Use of Ceftriaxone and Benzylpenicillin in Outpatient Parenteral Antimicrobial Therapy: Spectrum vs Cost.

Background: The application of antimicrobial stewardship (AMS) principles may entail increased cost to allow for narrower-spectrum therapy. Prescribing benzylpenicillin (BP) and ceftriaxone (CRO) for outpatient parenteral antimicrobial therapy (OPAT) demonstrates the complex challenge of this principle. The aim of this study is to analyze the use of BP and CRO in our OPAT program, including indications and relative cost. Methods: We analyzed all adult patients in our OPAT program who received intravenous BP or CRO over 1 year. We identified a "crossover group" of patients who could have received either agent. Economic comparison was based on acquisition cost of the therapy (drug, infuser, and preparation costs). Results: Of 105 eligible patients, 54 (51%) and 51 (49%) received BP and CRO, respectively. Forty (38%) patients were suitable for either agent; of these, the majority (n = 31, 78%) were treated with BP. Economic analysis demonstrated that the average daily cost of BP therapy was $93.76/d (AUD) vs $1.23/d for CRO. Thus, across our OPAT programs, we had an additional average cost of $92.53/patient/d to use BP instead of CRO. Program-wide the annual additional cost of using BP and thus applying this AMS strategy was $68 386.12. Conclusions: BP is often selected over CRO by clinicians, where possible, as recommended by the Australian guidelines; however, BP is associated with higher daily acquisition costs. More broadly, a number of narrower-spectrum agents may involve significantly higher costs than comparators; as such, the $92.53/d to prevent CRO exposure can be considered when applying other antimicrobial-substitution AMS interventions in an acute health care setting.