Stability of buffered benzylpenicillin and flucloxacillin for a paediatric outpatient parenteral antibiotic therapy service

Abstract

Introduction: Benzylpenicillin and flucloxacillin are commonly used in outpatient parenteral antibiotic therapy (OPAT). Published evidence supporting the stability of buffered infusions, in a variety of devices and concentrations, using an Australian commercially available buffer, to suit a paediatric setting is desirable. The aim of this study was to determine if multiple concentrations of buffered benzylpenicillin and flucloxacillin, prepared in suitable infusion devices, exposed to a variety of temperatures, maintained stability. Methods: Benzylpenicillin (15 and 60 mg/mL) and flucloxacillin (5 and 60 mg/mL) infusions in LV Elastomeric Infusor devices and sodium chloride 0.9% Viaflex bags were prepared as buffered and unbuffered solutions. Buffering was achieved by reconstituting antibiotic vials with sodium citrate 4%. Infusions were stored at 2–8°C for 6 days then 37°C for 24 h. Samples were taken on day 0, 1, 3, 6 and 7. The concentration, pH, colour and appearance were assessed at each time point. Results: The concentration of all day 7 buffered benzylpenicillin samples was maintained between 97.70–100.36% and flucloxacillin 98.7–100.66% of the initial concentration. Unbuffered solutions did not retain antibiotic potency over the same study period. There was minimal pH change in buffered benzylpenicillin samples from 6.66 to 5.5 and flucloxacillin 6.58 to 6.19. There was no visual change in colour or appearance. Conclusion: Buffered benzylpenicillin 15 and 60 mg/mL and flucloxacillin 5 and 60 mg/mL in LV Elastomeric Infusors and sodium chloride 0.9% Viaflex bags, appear chemically stable for 6 days refrigerated, and for a subsequent 24 h at 37°C.L20130005712021-07-06 <br />2021-09-28 <br />