title: Drug-drug interactions associated with length of stay and cost of hospitalization.
abstract: OBJECTIVE
  To evaluate the prevalence of drug-drug interactions (DDI) in prescriptions of hospitalized patients and to identify risk factors associated.
  
  
  METHODS
  A retrospective cross-sectional analysis of prescription data and medical records from a public hospital in Brazil was conducted to identify potential DDI. An inappropriate drug combination was identified and classified with a standard drug interaction source. The main diagnoses were classified with Charlson Comorbidity Index (CCI). Sex, age, polypharmacy and length of stay, among other variables, were correlated with the frequency of potential DDI.
  
  
  RESULTS
  The study included 589 patients and 3,585 prescriptions. Thirty-seven percent of the patients were exposed to at least one potential interaction during their stay in the hospital. The most frequent interacting pair was Digoxin+Furosemide (11%). In univariate analysis, several variables were associated with DDI, including sex, age, number of prescribed drugs, length and cost of hospitalization and CCI. Multivariate analysis showed that the adjusted odds of being prescribed a potential DDI among patients in polypharmacy was almost five-fold that of patients taking less than five drugs. Further, length of stay, CCI and cost of hospitalization were independently associated with DDI.
  
  
  CONCLUSIONS
  Analysis of prescription data found that a substantial number of potential DDI were identified. Results of this study indicate that DDI is associated with number of prescribed drugs, increased duration of stay in the hospital and cost, which suggest that DDI are a significant clinical and economic problem. Potential damage to patients could be avoided.
authors.affiliation: Multidisciplinar Institute of Health, Federal University of Bahia, Vitória da Conquista, Brazil. cs_moura@yahoo.com.br
authors.forename: Cristiano Soares
authors.initials: CS
authors.lastname: Moura
authors.forename: Francisco Assis
authors.initials: FA
authors.lastname: Acurcio
authors.forename: Najara Oliveira
authors.initials: NO
authors.lastname: Belo
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging; D001938:Brazil; D003430:Cross-Sectional Studies; D004347:Drug Interactions; D011307:Drug Prescriptions / Q000706:statistics & numerical data*; D005260:Female; D017721:Hospital Costs / Q000706:statistics & numerical data*; D006786:Hospitals, Urban; D006801:Humans; D007902:Length of Stay / Q000706:statistics & numerical data*; D008297:Male; D008875:Middle Aged; D019338:Polypharmacy; D012189:Retrospective Studies; D012307:Risk Factors; D012727:Sex Characteristics; D055815:Young Adult