CEFEPIME/ENMETAZOBACTAM: Physicochemical Stability of a Novel β-Lactam/β-Lactamase Inhibitor Combination in Syringes and Elastomeric Devices

Background: Cefepime/enmetazobactam (FEP/META) is a novel fixed-dose β-lactam/β-lactamase inhibitor combination. The objective was to study the physicochemical stability of the approved daily dose in polypropylene syringes and elastomeric devices over a 24 or 72 h period to understand the feasibility of using FEP/META in prolonged infusions and its use for outpatient parenteral antibiotic therapy (OPAT). Methods: Solutions of FEP/META were prepared in 0.9% NaCl or 5% dextrose (D5W) and stored in syringes (6 g/1.5 g/48 mL) or silicone and polyisoprene elastomeric devices (EDs) at 6 g/1.5 g/120 mL and 6 g/1.5 g/240 mL: syringes were tested at 22–25 °C over a 24 h period, polyisoprene EDs at 2–8 °C over 72 h period, and silicone and polyisoprene EDs at 32 °C over a 24 h period. The solution was considered stable if it retained more than 90% of its initial concentration (Ci), no pH variation (±1 unit), no significant visual change, and with compliant subvisual examination. Liquid Chromatography–Electrospray Ionization–Quadrupole Time-of-Flight–Mass Spectrometry was utilized to identify intermediate degradation products. Results: At the daily dose, FEP/META retained >90% of its Ci up to 12 h in 0.9% NaCl and 24 h in D5W when stored in syringes. In silicone ED, stability was enhanced up to 24 h in D5W at all concentrations. The solution was chemically stable for 24 h when stored in polyisoprene ED in 0.9% NaCl at 2–8 °C. Conclusions: FEP/META combination showed prolonged stability with physicochemical integrity up to 12–24 h in all containers and conditions. It appears to be stable for prolonged infusions and for OPAT.