Prefectural Adequacy of Opioid Availability for Cancer Pain and Its Determinants in Japan: A Preliminary Study

INTRODUCTION: Opioid analgesics are the mainstay of cancer pain management. The annual opioid consumption globally indicates adequate opioid availability and the quality of palliative care. We investigated the current situation regarding the adequacy of opioid availability in individual prefectures in Japan and explored the determinants of adequacy. METHODS: We analyzed nationwide databases open to public inspection depicting the current Japanese healthcare situation. Opioid consumption for cancer pain was estimated from oxycodone and morphine data in the nationwide database. On the basis of the World Health Organization recommendations, we calculated adequacy based on the annual cancer deaths in each prefecture in 2013 and 2015. We investigated the associations between adequacy and either outpatient medical expenditure for hypertension and diabetes as a proxy of primary care practice or ratios of these risk holders in community. Outpatient medical expenditures for musculoskeletal disorders and neoplasms were also investigated. RESULTS: The nationwide adequacy of opioid availability was approximately 75%. The largest gaps in adequacy between prefectures were more than 65%. The adequacy correlated with expenditure but not local volumes of hypertension and diabetes in both years. The other two expenditures did not relate to opioid availability. CONCLUSIONS: Although precise data are required, our preliminary findings indicate that primary care practice is the key regulator of adequate opioid availability. Opioid adequacy in Japan is thus delayed in matching the global standard, and gaps in opioid adequacy among prefectures should be bridged rapidly to expand universal access to effective palliative care and cancer pain relief.