Serotonin Syndrome - What is It?

• Potentially life-threatening condition associated with increased serotonergic activity in the CNS.
• Selective serotonin reuptake inhibitors (SSRIs) are the most commonly implicated class of medications.  However, other medications can also be involved.
• It is a clinical diagnosis!
• Classic triad: mental status change, autonomic hyperactivity, and neuromuscular abnormalities
  • Mental status change - anxiety, agitation, restlessness, disorientation
  • Autonomic hyperactivity - diaphoresis, tachycardia, hypertension, hyperthermia, nausea, vomiting, diarrhea
  • Neuromuscular abnormalities - tremor, muscle rigidity, myoclonus, hyperreflexia, clonus, Babinski sign (abnormal plantar reflex)
• Hunter Criteria is the most accurate diagnostic rule:
  • Serotonergic agent + one of the following:
    • Spontaneous clonus
    • Inducible clonus + agitation or diaphoresis
    • Ocular clonus + agitation or diaphoresis
    • Tremor + hyperreflexia
    • Hypertonia + temperature above 38C + ocular clonus or inducible clonus
• Majority of cases present within 24 hours, most within 6 hours, of a change in dose or initiation of a medication.

 

** Stay tuned for part 2 on what causes serotonin syndrome **

 

References

• Boyer EW, Shannon M. The serotonin syndrome. N Engl J Med. 2005;352:1112-1120.
• Dunkley EJ, Isbister GK, Sibbritt D, Dawson AH, Whyte IM. The Hunter Serotonin Toxicity Criteria: simple and accurate diagnostic decision rules for serotonin toxicity. QJM. 2003;96(9):635.

 

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