title: Drug-drug interactions contributing to QT prolongation in cardiac intensive care units.
abstract: OBJECTIVE
  To determine the most common drug-drug interaction (DDI) pairs contributing to QTc prolongation in cardiac intensive care units (ICUs).
  
  
  METHODS
  This retrospective evaluation included patients who were admitted to the cardiac ICUs between January 2009 and July 2009 aged ≥ 18 years with electrocardiographic evidence of a QTc ≥ 500 ms. Patients receiving at least two concomitant drugs known to prolong the QT interval were considered to experience a pharmacodynamic DDI. Drugs causing CYP450 inhibition of the metabolism of QT prolonging medications were considered to cause pharmacokinetic DDIs. The causality between drug and QTc prolongation was evaluated with an objective scale.
  
  
  RESULTS
  One hundred eighty-seven patients experienced QT prolongation out of a total of 501 patients (37%) admitted during the study period. Forty-three percent and 47% of patients experienced 133 and 179 temporally-related pharmacodynamic and pharmacokinetic interactions, respectively. The most common medications related to these DDIs were ondansetron, amiodarone, metronidazole, and haloperidol.
  
  
  CONCLUSIONS
  DDIs may be a significant cause of QT prolongation in cardiac ICUs. These data can be used to educate clinicians on safe medication use. Computerized clinical decision support could be applied to aid in the detection of these events.
authors: Cardiothoracic Intensive Care Unit, UPMC, Pittsburgh, PA, USA.
authors: Michael J
authors: MJ
authors: Armahizer
authors: Amy L
authors: AL
authors: Seybert
authors: Pamela L
authors: PL
authors: Smithburger
authors: Sandra L
authors: SL
authors: Kane-Gill
mesh_terms: D000638:Amiodarone / Q000009:adverse effects; D014151:Anti-Anxiety Agents / Q000009:adverse effects; D000889:Anti-Arrhythmia Agents / Q000009:adverse effects; D000890:Anti-Infective Agents / Q000009:adverse effects; D014150:Antipsychotic Agents / Q000009:adverse effects; D054316:Biomarkers, Pharmacological / Q000378:metabolism; D004347:Drug Interactions; D004562:Electrocardiography; D005260:Female; D006220:Haloperidol / Q000009:adverse effects; D006801:Humans; D007362:Intensive Care Units; D008133:Long QT Syndrome / Q000139:chemically induced*; D008297:Male; D008795:Metronidazole / Q000009:adverse effects; D008875:Middle Aged; D017294:Ondansetron / Q000009:adverse effects; D012189:Retrospective Studies; D012307:Risk Factors
chemical_list: D014151:Anti-Anxiety Agents; D000889:Anti-Arrhythmia Agents; D000890:Anti-Infective Agents; D014150:Antipsychotic Agents; D054316:Biomarkers, Pharmacological; D008795:Metronidazole; D017294:Ondansetron; D006220:Haloperidol; D000638:Amiodarone