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

1. SSRIs
2. MAOIs
3. TCAs
4. Drugs of Abuse: Cocaine, Ecstasy, Marijuana
5. Analgesics: Demerol, fentanyl
6. Antiemetics
7. Triptans
8. Bromocriptine
9. OTC: Cough meds, herbal products, St John’s Wort

Clinical Features

1. Altered Mental Status: Agitated delirium
2. Autonomic Instability: Hyperthermia, Tachycardia
3. Neuromuscular Abnormalities: Myoclonus, ocular clonus, rigidity, Hyperreflexia, tremor
   1. More pronounced in the lower extremities

Diagnosis

• Hunter Toxicity Criteria Decision Rules
  • 84% Sn, 97% Sp
  • Serotonergic agent plus 1 of the following:

1. Spontaneous clonus
2. Inducible clonus AND (agitation or diaphoresis)
3. Ocular Clonus AND (agitation or diaphoresis)
4. Tremor AND hyperreflexia
5. Hypertonia AND temp >38 AND (ocular clonus or inducible clonus)

DDX

1. Neuroleptic Malignant Syndrome (NMS)
2. Anticholinergic toxicity
3. Malignant Hyperthermia
4. Sympathomimetic toxicity
5. Meningitis/encephalitis

Treatment

1. Discontinue all serotonergic drugs
2. Benzos
   1. Goal is to eliminate agitation, neuromuscular abnormalities, elevations in HR/BP
3. Cyproheptadine
   1. Give if benzos and supportive care fail to improve agitation and abnormal vitals
   2. Serotonin antagonist
   3. Give 12mg PO/NG; repeat in 2hr if no initial response (max dose 32mg/d)
   4. Give 4mg q6hr x48hr if pt is responsive to initial dose
4. Treat hyperthermia

Source

• Tintinalli
• UpToDate