Prevalence and disposal of unused medicines: a systematic review of cross-sectional studies

Abstract

Abstract Objectives We aimed to systematically review cross-sectional studies of unused medicines that described the prevalence, types of unused medicine, disposal practices and factors associated with unused medicines. Methods We searched Medline, EMBASE, CINAHL, Web of Science, Scopus, and Google Scholar. We identified and selected cross-sectional studies published between database inception and June 2023 examining the prevalence of unused medicines and factors associated with their disposal. Key findings We included 57 studies in the review. The prevalence of unused medicines ranged from 21.4% to 98.0% (mean = 63.8%). The top reason people had unused medicines was because their conditions improved (40.0%). The most common method to dispose of unused medicines was in the environment (66.9%), while a smaller percentage (12.9%) returned them to medicine take-back facilities. We found that there was a positive correlation between returning unused medicines and knowing how to dispose of them properly [(r(29) = 0.50, P = .006)]. However, actual disposal practice did not correlate with knowing about environmental risks [r(31) = −0.17, P = .4] or willingness to return the unused medicines [r(13) = 0.40, P = .20]. Conclusions The prevalence of unused medicines and their disposal methods vary between countries. Improper medicines cannot solely attributed to consumer knowledge about the risks and attitudes of consumers. More research is needed to understand the impact of legislation and the availability of medicine take-back facilities.