Impact of national volume-based procurement on physicians’ antimicrobial prescribing behaviours: an interrupted time series analysis of 1200 prescriptions in a tertiary hospital

Objective This study aimed to investigate the impact of the National Volume-Based Procurement (NVBP) policy on antimicrobial use intensity, prescribing structure, and medical costs among inpatients in a tertiary hospital in China.Methods This study retrospectively extracted 1200 inpatient prescriptions from a tertiary hospital between April 2019 and March 2024. Using interrupted time series (ITS) analysis, the study assessed the immediate-level changes and long-term trend effects of the NVBP policy on medication indicators such as defined daily doses (DDDs) and costs.Results Following NVBP implementation, antimicrobial prescribing structure changed significantly, with β-lactam utilization decreasing by 13.85%. The combination rate of β-lactams + fluoroquinolones fell significantly by 75.93%, while overall combination therapy remained unchanged. Use of special-grade antimicrobials showed a numerical increase (+31.98%), although not statistically significant. Cost indicators decreased significantly following policy implementation. ITS analysis further revealed a significant immediate decrease in the proportion of DDDs for NVBP antimicrobial agents (β2 = −15.464 units, p = 0.009), followed by a sustained upward trend (β3 = 1.400/month, p < 0.001). Similarly, DDDs of NVBP antimicrobial agents showed a significant upward trend (β3 = 0.135 units/month, p = 0.017) after the policy.Conclusion This study demonstrates that while the NVBP policy significantly reduced patient drug expenditures and promoted the use of NVBP varieties and nonrestricted antimicrobial agents, it also increased the proportion of special-grade antimicrobials agents, suggesting the need for caution against potential antimicrobial resistance and strengthened supervision of prescription.