Antidiabetic Drug Use and Expenditure Trends After National Volume-Based Procurement Policy in Nanjing City: An Interrupted Time-Series Analysis.

Abstract

Aim: To evaluate the impact of China's National Volume-Based Procurement policy (NVBP) on utilisation and expenditures of antidiabetic drugs, with a focus on insulin, using real-world data from Nanjing.

Methods: Monthly procurement data from public healthcare facilities in Nanjing were analysed from January 2016 to December 2022. Drug utilisation was measured using the Anatomical Therapeutic Chemical/defined daily dose (ATC/DDD) methodology, and expenditures were measured by total spending and defined daily dose cost (DDDc). Linear regression analysis was employed to assess temporal trends, while interrupted time series (ITS) analysis was conducted to evaluate the impact of five policy implementation batches between January 2019 and December 2022 on changes in drug use and spending.

Results: During the 7-year study period, the use of NVBP-related antidiabetic drugs in Nanjing increased significantly, while total expenditures decreased. Before NVBP, expenditures grew annually by 9.1%, but declined by 12.4% per year after policy implementation. Insulin remained the dominant therapy but its utilisation proportion declined by approximately 40%, while metformin and sulfonylurea use increased. Newer antidiabetic drugs saw breakthrough growth post-policy. ITS analyses showed substantial immediate reductions in DDDc across batches, particularly for insulin, with unit costs decreasing by 36.5%. Utilisation responses varied by procurement batch, while domestic insulin products gained market share.

Conclusions: The NVBP was associated with substantial reductions in antidiabetic medicine costs and changes in market structure, while utilisation effects varied across procurement batches. The insulin-focused sixth batch achieved marked price reductions and increased substitution towards domestically produced insulin without increasing overall utilisation. These findings suggest that centralised procurement may improve affordability while reshaping pharmaceutical markets.