Lecture Notes: Serotonin Syndrome

Overview

• Definition: Serotonin syndrome is a condition resulting from increased CNS serotonergic activity.
• Presentation: Characterized by:
  • Mental status changes
  • Autonomic instability
  • Neuromuscular hyperactivity

Causes

• Increased dosage of a serotonergic drug
• Combination of multiple serotonergic drugs
• Onset can occur within 3-6 hours after dosage increase or multiple drug intake
• Common drugs involved:
  • SSRIs (Selective Serotonin Reuptake Inhibitors)
  • Lithium
  • Meperidine
  • Triptans
  • Monoamine oxidase inhibitors (MAOIs)
  • Cocaine
• High-risk scenario: SSRI + MAOI

Classic Case Example

• Young female on MAOI for depression
• Uses cocaine
• Prescribed Meperidine for pain and Compazine for nausea
• Worsened condition leading to coma and death

Signs and Symptoms

Mental Status Changes

• Confusion
• Agitation
• Lethargy progressing to coma

Autonomic Instability

• Hyperthermia
• Tachycardia
• Mydriasis (dilated pupils)
• Diaphoresis (excessive sweating)
• Nausea, vomiting, diarrhea

Neuromuscular Hyperactivity

• Hyperkinesia
• Hyperreflexia
• Trismus
• Myoclonus
• Cogwheel rigidity (more prominent in lower extremities)
• Bruxism (teeth grinding)
• Trembling and shaking ("wet dog shakes")

Differential Diagnosis

• Differentiate serotonin syndrome from:
  • Anticholinergic overdose
  • Neuroleptic malignant syndrome
  • Malignant hyperthermia
• Key difference: Presence of diaphoresis, nausea, and vomiting in serotonin syndrome vs. dryness in anticholinergic overdose

Treatment

• Discontinue all serotonergic agents
• Supportive care:
  • ABCs: Airway, Breathing, Circulation
  • Cardiac monitoring
  • IV fluids
  • Benzodiazepines for anxiety, agitation, and tachycardia
  • Cooling blankets for hyperthermia
  • Consider intubation with muscle paralysis if necessary
  • Treat severe hypertension with short-acting antihypertensives (e.g., nitroprusside)
• Cryptoheptadine for cases not controlled by supportive measures