Toxicology – Selective Serotonin Reuptake Inhibitor (SSRI) Toxicity

Source

SSRIs are widely used to treat depression, anxiety disorders, and several other psychiatric conditions. Common agents include citalopram, escitalopram, fluoxetine, fluvoxamine, paroxetine, and sertraline.

Typical Presentation

Most isolated SSRI overdoses cause only mild symptoms. Patients may present with nausea, vomiting, drowsiness, agitation, or changes in heart rate. More serious toxicity can occur with large exposures, certain agents, or when serotonin-enhancing drugs are combined.

Clinical Features

Possible effects include:

• Nausea and vomiting
• Tachycardia or bradycardia
• Drowsiness or agitation
• Ataxia
• Altered mental status
• Rarely, coma

Citalopram and escitalopram are particularly associated with QT prolongation and cardiac conduction abnormalities.

Severe serotonergic excess may cause serotonin syndrome, characterized by:

• Agitation or confusion
• Hyperreflexia, clonus, or muscle rigidity
• Tremor or myoclonus
• Tachycardia
• Diaphoresis
• Hyperthermia
• Nausea and vomiting
• Autonomic instability

Mechanism of Action

SSRIs inhibit serotonin reuptake, increasing serotonin concentrations and receptor stimulation within the central nervous system. Excessive serotonergic activity can produce serotonin syndrome.

Management

Treatment is primarily supportive:

• Airway and cardiorespiratory monitoring
• IV fluids when needed
• Benzodiazepines for agitation, tremor, or seizures
• Active cooling for significant hyperthermia
• Continuous ECG monitoring when cardiac toxicity is a concern
• Cyproheptadine may be considered in significant serotonin syndrome under specialist guidance

Severe serotonin syndrome may require intensive supportive care, including airway management and sedation.

Key Points

• Isolated SSRI overdoses are generally less cardiotoxic than tricyclic antidepressant or MAOI poisoning.
• Citalopram and escitalopram deserve particular attention because of their potential for QT prolongation.
• Serotonin syndrome is suggested by the combination of altered mental status, autonomic instability, and neuromuscular hyperactivity.
• Clinical observation and ECG findings help determine the appropriate duration of monitoring.