Determining Korean Defined Daily Dose (KDDD) of Anti-cancer and Antihypertensive Drugs Using Modified-Delphi Methods

Background: World Health Organization (WHO) Defined Daily Dose (DDD) often mismatches Korean clinical practice for anticancer (L01) and antihypertensive (C02-C09) drugs, causing statistical distortion in drug utilization research (DUR).This study aimed to establish Korean DDD (KDDD) for these agents.Methods: A modified Delphi method was employed.An expert panel (n=13) of clinicians and pharmacists reviewed 26 anticancer and 16 antihypertensive ingredients lacking a WHO DDD or showing significant discrepancies.KDDD proposals were drafted based on WHO guidelines, domestic approvals, and Health Insurance Review and Assessment Service (HIRA) claim data on prescribed daily dose (PDD) distributions.Two survey rounds were conducted to achieve consensus.Consensus-based KDDDs were determined for all 42 ingredients.Results: For anticancer drugs, KDDDs were assigned based on single approved doses (n=16), most frequent doses (e.g., imatinib), indication-specific average doses (e.g., axitinib), or doses adjusted for drug-holiday cycles (e.g., palbociclib).For antihypertensives, KDDDs were based on single doses (n=5), average range doses (n=6), or doses for major domestic indications (n=5).These KDDDs enabled, for the first time, standardized consumption measurement (DDD/1,000 inhabitants/day, DID) for 26 anticancer agents previously unquantifiable under WHO DDD.The 26 newly assigned anticancer KDDDs accounted for 36.4% of total anticancer expenditure (USD 430.8 million) in 2019, highlighting their substantial fiscal impact and the urgency of accurate utilization monitoring.Conclusion: This study established robust, evidence-based KDDDs reflecting Korean clinical reality through a systematic Delphi consensus.These KDDDs provide an essential tool for accurate DUR and rational health policy, particularly for monitoring high-cost oncology drugs.