Frequency, causes, and duration of drug shortages in South Korea, 2018-2024: a nationwide descriptive analysis of regulatory reporting data and temporal patterns across the COVID-19 pandemic.

Background: Drug shortages threaten treatment continuity and health-system resilience, yet empirical evidence from South Korea remains limited. Methods: We conducted a nationwide, retrospective descriptive analysis of 868 drug products (1,054 shortage reports) officially reported to the Ministry of Food and Drug Safety (MFDS) between January 2018 and February 2024. Shortages were characterized by frequency, reported cause (six categories), and duration, and compared between reportable and non-reportable drugs. Duration analyses were restricted to 360 temporary supply disruptions. To examine COVID-19-related temporal patterns, temporary supply disruptions during 2018-2023 were grouped into pre-COVID-19 (2018-2019), COVID-19 (2020-2021), and later COVID-19 (2022-2023) periods, defined a priori around the WHO pandemic declaration. Continuous variables were summarized as median (interquartile range, IQR) and categorical variables as counts (%). Analyses were descriptive; no causal inference was intended. Results: A directly substitutable product with the same active ingredient, strength, and dosage form was available for only 269 of 868 drugs (31.0%). Cause structures differed by event type: internal supply issues predominated among temporary supply disruptions (183/396 cause attributions, 46.2%) and business decisions among permanent discontinuations (418/720, 58.1%). Among temporary supply disruptions, regulatory constraints showed the longest durations (median 104 days; IQR 63.3-328) and the largest share lasting ≥366 days (25.0%). Products with ≥2 reported drug shortages were more frequent among orphan drugs (23.3%) and withdrawal-prevention drugs (21.1%), whereas Korean essential drugs showed a widely dispersed duration distribution (median 48 days; IQR 29.8-233.8; 25.6% > 180 days). The numbers of temporary supply disruptions were 53, 106, and 178 in the pre-COVID-19, COVID-19, and later COVID-19/recovery periods, respectively. While internal supply issues remained the leading reported cause throughout (69.8%, 53.4%, and 39.5%), the relative contribution of raw-material supply disruptions (11.3%-26.7%) and increased demand (9.4%-23.1%) grew. Conclusion: The patterns observed are consistent with structural vulnerabilities related to market incentives, regulatory processes, and API import dependence, with raw-material and demand-related causes becoming more prominent in the later study periods. Potential policy responses, each requiring separate evaluation, include supply diversification, domestic API production, cost-compensation for economically vulnerable essential medicines, and a risk-based early-warning system with severity-tiered responses.