Changes in Oral Analgesic Prescribing in Japan between Fiscal Year 2014 and Fiscal Year 2022: A Nationwide Analysis Using Open Data from the National Database of Health Insurance Claims and Specific Health Checkups of Japan.

INTRODUCTION: Nonsteroidal anti-inflammatory drugs (NSAIDs) have traditionally been central to pharmacological pain management in Japan, but population aging and increased use of mechanism-based analgesics may be changing prescribing patterns. We compared oral analgesic prescribing between fiscal year (FY) 2014 and FY2022 using nationwide claims-based open data, focusing on age and sex differences. METHODS: We analyzed aggregated prescription volumes from the 1st and 9th editions of the National Database of Health Insurance Claims and Specific Health Checkups of Japan Open Data for FY2014 (April 2014-March 2015) and FY2022 (April 2022-March 2023). Analgesics were grouped as acetaminophen, NSAIDs, cyclooxygenase-2 selective inhibitors, weak opioids, duloxetine, neuropathic pain medications, and neurotropin. We calculated population-based prescription volume rates (per 1,000 population) using official population estimates and summarized patterns by sex and age group (<20, 20-64, ≥65 years). We also calculated within-age-group composition (percent share). Poisson regression with log(population) offset estimated incidence rate ratios (IRRs) comparing FY2022 versus FY2014 using robust standard errors; NSAID IRRs were further examined by age-sex strata. RESULTS: Total prescription volume increased from 3.69 × 109 in FY2014 to 6.09 × 109 in FY2022. Rates per 1,000 population increased in all age groups, with the largest absolute increase among adults aged ≥65 years. NSAIDs remained the most frequently prescribed class by rate in adults aged 20-64 years, but composition shifted away from NSAIDs toward acetaminophen and neuropathic pain medications, most notably in older adults. Overall IRR was 1.55, with large increases for acetaminophen (2.51), neuropathic pain medications (2.14), duloxetine (2.29), and weak opioids (1.88), while NSAIDs changed modestly (1.15). NSAID rates decreased in older female strata (IRR <1 from ages 70-74 years). CONCLUSIONS: Oral analgesic prescribing in Japan increased substantially between FY2014 and FY2022, alongside age-specific shifts away from NSAIDs toward acetaminophen and neuropathic pain medications, particularly among older adults.