Therapeutic duplicate prescribing in Korean ambulatory care settings using the National Health Insurance claim data

Background Duplicate prescribing is known to occur across health systems and is one of the most frequent drug related problems. Therapeutic duplication (TD) increases the risk of adverse drug reactions without additional therapeutic benefits. Objectives This study aimed to develop TD criteria concerning four drug categories which are acid-related disorder drugs, antimicrobials, antihypertensives, and lipid modifying drugs and to estimate the prevalence of therapeutic duplicate prescribing at the ambulatory care settings in Korea. Methods TD criteria were developed using the WHO anatomical therapeutic chemical classification and modified with an expert consensus panel using the Delphi method. The prevalence of TD including ingredient duplication (ID) of four drug categories was examined using National Health Insurance claim database including 15 million patients during one month in 2009 (December). TD was defined as prescribing medications within the same category in the developed TD criteria list. Results The numbers of patients who received acid-related disorder drugs, antimicrobials, antihypertensives, and lipid-modifying drugs in the study period were 10,049,292, 7,584,131, 4,349,945, and 1,425,292 respectively. In the field of acid-related disorder drugs prescribed, there were 0.3 % IDs and 2.5 % TDs within a prescription issued by one prescriber. There were 8.4 % IDs and 14.5 % TDs between prescriptions issued at different ambulatory visits. In the field of antimicrobial medicines, there were 0.1 % IDs and 2.6 % TDs within a prescription, while there were 5.0 % IDs and 7.6 % TDs between different prescriptions. Amongst the antihypertensives prescribed, there were 0.4 % IDs and 1.9 % TDs within a prescription, while there were 9.9 % IDs and 11.5 % TDs between prescriptions. Lastly, looking at lipid-modifying drugs prescribed, there were 0.3 % IDs and 0.5 % TDs within one prescription, while there were 8.9 % IDs and 9.4 % TDs between prescriptions. Conclusion The prevalence of duplicate prescribing was substantial in the ambulatory care setting which is to be improved using the TD criteria developed from this study in the national drug utilization review system in Korea.