Stability of Nine Time-Dependent Antibiotics for Outpatient Parenteral Antimicrobial Therapy (OPAT) Use

<b>Background:</b> The use of an elastomeric diffuser is favored to administer outpatient antibiotic therapy. A study published in 2022 highlighted the instability of several antibiotics in elastomeric devices at 37 °C. The objective was to evaluate the stability of nine time-dependent antibiotics that are unstable at 37 °C at lower concentrations and a reduced storage temperature of 32 °C. <b>Methods:</b> Chemical stability was assessed by pH measurement and high-performance liquid chromatography. Physical stability was evaluated by visual and subvisual inspection. The solutions were considered stable if the remaining drug percentage was ≥90%, the maximum variation in pH was less than 1, the particle count was within acceptable limits and the visual aspect remained unchanged after storage. <b>Results:</b> Solutions showing stability for 24 h are composed of 12.5 mg/mL cefiderocol in NS (normal saline) and 50-133 mg/mL piperacillin in NS-D5W (5% dextrose). Additionally, 12.5 mg/mL amoxicillin in NS; 12.5 mg/mL cefepime in NS-D5W; 12.5 mg/mL cefiderocol in D5W; 25 mg/mL cefiderocol in NS-D5W; 12.5 mg/mL cefotaxime in NS-D5W; 12.5 mg/mL cefoxitin in NS-D5W; 12.5 mg/mL ceftazidime in NS-D5W; 25 mg/mL ceftazidime in NS; 25 mg/mL cloxacillin in NS-D5W; and 25-50 mg/mL oxacillin in NS were shown to be stable for 12 h. Notably, 25 mg/mL amoxicillin in NS, 50 mg/mL cloxacillin in NS and 25 mg/mL oxacillin in D5W were shown to be stable for 8 h. <b>Conclusions:</b> These 12-24 h stability data indicate that these antibiotics can be administered by continuous infusion using only one-two elastomeric devices per day, facilitating outpatient parenteral antimicrobial therapy (OPAT).