title: Risk of potential drug-drug interactions among Brazilian elderly: a population-based, cross-sectional study.
abstract: BACKGROUND
  Drug-drug interactions (DDIs) are one of the main causes of adverse reactions related to medications, being responsible for up to 23% of hospital admissions. However, only a few studies have evaluated this problem in elderly Brazilians.
  
  
  OBJECTIVE
  To determine the prevalence of potential DDIs (PDDIs) in community-dwelling elderly people in Brazil, analyse these interactions with regard to severity and clinical implications, and identify associated factors.
  
  
  METHODS
  A population-based cross-sectional study was carried out involving 2143 elderly (aged >or=60 years) residents of the metropolitan area of Sao Paulo, Brazil. Data were obtained from the SABE (Saúde, Bem estar e Envelhecimento [Health, Well-Being, and Aging]) survey, which is a multicentre study carried out in seven countries of Latin America and the Caribbean, coordinated by the Pan-American Health Organization. PDDIs were analysed using a computerized program and categorized according to level of severity, onset, mechanism and documentation in the literature. The STATA software statistical package was used for data analysis, and logistic regression was conducted to determine whether variables were associated with PDDIs.
  
  
  RESULTS
  Analysis revealed that 568 (26.5%) of the elderly population included in the study were taking medications that could lead to a DDI. Almost two-thirds (64.4%) of the elderly population exposed to PDDIs were women, 50.7% were aged >or=75 years, 71.7% reported having fair or poor health and 65.8% took 2-5 medications. A total of 125 different PDDIs were identified; the treatment combination of an ACE inhibitor with a thiazide or loop diuretic (associated with hypotension) was the most frequent cause of PDDIs (n = 322 patients; 56.7% of individuals with PDDIs). Analysis of the PDDIs revealed that 70.4% were of moderate severity, 64.8% were supported by good quality evidence and 56.8% were considered of delayed onset. The multivariate analysis showed that the risk of a PDDI was significantly increased among elderly individuals using six or more medications (odds ratio [OR] 3.37) and in patients with hypertension (OR 2.56), diabetes mellitus (OR 1.73) or heart problems (OR 3.36).
  
  
  CONCLUSIONS
  Approximately one-quarter of the elderly population living in Sao Paulo could be taking two or more potentially interacting medicines. Polypharmacy predisposes elderly individuals to PDDIs. More than half of these drug combinations (57.6%, n = 72) were part of commonly employed treatment regimens and may be responsible for adverse reactions that compromise the safety of elderly individuals, especially at home. Educational initiatives are needed to avoid unnecessary risks.
authors.affiliation: Nursing College, University of São Paulo, São Paulo, Brazil.
authors.forename: Silvia-Regina
authors.initials: SR
authors.lastname: Secoli
authors.forename: Albert
authors.initials: A
authors.lastname: Figueras
authors.forename: Maria Lúcia
authors.initials: ML
authors.lastname: Lebrão
authors.forename: Fernão Dias
authors.initials: FD
authors.lastname: de Lima
authors.forename: Jair Licio Ferreira
authors.initials: JL
authors.lastname: Santos
mesh_terms: D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000009:adverse effects / Q000627:therapeutic use; D001938:Brazil / Q000453:epidemiology; D003430:Cross-Sectional Studies; D004347:Drug Interactions; D004359:Drug Therapy, Combination; D017723:Drug Utilization Review; D064420:Drug-Related Side Effects and Adverse Reactions; D005260:Female; D006801:Humans; D008297:Male; D019338:Polypharmacy; D015995:Prevalence; D018570:Risk Assessment; D012307:Risk Factors; D049993:Sodium Chloride Symporter Inhibitors / Q000009:adverse effects / Q000627:therapeutic use; D049994:Sodium Potassium Chloride Symporter Inhibitors / Q000009:adverse effects / Q000627:therapeutic use
chemical_list: D000806:Angiotensin-Converting Enzyme Inhibitors; D049993:Sodium Chloride Symporter Inhibitors; D049994:Sodium Potassium Chloride Symporter Inhibitors
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