Time series analysis of the new tiering pricing policy for generic medicines in South Korea

Background: South Korea introduced a new tiered pricing policy for generic medicines in July 2020, linking reimbursement to bioequivalence testing and active pharmaceutical ingredient registration requirements. While the policy aimed to improve market efficiency and quality assurance, its impact on product availability and generic uptake has not been fully evaluated. Methods: A retrospective observational study was conducted using the National Health Insurance Drug Master File and claims data from January 2017 to December 2022, with descriptive analyses covering 2017-2022. Interrupted time series (ITS) analysis with segmented regression was applied to assess changes in the number of marketed medicines and the expenditure-based market share of generics following the policy intervention, including stratified analyses by Anatomical Therapeutic Chemical level-1 categories. This study estimated policy effects using expenditure-based indicators under the revised reimbursement framework. Results: The policy resulted in a significant immediate increase in the number of generic medicines (+1,811; p < 0.001), followed by a reversal in trend from a pre-policy monthly increase to a post-policy decline. No significant immediate change was observed in the expenditure-based market share of generics; however, a significant positive post-policy trend was identified (+0.08 percentage points per month; p < 0.001). Conclusion: South Korea's tiered pricing policy led to rapid structural adjustments in the generic medicines market, with substantial short-term increases in product registrations and gradual increases in generic expenditure share over time. By linking pricing to quality-related requirements, the policy may strengthen market competitiveness and quality compliance. Continued monitoring and class-specific complementary strategies are warranted to sustain long-term effectiveness.