Real-World Experience with High- versus Low-Dose Polymyxin B for Pulmonary Infections: A Retrospective Cohort Study.

Background: Polymyxin B(PMB) is crucial for treating carbapenem-resistant Gram-negative pulmonary infections. Despite existing guidelines, real-world dosing varies widely. The clinical and economic outcomes associated with higher versus lower dose regimens in routine practice require further elucidation. Methods: This single-center retrospective cohort study included 235 adult patients with pulmonary infections who received intravenous PMB between January 2020 and December 2024. Based on real-world dosing practices, participants were categorized into high-dose and low-dose groups for comparative analysis of clinical efficacy, safety, and direct medical costs. Results: A statistically significant difference in 28-day and 42-day all-cause mortality was observed between the two groups, although no significant differences were detected in clinical response rates or hospital length of stay. Safety assessments showed no statistically significant differences in hepatotoxicity, nephrotoxicity, or hematologic toxicity between groups; however, most non-significant adverse events occurred more frequently in the high-dose group. Direct medical costs analysis showed that the low-dose regimen significantly reduced drug costs, although total hospitalization costs did not differ significantly between the two groups. Conclusion: For pulmonary infections, low-dose PMB (<1.5 mg/kg/day) combined with extended therapy was associated with lower mortality, better safety, and similar clinical response vs. high dose. Drug costs were lower, suggesting real-world cost savings. These findings support PMB dose optimization, but prospective validation is needed.