Use of over-the-counter-like drugs among adults with indicated chronic diseases: A nationwide descriptive study in Japan

IntroductionThe Japanese Ministry of Health, Labour, and Welfare proposed increased copayments for over-the-counter (OTC)-like drugs, with possible special consideration for certain chronic diseases, although the specific diseases to be included were not clarified as of January 2026. The costs attributable to OTC-like drugs indicated for chronic diseases in adults remain unclear. MethodsUsing the DeSC database (individual-level claims data) in fiscal year 2023, we estimated the average per-person annual costs of the study OTC-like drugs indicated for adults with representative chronic diseases. The estimates were stratified by sex and age. We also computed the national estimates of the numbers of adults with representative chronic diseases who would need OTC-like drugs and the costs attributable to these drugs by applying stratum-specific estimates from the DeSC database to national population counts and aggregated claims data from the National Database of Health Insurance Claims Open Data. The study OTC-like drugs included oral acetaminophen, oral nonsteroidal anti-inflammatory drugs (NSAIDs), topical anti-inflammatory patches, oral second-generation antihistamines, and heparinoid-containing topical preparations. ResultsThe average per-person annual costs were several hundred yen for acetaminophen and several thousand yen for the other drug categories, with marked variation by drug category, chronic disease, age, and sex. In the national estimates, the proportion of OTC-like drug users with representative chronic diseases was <10% in every disease-age-sex stratum; nevertheless, the maximum stratum-specific shares of total OTC-like drug costs attributable to these groups were high (up to 50-60% for osteoarthritis for acetaminophen/NSAIDs/patches and up to [~]60% for atopic dermatitis/asteatosis for heparinoids). ConclusionsThe average per-person annual costs for OTC-like drugs varied substantially across drug categories and patient subgroups. Indicated chronic diseases in adults may account for substantial OTC-like drug costs within some strata, despite representing a small fraction of users.