Safety concerns in simultaneous use of prescription and 'over-the-counter' medicines- results of patient survey in Estonia.

During the last decades, the share of population using prescription (Rx) medicines has considerably increased. With the wider introduction of self-medication and the use of over-the-counter (OTC) medicines, there is a real threat for drug-drug interactions between Rx and OTC medicines neither identified nor overseen by healthcare specialists. The objectives of this survey were to ascertain how often, and for what conditions OTC and Rx medicines are used simultaneously, and to discuss possible health hazards connected with the concomitant use of these medicines. This survey was designed as a descriptive, cross-sectional questionnaire-based interview which was conducted amongst pharmacy customers and patients in urban and rural areas of Estonia in between 2010-2012. In total, 712 respondents participated in the survey. Of those, 50.4% reported concomitant use of Rx and OTC medicines during the survey. The simultaneous use of Rx and OTC medicines increased with age and the number of chronic diseases (both p < 0.001). Of chronic patients, 37.1% used Rx and OTC medicines on a daily basis over a four-week period before the survey, and considering reported chronic diseases and the most widespread OTC medicines, they could encounter drug-drug interactions between Rx medicines (e.g. antihypertensives, anti-inflammatory medicines) and OTC medicines (e.g. paracetamol, NSAID-s, herbal medicines and adsorbents). The present survey revealed frequent concomitant use of Rx and OTC medicines. Especially vulnerable are chronic and elderly patients. In the future, both patients and healthcare specialists should pay more attention to possible drug-drug interactions of Rx and OTC medicines.