acute hydroxychloroquine or chloroquine overdose / toxicity (Plaquenil)


  • hydroxychloroquine and chloroquine have relatively narrow therapeutic windows and acute toxicity is a risk, particularly for those who self-prescribe
  • cardiovascular and neurologic toxicity may present within 1-3 hours of ingestion of doses > 10mg/kg of chloroquine (hydroxychloroquine is 2-3x less toxic in animal models)
  • ingestion of > 5g chloroquine may be fatal in adults without intervention, while the average dose causing fatalities is around 8g of chloroquine

Clinical features of acute toxicity

  • hypotension
  • hypokalaemia from intracellular shift
  • widened QRS
  • ST depression
  • U waves (hypokalaemia)
  • AV block
  • ventricular arrhythmias
  • visual disturbances including reversible blindness
  • diplopia
  • photophobia
  • +/- myopathies, neuropathies
  • CNS depression
  • seizures and coma in pre-arrest status
  • death usually occurs within 12hrs, but may be delayed up to 48hrs


  • discuss with a clinical toxicologist
  • decontaminate if within 2hrs ingestion:
    • consider intubation and then activated charcoal via NG if obtunded or if > 5g ingested
  • avoid over-treating hypokalaemia as risk of rebound hyperkalaemia
  • IV fluid 20mL/kg for hypotension +/- IV adrenaline
    • consider high dose diazepam infusion following adrenaline eg. 2mg/kg IV over 30minutes then 1-2mg/kg over 24hrs
  • Rx ventricular arrhythmias:
    • consider IV sodium bicarbonate although this may exacerbate hypokalaemia
  • Rx seizures with benzodiazepines
  • no role for dialysis as large Vd
  • consider ECMO if refractory shock
  • if significant toxicity, admit to a critical care area for 48hrs
  • if clinically well, asymptomatic for 6hrs post ingestion with a normal ECG then clinically clear for MH assessment and Mx
od_hydroxychloroquine.txt · Last modified: 2020/03/26 12:21 (external edit)