title: Electrocardiogram changes and arrhythmias in venlafaxine overdose.
abstract: OBJECTIVE
  To investigate serial electrocardiogram (ECG) parameters, haemodynamic changes and arrhythmias following venlafaxine overdose.
  
  
  METHODS
  The study included 369 venlafaxine overdoses in 273 patients presenting to a toxicology unit where an ECG was available. Demographic information, details of ingestion, haemodynamic effects [heart rate and blood pressure (BP)] and complications (arrhythmias and conduction defects) were obtained. ECG parameters (QT, QRS) were measured manually and analysed by visual inspection, including plotting QT-HR pairs on a QT nomogram.
  
  
  RESULTS
  The median ingested dose was 1500 mg [interquartile range (IQR) 600-3000 mg; range 75-13 500 mg). Tachycardia occurred in 54% and mild hypertension (systolic BP >140 mmHg) in 40%. Severe hypertension (systolic BP >180 mmHg) and hypotension (systolic BP <90 mmHg) occurred in 3% and 5%, respectively. No arrhythmias occurred based on continuous telemetry, and conduction defects were found in only seven of 369 admissions; five of these conduction defects were pre-existing abnormalities. In 22 admissions [6%, 95% confidence interval (CI) 4-10] there was an abnormal QT-HR pair, with larger doses being more likely to be associated with an abnormal QT. The median maximum QRS width was 85 ms (IQR 80-90 ms; range 70-145 ms) and the QRS was greater than 120 ms in only 24 admissions (7%, 95% CI 4-10).
  
  
  CONCLUSIONS
  Venlafaxine overdose causes only minor abnormalities in the QT and QRS intervals, unlikely to be associated with major arrhythmias, except possibly with large doses.
authors: Charles Darwin University, Darwin and Department of Clinical Toxicology and Pharmacology, Calvary Mater Newcastle Hospital, Waratah, Australia. geoffrey.isbister@menzies.edu.au
authors: Geoffrey K
authors: GK
authors: Isbister
mesh_terms: D000328:Adult; D001145:Arrhythmias, Cardiac / Q000139:chemically induced* / Q000209:etiology; D003511:Cyclohexanols / Q000506:poisoning*; D062787:Drug Overdose / Q000150:complications; D004562:Electrocardiography / Q000187:drug effects; D005260:Female; D006329:Heart Conduction System / Q000187:drug effects* / Q000503:physiopathology; D006801:Humans; D008133:Long QT Syndrome / Q000139:chemically induced* / Q000503:physiopathology; D008297:Male; D017367:Selective Serotonin Reuptake Inhibitors / Q000506:poisoning*; D000069470:Venlafaxine Hydrochloride
chemical_list: D003511:Cyclohexanols; D017367:Selective Serotonin Reuptake Inhibitors; D000069470:Venlafaxine Hydrochloride