Impact of varenicline supply suspension on smoking cessation services in Japan's universal health insurance system.

We examined changes in smoking cessation service utilization and prescribing patterns under the universal health insurance system during the varenicline supply suspension in Japan. We analyzed publicly available aggregated data from the NDB Open Database, which covers more than 95% of all health insurance claims. Monthly claims for nicotine dependence management fees from April 2019 to March 2024 were evaluated using interrupted time-series analysis, and annual prescription trends for varenicline and nicotine patches were assessed. The varenicline supply suspension was associated with a significant immediate decline in service claims (-6443.5; 95% confidence interval: -8360.2 to -4526.9; p < 0.001). Claims showed a modest downward trend before the suspension, followed by a gradual increase thereafter. Varenicline use declined after 2021, accompanied by increased nicotine patch use. These findings indicate that the supply suspension disrupted smoking cessation services and altered prescribing patterns in Japan, highlighting vulnerability in systems with limited reimbursed therapies.