SNRI Toxicity
Background
- Inhibits reuptake of serotonin, norepinephrine and small effect on dopamine
- Examples: venlafaxine, duloxetine
- Adverse effects similar to SSRIs, but more dangerous
- Venlafaxine (Effexor)
- Can produce mild to moderate hypertension
- Duloxetine (Cymbalta)
- Nausea, vomiting, dizziness
Clinical Features
- Sympathomimetic: tachycardia, hypertension, diaphoresis, tremor, mydriasis
- Secondary to inhibition of norepinephrine reuptake
- Sedation
- Seizures
- More common than with SSRI toxicity
- Also common with venlafaxine and bupropion
- Rhabdomyolysis
- 25% occur without seizures
- ECG
- Most common abnormality: sinus tachycardia
- May see QRS widening, QT prolongation and ventricular dysrhythmias
- Serotonin syndrome
Evaluation
- Suggestive history with appropriate clinical features
- ECG
- Assess for rhabdomyolysis
Management
- Supportive Care
- Cardiac monitoring
- Sodium bicarbonate if widened QRS
- IV fluids for hypotension (norepinephrine if refractory)
- Benzodiapazines for seizures
- GI Decontamination
- A single dose of activated charcoal, 1 g/kg (typical adult dose is 50 g), may be given to a patient who presents within one to two hours of ingestion.
- AC should not be given to patients at risk for aspiration
- Cardiac monitoring
Disposition
- Admit all symptomatic patients to a monitored bed
- Monitor for 6 hours, longer for extended-release preparations
See Also
References
- Mills K. Atypical Antidepressants, Serotonin Reuptake Inhibitors, and Serotonin Syndrome In: Tintinalli's Emergency Medicine. 7th ed. McGraw Hill. 2011:1198-2002