Serotonin syndrome

Background

• Can be produced by any serotonergic medication
• Vast majority of cases occur with therapeutic dosages
• Most common cause of death is severe hyperthermia

Causative Agents

• SSRIs
• MAOIs
• TCAs
• Drugs of Abuse: Cocaine, Ecstasy, Marijuana
• Analgesics: Demerol, fentanyl
• Antiemetics
• Triptans
• Bromocriptine
• OTC: Cough meds, herbal products, St John’s Wort

Clinical Features

• Altered mental status: Agitated delirium
• Autonomic Instability: Hyperthermia, Tachycardia, diaphoresis
• Neuromuscular Abnormalities: Myoclonus, ocular clonus, rigidity, hyperreflexia, tremor
  • More pronounced in the lower extremities
  • Myoclonus: most common finding
    • Important to identify because it does not occur in other conditions that mimic serotonin syndrome

Differential Diagnosis

• Neuroleptic Malignant Syndrome (NMS)
• Anticholinergic Toxicity
• Malignant Hyperthermia
• Sympathomimetic toxicity
• Meningitis
• Encephalitis
• Delirium tremens
• Heat stroke

Diagnosis

Hunter Toxicity Criteria Decision Rules

Serotonergic agent plus 1 of the following:

• Spontaneous clonus
• Inducible clonus AND (agitation or diaphoresis)
• Ocular Clonus AND (agitation or diaphoresis)
• Tremor AND hyperreflexia
• Hypertonia AND temp >38 AND (ocular clonus or inducible clonus)

84% Sn, 97% Sp

Treatment

1. Discontinue all serotonergic drugs
2. Benzos
   • Goal is to eliminate agitation, neuromuscular abnormalities, elevations in HR/BP
3. Cyproheptadine
   • Give if benzos and supportive care fail to improve agitation and abnormal vitals
   • Serotonin antagonist
   • Give 12mg PO/NG; repeat with 2mg q2hr until clinical response is seen (max 32mg/d)
   • Give 4mg q6hr x48hr if pt is responsive to initial dose
4. Treat hyperthermia
   • Hyperthermia due to increase in muscular activity, not change in set point
   • Intubate and paralyze
   • Standard cooling measures

See Also

• Toxidromes