Analysis of the impact of national centralized volume-based procurement drug policy on the market dynamics of tuberculosis drugs

Background China's National Centralized Drug Procurement (NCDP) consolidates public-sector procurement demand and links guaranteed volumes to competitive tendering. The impact of this policy on reshaping the tuberculosis (TB) medicines market-specifically prices and expenditure, procurement volumes, and market structure-remains insufficiently quantified using time-series methods across multiple procurement cycles and hospital types. Methods A hospital-stratified interrupted time series (ITS) study was conducted utilizing monthly public-hospital procurement data from January 2015 to December 2022. Six TB medicines included in national procurement rounds 2-4 comprised the intervention group: isoniazid, moxifloxacin, ethambutol, linezolid, levofloxacin, and pyrazinamide. Nine TB-related medicines not included in these rounds served as comparators: rifampicin, rifapentine, rifabutin, streptomycin, protionamide, cycloserine, p-aminosalicylic acid sodium, bedaquiline, and clofazimine. Analyses were stratified by hospital type (general versus TB-specialized hospitals) and drug classification (first-line versus second-line agents). Outcome measures included procurement volume, total expenditure and cost per defined daily dose (DDDc), market concentration, and the number of active manufacturers in hospital procurement. Segmented regression analysis estimated immediate level and subsequent slope changes. Sensitivity analyses with alternative comparator specifications assessed robustness and parallel trends assumptions. Results Following NCDP implementation, hospital procurement costs for TB medicines declined substantially across both hospital types. In general hospitals, expenditure decreased significantly. DDDc reductions were dramatic: linezolid decreased from approximately 800 Renminbi (RMB) to below 100 RMB; moxifloxacin from 99 RMB to 20 RMB; levofloxacin from 24 RMB to 9 RMB. Similar patterns were observed in specialized hospitals. Market structure effects exhibited heterogeneity: first-line drugs showed increased concentration with declining manufacturer participation, while second-line drugs demonstrated expanded supplier participation and decreased Herfindahl-Hirschman Index (HHI). Sensitivity analyses confirmed robustness across alternative comparator specifications. Conclusions The NCDP achieved substantial price and expenditure reductions for TB medicines whilst inducing heterogeneous effects on market structure-increased concentration for first-line drugs but expanded supplier participation and decreased market concentration for second-line drugs. TB-specialized hospitals, with higher baseline concentration and fewer suppliers, face heightened supply chain vulnerability. Given NCDP's design-where hospitals independently select among winning suppliers and may procure non-winning products-policymakers should implement differentiated approaches: multi-winner tender designs to preserve supplier diversity for first-line drugs; strategic stockpiles and supplier qualification programs for specialized hospitals; and continued volume-price guarantees for second-line agents such as linezolid and moxifloxacin. Regular monitoring of market structure indicators across hospital types is essential to balance price efficiency with supply resilience. Clinical trial number Not applicable.