Impact of Volume-Based Drug Procurement Policy on Drug Use Structure of Chinese Public Medical Institutions: A Difference-in-Difference Analysis of Nine Pilot Cities and Twelve Non-pilot Provinces

Background: In 2019, the Chinese government implemented the first round pilot of volume-based drug procurement in 4 municipalities and 7 sub-provincial cities, i.e. “4+7” policy. This study evaluated the impact of “4+7” policy on the use structure of policy-related drugs. Methods Data of China Drug Supply Information Platform (CDSIP) database was used, covering 18,636 public medical institutions from 9 pilot cities and 12 non-pilot provinces in mainland China. “4+7” policy-related drugs were selected as study samples, including 25 drugs in the “4+7” procurement List and 83 alternative drugs that have an alternative relationship with “4+7” List drugs. “4+7” List drugs were divided into bid-winning and bid-non-winning products. Drug Structure Index (DSI) was employed as the outcome variable, and higher DSI refers to the use proportion of higher-DDDc (Defined Daily Drug cost) drugs increased. Difference-in-difference (DID) method was employed to estimate the net effect of “4+7” policy. Results After policy intervention, the DSI of bid-winning drugs significantly decreased ( β =-0.233, p <0.0001), while non-winning drugs ( β  = 0.177, p <0.001) and “4+7” List drugs ( β  = 0.050, p 0.05), while a remarkable increase was found in primary healthcare settings ( β  = 0.033, p <0.05). In three post-“4+7” periods, the increments of DSI for non-winning products were 17.54% (period 1), 18.35% (period 2), and 19.66% (period 3). The DSI of “4+7” List drugs significantly increased in post-“4+7” period 2 and 3 (all p -values<0.05). Conclusions The use proportion of higher-DDDc bid-winning drugs significantly decreased after policy intervention. However, among drugs not involved by NCDP policy, the use proportion of higher-DDDc drugs significantly increased after policy intervention, moreover, the increment was more pronounced at the later periods of policy implementation. The clinical use monitoring and the physician’s prescription behavior supervision should be strengthened.