Efficacy of Protocol-Based Pharmacotherapy Management in Switching of Antibiotic Administration Routes and Dose Adjustment Based on Renal Function: A Before-After Study

Background: Antibiotics are crucial for treating infectious diseases, but their appropriate use is essential to minimize adverse reactions and resistance. This study evaluated the effectiveness of protocol-based pharmacotherapy management (PBPM) based on renal function in adjusting antibiotic dosage and implementing an intravenous-to-oral switch in older patients at high risk of drug-related adverse events. The study compared antibiotic treatment outcomes before and after PBPM implementation at Kyoto University Hospital. Method: This before-and-after study included patients aged ≥65 years diagnosed with community-acquired pneumonia or uncomplicated pyelonephritis at Kyoto University Hospital. The control group (January to December 2021) received conventional antibiotic treatment, whereas the PBPM group (June 2022 to May 2023) received treatment based on a protocol developed by pharmacists, emergency physicians, and infectious disease specialists. Primary and secondary outcomes included antibiotic administration duration, clinical response, adverse reactions, and costs. Results: The study included 78 patients (40 control, 38 PBPM). The PBPM group showed a significantly shorter total antibiotic treatment duration (9.6 ± 4.4 vs. 7.5 ± 2.4 days, p < 0.05) and intravenous administration duration (7.1 ± 2.8 vs. 5.6 ± 2.2 days, p < 0.01) compared with the control group. The PBPM group also demonstrated lower clinical treatment failure rates and reduced incidences of acute kidney injury and alanine aminotransferase elevation. Antibiotic costs per patient were 13% lower in the PBPM group. There were no significant differences in early clinical response, readmission rates, or mortality between groups. Conclusions: PBPM, conducted collaboratively by pharmacists and physicians, effectively optimized antibiotic use, reduced adverse event risks, shortened treatment duration, and lowered healthcare costs without compromising clinical outcomes. These findings support PBPM implementation to improve antibiotic stewardship in older patients with common infections. Clinical trial number: not applicable.