Selective serotonin reuptake inhibitor toxicity

Background

• Most serious adverse effect is potential to produce Serotonin Syndrome
• Fatalities are uncommon with pure overdoses

Clinical Features

• Nausea and vomiting
• Sedation
• Tremor
• Sinus tachycardia
• QRS, QT prolongation (citalopram only)
• Serotonin syndrome
• Coma and seizures (rare)

Differential Diagnosis

• Serotonin syndrome

Anticholinergic toxicity Causes

• Medications
  • Atropine
    • Lomotil toxicity
  • Antihistamines
  • Antidepressants
    • Tricyclic antidepressant (TCA) toxicity
    • Selective serotonin reuptake inhibitor toxicity
  • Antipsychotics
  • Muscle relaxants
  • Anti-Parkinsonians
• Plants
  • Jimson weed (Devil's trumpet)
  • Amanita mushroom

Management

• Supportive care
• No role for activated charcoal or gastric lavage
• Magnesium sulfate 2g IV if QTc > 500 msec
• IV benzodiazepines if agitation or seizures

Disposition

• Consider admission for patients who are tachycardic or lethargic 6hr after ingestion
• ECG before clearing a patient with citalopram ingestion

See Also

• Serotonin syndrome
• SNRI Toxicity

Background

• Selective serotonin reuptake inhibitors (SSRI) are the most commonly prescribed antidepressants in the United States
• Examples include fluoxetine (Prozac), paroxetine (Paxil), fluvoxamine (Luvox), sertraline (Zoloft), escitalopram (Lexapro), and citalopram (Celexa)
• Overdose is generally benign. Associated with less toxicity than tricyclic antidepressants
• Serotonin syndrome unlikely to occur unless co-ingested with other serotonergic drug classes (MAOIs, SNRI, TCAs, amphetamines, opiates)
• Citalopram (>600 mg) and escitalopram (>300mg) are unique, as they may cause dose dependent QT prolongation and increase risk of torsades de pointes

Clinical Features

• Symptoms
  • Nausea/vomiting
  • Agitation
  • Ataxia
  • Confusion
• Signs
  • Altered mental status
  • Autonomic instability
    • Diaphoresis
    • Hyperthermia
    • Hypertension/hypotension
  • Neuromuscular hyperactivity
    • Hyperreflexia
    • Muscular rigidity
    • Resting tremor

Differential Diagnosis

• Neuroleptic Malignant Syndrome
• Acetaminophen Toxicity
• Withdrawal Syndromes
• Encephalitis
• Heatstroke
• Hyperthyroidism
• Meningitis
• Rhabdomyolysis
• Tetanus

Management

• Treatment is mostly supportive. Consult poison control for guidance
• Administer activated charcoal if lethal amount ingested within 1-2 hours
• Continuous cardiac monitoring required for citalopram (>600 mg) and escitalopram (>300mg) for at least 8 hours. If citalopram (>1000 mg) and escitalopram (>500 mg) has been ingested then monitor for 12-24 hours
• Manage seizures w/ benzodiazepines
• Manage hyperthermia
• If suspecting Serotonin Syndrome, stop all serotonergic medication:
  • SSRIs
  • Anticonvulsants (valproate)
  • Antiemetics (ondansetron, metoclopramide)
  • Analgesics (fentanyl, tramadol, methadone)
  • Antibiotics (linezolid)

External Links

• Life in the Fast Lane (LITFL) - SSRI Toxicity