Prevalence of potentially harmful drug interactions in older people in Australian aged-care facilities

Background: Older people living in aged-care facilities are prescribed more medications than those living in their own homes. Thus, increasing their risk of potentially harmful drug interactions. Few studies have investigated potential drug interactions in residents of aged-care facilities. Aim: To determine the prevalence of potentially harmful drug interactions in long-term residents of aged-care facilities. Method: Potentially harmful drug interactions were investigated using dispensing data from residents of 26 aged-care facilities who received one or more medications from July 2008 to June 2010. Drug interactions analysed were chosen based on their inclusion at the highest severity rating in at least 3 of 4 international drug information resources. Data were compared to findings from a cohort of Australian veterans. Results: Potentially harmful drug interactions were identified for 6.1% of the 3876 residents included in the study. A substantially higher incidence than previously reported in Australian veterans (1.5%) and certain overseas populations. Interactions involving warfarin, amiodarone, verapamil, lithium and methotrexate had the highest prevalence in aged-care residents, and generally a higher prevalence than in the Australian veteran population. Conclusion: Potentially harmful drug interactions were more prevalent in aged-care residents than in an Australian veteran population.