Unfilled Prescriptions in Japan: A 10‐Year Retrospective Analysis

Purpose To describe primary medication non‐adherence (PMN; failure to fill newly prescribed medications) patterns in Japan over a decade under universal healthcare coverage. Methods We conducted a retrospective cohort study using the DeSC Healthcare database, which integrates pharmacy dispensing records with Japanese medical claims data. We analyzed medical claims with prescription fees from April 2014 to September 2023. PMN was defined as the absence of a pharmacy dispensing record following a documented prescription issuance. Results We analyzed 2 620 639 medical claims from 1 935 948 unique patients. The overall PMN proportion was 4.9%, with 5.6% in 2014 and 4.3% in 2023. Age‐specific subgroup analysis showed proportions ranging from 4.5% to 5.2%. Across all 7 days of the week, proportions ranged from 4.9% to 5.1%. Disease‐specific analysis showed proportions ranging from 4.0% (hypertension) to 7.0% (spinal disorders). Conclusions PMN remained around 5% over the study period. Health insurers should consider developing notification mechanisms to alert healthcare providers about unfilled prescriptions. Future research should evaluate the impact of electronic prescribing systems.