Unifying Concepts

Diagnostic Criteria for Serotonin Syndrome (SS)

Serotonin syndrome is a potentially life-threatening condition resulting from increased CNS serotonergic activity that is usually drug related. Symptoms may include mental status changes, hyperthermia, and autonomic and neuromuscular hyperactivity.

Diagnostic Criteria for Serotonin Syndrome (SS)
Sternbach´s Criteria
Must have recent addition of known serotonergic agent, absence of other causes, and no recent addition of a neuroleptic agent and must exhibit at least 3 of the following:

  • Mental status changes
  • Agitation
  • Hyperreflexia
  • Myoclonus
  • Diaphoresis
  • Shivering
  • Tremor
  • Diarrhea
  • Incoordination
  • Elevated temperature

Radomski´s Criteria
Mild state:

  • Restlessness
  • Insomnia
  • Incoordination
  • Dilated pupils
  • Akathisia
  • Tachycardia
  • Tachypnea/dyspnea
  • Diarrhea
  • Autonomic instability

Severe state:

  • Impaired level of consciousness
  • Elevated mood
  • Coma
  • Myoclonus
  • Tremor
  • Shivering
  • Rigidity
  • Hyperreflexia
  • Hyperthermia
  • Sweating

Hunter´s Criteria
Must have taken a serotonergic agent and meet one of the following criteria:

  • Spontaneous clonus
  • Inducible clonus plus agitation or diaphoresis
  • Ocular clonus plus agitation or diaphoresis
  • Tremor plus hyperreflexia
  • Hypertonia plus temperature higher than 38 °C plus ocular clonus or inducible clonus



  1. Boyer EW, Shannon M. The serotonin syndrome. N Engl J Med. 2005 Mar 17;352(11):1112-20. [Medline]
  2. Cooper BE, Sejnowski CA. Serotonin syndrome: recognition and treatment. AACN Adv Crit Care. 2013 Jan-Mar;24(1):15-20. [Medline]
  3. Iqbal MM, Basil MJ, Kaplan J, Iqbal MT. Overview of serotonin syndrome. Ann Clin Psychiatry. 2012 Nov;24(4):310-8. [Medline]


Created Oct 07, 2014.

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