Objectives: Studies on the impacts of copayments for outpatient prescription drugs under Taiwan’s National Health Insurance are very limited. The aim of this study is to characterize those who received copayments for prescriptions at outpatient visits and compared them with their counterparts (the copayment-waving group) between 2008 and 2017 in Taiwan. Specifically, patients’ or physicians’ characteristics associated with copayments for prescriptions at outpatient visits were examined.

Methods: Using Taiwan’s National Insurance Research Database (NHIRD), we identified 70,611,877 outpatient prescriptions between 2008 and 2017.The proportion of copayment accounted for the total drug expenditures were calculated in prescriptions eligible for copayment, and exemptionscenarios were examined for copayment-waving prescriptions. The number of medications and days of supply per prescription as well as patients’ and physicians’ characteristics were also analyzed between prescriptions with and without copayment.

Results: Among all prescriptions identified, 85.2% of them were fully covered by the NHI. Even though patients paid out-of-pocket, 40.4% of prescriptions met the lowest tier of copayment (NTD $20 (=USD $0.72, currency rate on 1st January 2022)). The leading cause of copayment-waving was total drug expenditure not exceeding NTD $100 (=USD $3.61) (66.3%), followed by refillable prescriptions for chronic disease (17.9%). Formedical centers and regional hospitals, refillable prescriptions were the major cause of copayment exemptions (53.6% and 49.9%), while total drug expenditures not exceeding NTD $100 ranked first in district hospitals and clinics (47.3% and 82.8%). The average drug expenditures per prescriptions (with drug expenditures exceeding NTD $100) with or without drug copayment were $544.5 and $1081.1, respectively.

Conclusions: Our study provides a comprehensive overview of the impacts of outpatient drug copayment policy on several measures associated with healthcare utilization between 2008 and 2017 in Taiwan. These data could serve as a valueable reference for future policy implementation.