title: Drug-drug interactions in a cohort of hospitalized elderly patients.
abstract: OBJECTIVE
  The aim of this study is to assess the prevalence of patients exposed to potentially severe drug-drug interactions (DDIs) at hospital admission and discharge and the related risk of in-hospital mortality and adverse clinical events, readmission, and all-cause mortality at 3 months.
  
  
  METHODS
  This cross-sectional, prospective study was held in 70 Italian internal medicine and geriatric wards. Potentially severe DDIs at hospital admission and discharge; risk of in-hospital mortality and of adverse clinical events, readmission, and all-cause mortality at 3-month follow-up.
  
  
  RESULTS
  Among 2712 patients aged 65 years or older recruited at hospital admission, 1642 (60.5%) were exposed to at least one potential DDI and 512 (18.9%) to at least one potentially severe DDI. Among 2314 patients discharged, 1598 (69.1%) were exposed to at least one potential DDI and 1561 (24.2%) to at least one potentially severe DDI. Multivariate analysis found a significant association with an increased risk of mortality at 3 months in patients exposed to at least two potentially severe DDIs (Odds ratio 2.62; 95% confidence interval, 1.00-6.68; p = 0.05). Adverse clinical events were potentially related to severe DDIs in two patients who died in the hospital, in five readmitted, and one who died at 3 months after discharge.
  
  
  CONCLUSIONS
  Hospitalization was associated with an increase in potentially severe DDIs. A significant association was found for mortality at 3 months after discharge in patients with at least two potentially severe DDIs. Careful monitoring for potentially severe DDIs, especially those created at discharge or recently generated, is important to minimize the risk of harm.
authors.affiliation: Laboratory for Quality Assessment of Geriatric Therapies and Services, Drug Information Service for the Elderly, Istituto di Ricerche Farmacologiche Mario Negri (IRCCS), Milan, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Pasina
authors.forename: Codjo D
authors.initials: CD
authors.lastname: Djade
authors.forename: Alessandro
authors.initials: A
authors.lastname: Nobili
authors.forename: Mauro
authors.initials: M
authors.lastname: Tettamanti
authors.forename: Carlotta
authors.initials: C
authors.lastname: Franchi
authors.forename: Francesco
authors.initials: F
authors.lastname: Salerno
authors.forename: Salvatore
authors.initials: S
authors.lastname: Corrao
authors.forename: Alessandra
authors.initials: A
authors.lastname: Marengoni
authors.forename: Alfonso
authors.initials: A
authors.lastname: Iorio
authors.forename: Maura
authors.initials: M
authors.lastname: Marcucci
authors.forename: Piermannuccio
authors.initials: P
authors.lastname: Mannucci
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D004347:Drug Interactions; D064420:Drug-Related Side Effects and Adverse Reactions / Q000401:mortality; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D007558:Italy; D008297:Male; D015999:Multivariate Analysis; D019338:Polypharmacy
keywords: aged; drug interactions; hospitalization; mortality; pharmacoepidemiology