Relationship between prices of fixed-dose and free-equivalent combination: a survey of medicines in China's National Reimbursement Drug List

Fixed-dose combinations (FDCs) may simplify treatment, but their prices relative to corresponding free-equivalent combinations (FECs) are not well characterized in China. This study described FDC-to-FEC price relationships in China’s National Reimbursement Drug List (NRDL) and examined associations with therapeutic area, formulary category, and volume-based procurement (VBP). This nationwide cross-sectional study included 63 FDC–FEC groups in the 2022 NRDL with price data in 2023. FEC component prices were adjusted to the FDC strength and dosage form under Chinese differential pricing rules; each FDC unit price was divided by the sum of adjusted FEC prices. Ratios were summarized using medians and interquartile ranges (IQRs), compared using Kruskal–Wallis and Wilcoxon rank-sum tests, and analyzed using a multivariable Gamma generalized linear model with a log link. The median ratio was 0.94 (IQR 0.55–1.44; range 0.18–3.34); 35 of 63 groups (55.56%) had ratios below 1. Ratios differed across the four therapeutic areas with at least five observations ( P < 0.001) and were lower for negotiation-catalog than regular-catalog FDCs (0.51 vs. 1.12; P < 0.001). Ratios were higher when at least one FEC component was included in VBP (1.12 vs. 0.63; P = 0.003). In the adjusted analysis of 48 groups, therapeutic area remained associated with the ratio ( P = 0.023), negotiation-catalog FDCs had lower ratios than regular-catalog FDCs ( P < 0.001), and VBP status was not independently associated ( P = 0.431). Among reimbursed FDCs with identifiable comparators and price data, product-level price relationships varied by therapeutic area and formulary category. The unadjusted VBP difference did not persist after adjustment. These unit-price ratios describe existing price relationships and may inform future reimbursement decisions.