Background and Objectives: A new oral antidiabetic drug class, sodium-glucose co-transporter-2 inhibitors (SGLT-2 inhibitors), has been covered by national health insurance in Taiwan since May 2016. This study estimated the impacts of insurance coverage for SGLT-2 inhibitors on the replacement effects of antidiabetic drug use and the overall budget for antidiabetic drugs in Taiwan. Methods: Antidiabetic drugs were divided into nine categories based on the American Diabetes Association guidelines. We retrieved claims data from 2015 to 2017 for all patients diagnosed with diabetes mellitus from the National Health Insurance Research Database. An interrupted time series design and segmented regression were used to estimate the budget impact of insurance coverage for SGLT-2 inhibitors. Three scenarios were designed for the prescribing pattern for SGLT-2 inhibitors: (1) monotherapy, (2) metformin-based (m-based) drug prescriptions, and (3) metformin and sulfonylurea-based (m-s-based) drug prescriptions. Results: From May 2016 to April 2017, the prescription rate for m-based SGLT-2 inhibitors increased from 0.43 to 3.50%, and the expenditure rate increased from 0.82 to 6.58%. We found that the prescription rates of m-based and m-s-based dipeptidyl peptidase-4 inhibitors (DPP-4 inhibitors) decreased by 6.23 and 11.51% following the initiation of insurance coverage for SGLT-2 inhibitors, respectively. Furthermore, there was a 5.95% increase in the overall budget impact of antidiabetic drugs 1 year following the initiation of insurance coverage for SGLT-2 inhibitors. Conclusions: Both the prescription rates and expenditure rates for SGLT-2 inhibitors have increased since they have been covered by national health insurance in Taiwan, which significantly reduced usage of DPP-4 inhibitors but caused the positive growth of overall antidiabetic drug expenditures.
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