via an elastomeric infusion device.