Selective serotonin reuptake inhibitor toxicity

Background

• Most serious adverse effect is potential to produce serotonin syndrome
  • However, serotonin syndrome unlikely to occur unless co-ingested with other serotonergic drug classes (MAOIs, SNRI, TCAs, amphetamines, opiates)
• Pure overdoses are generally benign (mortality uncommon). Associated with less toxicity than tricyclic antidepressants.
• 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)
• 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 and vomiting
  • Agitation
  • Ataxia
  • Confusion
• Signs
  • Altered mental status
  • Autonomic instability
    • Diaphoresis
    • Hyperthermia
    • Hypertension/hypotension
    • Sinus tachycardia
  • Neuromuscular hyperactivity
    • Hyperreflexia
    • Muscular rigidity
    • Resting tremor

Differential Diagnosis

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

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

Evaluation

Workup

• ECG
  • QRS, QT prolongation (citalopram only)

Management

• Treatment is mostly supportive. Consult poison control for guidance, if needed.
• 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
    • Magnesium sulfate 2g IV if QTc > 500 msec
• Manage seizures with benzodiazepines
• Manage hyperthermia
• If suspecting Serotonin Syndrome, stop all serotonergic medication:
  • SSRIs
  • Anticonvulsants (valproate)
  • Antiemetics (ondansetron, metoclopramide)
  • Analgesics (fentanyl, tramadol, methadone)
  • Antibiotics (linezolid)

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

External Links

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