Investigation of risperidone oral solution administration practices and risk of beverage-related drug interactions in Japanese patients

Risperidone oral solution should not be administered in diluted form, as its active content may decrease when mixed with tea-extracted beverages. However, information regarding the actual administration practices among patients routinely using this medication remains unclear. In this study, we aimed to investigate the real-world administration practices of risperidone oral solution, with a focus on whether patients or medication administrators dilute the solution in beverages. A questionnaire survey was conducted among patients routinely using risperidone oral solution and their medication administrators who visited pharmacies in the Tohoku region of Japan. Overall, 22.6% of respondents reported occasionally mixing the solution with beverages. No significant difference was observed in the percentage of mixing with beverages between the brand-name and generic drugs. However, a significant age-related difference was noted: participants aged ≥ 60 years were more likely to mix the solution with beverages than those aged < 60 years. Tea and cola—beverages with which risperidone should not be mixed—were also identified among the responses. These findings highlight that the practice of mixing risperidone oral solution with inappropriate beverages is concerning and must be addressed. It is necessary to prevent the decline in risperidone content by gathering reliable drug information and offering personalized medication guidance.