title: The prevalence of QT prolongation in a population of patients with substance use disorders.
abstract: Drug induced QT prolongation occurs in patients with substance use disorders from prescription medications that prolong the QT, such as methadone. Knowing the prevalence of QT prolongation in this population is important for prescribers. This study aimed to investigate the prevalence of QT prolongation in patients with current substance use disorders.
  
  
  
  We undertook a retrospective review of electrocardiograms (ECG) from patients with substance use disorders from an urban general hospital with a large drug and alcohol service and toxicology unit. ECGs were taken from patients seen by the alcohol and drug unit over three years. The QT interval was measured manually on each ECG and defined as abnormal if above the line on the QT nomogram. The QT was also heart rate corrected using Fridericia's formula (QTcF) to investigate associated factors.
  
  
  
  Nine of 446 (2.0%; 95% confidence interval 1.0-3.9%) patients had an ECG with a prolonged QT interval. Three were prescribed methadone for opiate dependence (80, 90 and 125 mg daily), one also with hypokalemia; one prescribed escitalopram with hypokalaemia/hypomagnesaemia; three more with hypokalaemia alone. Only two patients had a prolonged QT with no identifiable cause. There was no association between QTcF and sex (P = 0.34), but there was a statistically significant association with age (Pearson R = 0.19, 95% confidence interval 0.10-0.28, P < 0.0001).
  
  
  
  QT prolongation is rare in patients with substance use disorders and is most likely similar to the general population once cases related to methadone use and electrolyte abnormalities are excluded. [Scott AJ, Dunlop AJ, Brown A, Craig S. The prevalence of QT prolongation in a population of patients with substance use disorders. Drug Alcohol Rev 2017;36:239-244].
authors.affiliation: School of Medicine and Public Health, University of Newcastle, Newcastle, Australia.
authors.forename: Alexander J
authors.initials: AJ
authors.lastname: Scott
authors.affiliation: School of Medicine and Public Health, University of Newcastle, Newcastle, Australia.|Drug and Alcohol Clinical Services, Hunter New England Local Health District, Newcastle, Australia.
authors.forename: Adrian J
authors.initials: AJ
authors.lastname: Dunlop
authors.affiliation: Drug and Alcohol Clinical Services, Hunter New England Local Health District, Newcastle, Australia.
authors.forename: Amanda
authors.initials: A
authors.lastname: Brown
authors.affiliation: School of Medicine and Public Health, University of Newcastle, Newcastle, Australia.|Alcohol and Drug Unit, Calvary Mater Newcastle, Newcastle, Australia.
authors.forename: Craig
authors.initials: C
authors.lastname: Sadler
authors.affiliation: School of Medicine and Public Health, University of Newcastle, Newcastle, Australia.|Department of Clinical Toxicology and Pharmacology, Calvary Mater Newcastle, Newcastle, Australia.
authors.forename: Geoffrey K
authors.initials: GK
authors.lastname: Isbister
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D004562:Electrocardiography; D005260:Female; D006769:Hospitals, General; D006801:Humans; D008133:Long QT Syndrome / Q000139:chemically induced* / Q000453:epidemiology / Q000209:etiology; D008297:Male; D008691:Methadone / Q000008:administration & dosage / Q000009:adverse effects*; D008875:Middle Aged; D009293:Opioid-Related Disorders / Q000534:rehabilitation; D015995:Prevalence; D012189:Retrospective Studies; D012307:Risk Factors; D019966:Substance-Related Disorders / Q000150:complications* / Q000453:epidemiology
chemical_list: D008691:Methadone
keywords: QT interval; drug and alcohol; electrocardiogram; methadone; population