Antipsychotic toxicity

Background

• Isolated overdose of antipsychotics is rarely fatal
• Toxicity results in blockade of some or all of the following receptors:
  • Dopamine - extrapyramidal symptoms
  • Alpha-1 - orthostatic hypotension, reflex tachycardia
  • Muscarinic - anticholinergic symptoms
  • Histamine - sedation

Clinical Features

1. Extrapyramidal
   1. Acute dystonia
      1. Tongue protrusion, facial grimacing, trismus, oculogyric crisis
   2. Akathisia
2. CNS
   1. Lethargy, ataxia, dyarthria, confusion, coma
   2. Seizure (1%)
3. Anticholinergic Effects
   1. Tachycardia, dry mucous membranes, dry skin, decreased bowel sounds, delirium
4. ECG changes
   1. Sinus tachycardia
   2. QT prolongation

Treatment

1. Supportive
   1. Hypotension
      1. IVF
      2. Norepi
   2. QT prolongation
      1. Treat all pts w/ QTc >500ms w/ magnesium 2-4gm IV over 10min
2. Extrapyramidal
   1. Diphenhydramine 25-50mg IV/IM OR benztropine 1-2mg IV/IM
   2. Oral therapy with either of above meds should be continued for 2 weeks

Disposition

• Consider discharge after 6hr as long as there are all of the following:
  • No mental status changes
  • Normal HR/BP
  • No orthostatic hypotension
  • Normal QT interval

See Also

• Neuroleptic Malignant Syndrome (NMS)
• Beta-Blocker Toxicity
• Calcium Channel Blocker Toxicity

Source

• Tintinalli