Clinical Drug Investigation

, Volume 31, Issue 5, pp 309–316 | Cite as

Potential Drug-Drug Interactions Associated with Prolonged Stays in the Intensive Care Unit

A Retrospective Cohort Study
  • Cristiano MouraEmail author
  • Nília Prado
  • Francisco Acurcio
Original Research Article


Background and Objectives: Drug-drug interactions (DDIs) are one cause of adverse drug events and can cause harm to hospitalized patients. Little has been done to study the relationship between potential DDIs and an increased length of stay (LOS) in the intensive care unit (ICU). The aim of this study was to determine the frequency of potential DDIs during ICU stays and to determine whether the frequency of these adverse events was associated with ICU LOS.

Methods: This retrospective cohort study was conducted from January to December 2007 in the ICU of the General Hospital of Vitória da Conquista, Brazil. The study population comprised all patients aged >18 years admitted to the hospital’s ICU. Demographic and prescription data were collected from medical files. All prescriptions administered during the period were examined. Potential DDIs were identified and classified according to the book Drug Interaction Facts. The median LOS was determined by the Kaplan-Meier method and Cox proportional hazards models were fitted to analyse the relationship between potential DDIs and the LOS.

Results: The study population comprised 236 adults, 158 (67%) of them men, between the ages of 18 and 96 years, with a mean ± SD age of 50 ± 20 years. The median LOS among patients with at least one DDI was 12 days compared with 5 days among those with no DDIs (p<0.01). Multiple Cox proportional regression analyses showed that a prolonged ICU stay was positively associated with DDIs (hazard ratio [HR] 0.54; 95% CI 0.37, 0.80; p<0.01), where an HR <1 indicates a variable that increases the risk of prolonged stay (i.e. an adverse outcome). This association was true even after controlling for the cost of hospitalization, the number of procedures and the number of prescribed drugs.

Conclusion: In this study, DDIs were found to be associated with a longer ICU stay. Given that LOS is an important indicator of the quality of health care delivered and that DDIs are considered avoidable, specific measures are necessary to increase the recognition of DDIs. E-prescriptions and dispensing programmes associated with a DDI knowledge base can help health professionals identify hazardous drug combinations.


Intensive Care Unit Intensive Care Unit Admission Intensive Care Unit Stay Charlson Comorbidity Index Intensive Care Unit Discharge 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.



This study was financed by the National Council for Scientific and Technological Development (CNPq) and by the Fundação de Amparo à Pesquisa do Estado da Bahia (FAPESB). The authors have no conflicts of interest that are directly relevant to the content of this study. The authors thank undergraduate students Ludmila Tavares, Jessica Bomfim, Luana Costa and Priscila Guimarães for their participation in collecting data and digitalizing the knowledge base.


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Copyright information

© Adis Data Information BV 2011

Authors and Affiliations

  • Cristiano Moura
    • 1
    Email author
  • Nília Prado
    • 2
  • Francisco Acurcio
    • 3
  1. 1.Multidisciplinary Institute of Health, Federal University of Bahia Vitória da ConquistaBrazil
  2. 2.General Hospital of Vitória da Conquista, Vitória da ConquistaBrazil
  3. 3.Social Pharmacy DepartmentFederal University of Minas GeraisBelo HorizonteBrazil

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