Background Over-the-counter (OTC) medicines are typically safe. However, there is evidence that OTC medicines can sometimes cause harm as a result of their misuse, abuse and dependence. Aim of the review To review the literature on OTC medicines misuse, abuse and dependence in adults and identify the implicated medicines, contributing factors, associated harms and risk-mitigating interventions. Methods Following PRISMA guidelines, electronic databases including Cumulative Index to Nursing and Allied Health Literature (CINAHL), EMBASE, MEDLINE, PsycINFO Web of Science and Google Scholar were searched for peer-reviewed journal articles published in English between January 2011 and March 2019. Quantitative, qualitative and mixed-methods studies assessing aspects of misuse, abuse and dependence of OTC medicines in individuals aged 18 years or more were included. Studies that solely focused on adolescents only, doping in sports or abuse of OTC medicines in people who are substance abusers were excluded. The random effect meta-analysis model was used to pool the prevalence among the population-based studies. Results Of 2355 peer-reviewed studies initially identified, 53 were included in this review. According to the study design, the prevalence varied, but the overall pooled prevalence in the population-based studies was: 16.2% for misuse, 2.0% for abuse, and 7.2% for dependence. The common OTC medicines groups involved in the problematic use were analgesics (with or without codeine), sedative antihistamines, cough mixtures containing dextromethorphan. Physical, psychological, social and financial harms were associated with problematic use of OTC medicines in addition to hospitalisation and death. Interventions for the affected individuals were provided mainly through the community pharmacies, general practices and specialised addiction centres. Conclusion The problematic use of OTC medicines is quite prevalent in adults, necessitating raising public awareness about their safe use. In addition, innovative harm minimisation models need to be developed, evaluated and implemented across health care settings.
