Using a planetary health lens to quantify intravenous use of bioequivalent antimicrobials when oral administration is feasible

Background: Health care accounts for 4.6% of Canada's greenhouse gas (GHG) emissions, 25% of which comes from medications. Antimicrobials with high bioavailability offer no additional benefit when given intravenously, except when oral (PO) administration is not feasible. Intravenous (IV) formulations have a higher carbon footprint than their PO counterparts. IV-to-PO switch strategies benefit patients and the health care system by reducing line-related adverse events, nursing time, length of hospital stay, and costs and can also reduce carbon emissions. Our primary objective was to quantify IV use of bioequivalent antimicrobials when PO administration is feasible. Secondary objectives were to determine GHG emissions and antimicrobial costs associated with unnecessary IV use of bioequivalent antimicrobials. Methods: We performed a retrospective, cross-sectional study of hospitalized adults who received IV azithromycin, ciprofloxacin, clindamycin, cotrimoxazole, fluconazole, levofloxacin, linezolid, metronidazole, moxifloxacin, or voriconazole at Vancouver General Hospital on five dates. We determined the proportion of patients receiving these antimicrobials who met criteria for PO administration. We also applied a life cycle assessment (LCA) to assess the GHG emissions of the antimicrobial drug delivery systems using OpenLCA with the Ecoinvent database. Using these data, we calculated the GHG emissions and costs associated with unnecessary IV use. Results: In total, 128 patients were identified. Seventy-eight (61%) met IV-to-PO switch criteria on the audit dates. Most eligible patients were admitted to general surgery, internal medicine, or critical care. The antimicrobial with the highest IV-to-PO switch eligibility was metronidazole (51%), most often prescribed for intra-abdominal infections. Over the five study dates, potential GHG savings were about 80,000 gCO 2 -eq. Potential annual cost savings were about $59,000. Conclusion: Over 60% of patients receiving highly bioavailable IV antimicrobials were eligible for PO therapy, highlighting an opportunity to optimize prescribing. Promoting an IV-to-PO switch can improve patient outcomes and reduce environmental impact, supporting both patient-centred care and planetary health.