title: Adult clonidine overdose: prolonged bradycardia and central nervous system depression, but not severe toxicity.
abstract: BACKGROUND
  There are limited reports of adult clonidine overdose. We aimed to describe the clinical effects and treatment of clonidine overdose in adults.
  
  
  METHODS
  This was a retrospective review of a prospective cohort of poisoned patients who took clonidine overdoses (>200 μg). Demographic information, clinical effects, treatment, complications (central nervous system and cardiovascular effects) and length of stay (LOS) were extracted from a clinical database or medical records.
  
  
  RESULTS
  From 133 admissions for clonidine poisoning (1988-2015), no medical record was available in 14 and 11 took staggered ingestions. Of 108 acute clonidine overdoses (median age 27 years; 14-65 years; 68 females), 40 were clonidine alone ingestions and 68 were clonidine with co-ingestants. Median dose taken was 2100 μg (interquartile range [IQR]: 400-15,000 μg). Median LOS was 21h (IQR: 14-35 h) and there were no deaths. Glasgow coma score [GCS] <15 occurred in 73/108 (68%), and more patients taking co-ingestants (8/68; 12%) had coma (GCS <9) compared to clonidine alone (2/40; 5%). Miosis occurred in 31/108 (29%) cases. Median minimum HR was 48 bpm (IQR: 40-57 bpm), similar between clonidine alone and co-ingestant overdoses. There was a significant association between dose and minimum HR for clonidine alone overdoses (p = 0.02). 82/108 (76%) had bradycardia, median onset 2.5 h post-ingestion (IQR: 1.7-5.5 h) and median duration 20 h (2.5-83 h), similar for clonidine alone and co-ingestant overdoses. There were no arrhythmias. Three patients ingesting 8000-12,000 μg developed early hypertension. Median minimum systolic BP was 96 mmHg (IQR: 90-105 mmHg) and hypotension occurred in 26/108 (24%). 12/108 patients were intubated, but only 2 were clonidine alone cases. Treatments included activated charcoal (24), atropine (8) and naloxone (23). The median total naloxone dose was 2 mg (IQR: 1.2-2.4 mg), but only one patient given naloxone was documented to respond with partial improvement in GCS.
  
  
  CONCLUSIONS
  Clonidine causes persistent but not life-threatening clinical effects. Most patients develop mild central nervous system depression and bradycardia. Naloxone was not associated with improved outcomes.
authors.affiliation: a Clinical Toxicology Research Group , University of Newcastle , Newcastle , Australia.|b Department of Clinical Toxicology and Pharmacology , Calvary Mater Newcastle , Newcastle , Australia.
authors.forename: Geoffrey K
authors.initials: GK
authors.lastname: Isbister
authors.affiliation: b Department of Clinical Toxicology and Pharmacology , Calvary Mater Newcastle , Newcastle , Australia.
authors.forename: Simon P
authors.initials: SP
authors.lastname: Heppell
authors.affiliation: a Clinical Toxicology Research Group , University of Newcastle , Newcastle , Australia.|b Department of Clinical Toxicology and Pharmacology , Calvary Mater Newcastle , Newcastle , Australia.
authors.forename: Colin B
authors.initials: CB
authors.lastname: Page
authors.affiliation: a Clinical Toxicology Research Group , University of Newcastle , Newcastle , Australia.
authors.forename: Nicole M
authors.initials: NM
authors.lastname: Ryan
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000931:Antidotes / Q000627:therapeutic use; D000959:Antihypertensive Agents / Q000506:poisoning*; D001285:Atropine / Q000627:therapeutic use; D001919:Bradycardia / Q000139:chemically induced* / Q000453:epidemiology; D002493:Central Nervous System Diseases / Q000139:chemically induced* / Q000453:epidemiology; D003000:Clonidine / Q000506:poisoning*; D062787:Drug Overdose; D005260:Female; D015600:Glasgow Coma Scale; D006801:Humans; D007902:Length of Stay; D008297:Male; D008875:Middle Aged; D009270:Naloxone / Q000627:therapeutic use; D012189:Retrospective Studies; D055815:Young Adult
chemical_list: D000931:Antidotes; D000959:Antihypertensive Agents; D009270:Naloxone; D001285:Atropine; D003000:Clonidine
keywords: Clonidine; bradycardia; imidazoline; overdose; poisoning