Analysis of the drug interactions associated to domiciliary drug therapy in elderly hospitalized patients

To determine the prevalence of potentially relevant drug-drug interactions associated with chronic treatment of elderly patients over 64-years of age on hospital admission and the factors associated with an increased presence of these. Cross-sectional observational study in a hospital referral area. All patients aged 65 or over admitted to the hospital in the last three months in 2009 were included. Based on the drug database of the General Council of Colleges of Pharmacy (BOT), drug-drug interactions and their potential clinical relevance were identified. To identify the variables associated with a higher prevalence of drug-drug interactions, analyses of correlation and of univariable linear regression and uni-and multivariable logistic regression analyses were performed using the SPSS, version 15.0. We analyzed the drug prescription data of 382 patients, whose mean age was 7.7 years. A total of 45.3% of patients had comorbidities and 78.8% had taken 5 or more drugs. We identified 272 clinically relevant drug-drug interactions that involved 159 patients (41.6%). Seven pharmacological groups accounted for 80.6% of the drug-drug interactions. The variables that had a statistically significant association to a higher prevalence of relevant interactions were polypharmacy, respiratory insufficiency, and treatment with proton-pump inhibitors, vitamin K antagonists, diuretics or anti-platelet drugs. A high prevalence of relevant drug-drug interactions was found in elderly hospitalized patients. Our findings suggest that prevention strategies should be implemented to avoid their associated adverse events, especially in high risk populations.