Mechanisms influencing generic drug substitution behavior under the national centralized drug procurement policy.

Background: As a key component of China's healthcare reform, the national centralized drug procurement (NCDP) policy has significantly influenced physician behavior regarding generic substitution. Therefore, it is essential to investigate the mechanisms underlying physicians' decisions to prescribe bid-winning generics under the NCDP, to provide empirical evidence for policy optimization, and to support the broader implementation of generic substitution strategies. Methods: Drawing upon the theory of planned behavior (TPB), a conceptual model was developed, and a corresponding scale was constructed. Structural equation modelling (SEM) was employed to examine the influencing mechanisms, focusing on the relationships among subjective attitude, subjective norms, perceived behavioral control, subjective willingness, and actual prescribing behavior. Results: The findings indicated that subjective attitude was the primary driver of physicians' intentions to prescribe bid-winning generics. Subjective norms did not exert a statistically significant effect on prescribing willingness, while perceived behavioral control was found to have a negative influence on intention and minimal impact on actual substitution behavior. Subjective willingness has emerged as a critical mediating factor that directly shapes physicians' substitution behavior. Conclusion: This study highlights the importance of enhancing physicians' positive attitudes towards bid-winning generics, fostering a supportive normative environment, and mitigating excessive perceived behavioral control. These strategies may strengthen prescribing intentions, support effective and sustainable implementation of the NCDP, promote generic substitution, and reduce patients' medication costs.