Impact of a local formulary on prescribing patterns and pharmaceutical expenditure: an observational study in Japan.

BACKGROUND: The implementation of local formularies in Japan began in November 2018 in the Sakata area of Yamagata Prefecture. A local formulary is a regional list of recommended pharmaceuticals selected based on comprehensive criteria, including efficacy, safety, and economic considerations. However, the economic impact of these formulations has not yet been clearly demonstrated. This retrospective observational study aimed to verify their effectiveness by analyzing real-world data. METHODS: Prescription and outpatient data from the National Database were extracted for October 2018, 2019, and 2020, covering both the Sakata area and the rest of Yamagata Prefecture. The number of prescriptions and cost per prescription were calculated for four therapeutic classes: proton pump inhibitors/potassium-competitive acid blockers, angiotensin receptor blockers, α-glucosidase inhibitors, and statins. RESULTS: In 2020, the formulary adherence rate in Sakata exceeded that in the rest of Yamagata Prefecture across all therapeutic classes. Although the cost per prescription annually decreased in Sakata, some therapeutic classes showed increased costs in the remainder of the prefecture from 2019 to 2020. In contrast, formulary adherence to outpatient medical prescriptions was lower in Sakata, and no clear impact of the local formulary was observed. Applying the rate of cost reduction observed in Sakata to the rest of the prefecture, the estimated monthly savings reached approximately 35 million JPY after 1 year and 15 million JPY after 2 years. Furthermore, although no prior measures existed to control the use of originator drugs without generics, Sakata showed a trend of reduced usage compared with the rest of the prefecture, suggesting the influence of the local formulary. CONCLUSIONS: Local formularies can contribute to the sustainability of Japan's healthcare financing systems.