Venlafaxine and desvenlafaxine are potent selective serotonin and noradrenaline reuptake-inhibitor. Venlafaxine overdose is potentially life threatening; it frequently causes seizures and in very large ingestions, cardiovascular toxicity. Supportive care and adequate benzodiazepine sedation usually ensure a good outcome. There is less clinical experience with desvenlafaxine but it is likley that the clinical features in overdose will be similar to those of venlafaxine.
| Dose | Effect |
| <1.5 g | Risk of seizures <5% |
| < 3 g | Risk of seizures 10% |
| > 3 g | Risk of seizures >30% |
| >4.5 g | Risk of seizures approaches 100% Hypotension Minor QRS and QT prolongation on 12-lead ECG |
| >7 g | Hypotension and cardiac dysrhythmias |
References
- Howell C, Wilson AD, Waring WS. Cardiovascular toxicity due to venlafaxine poisoning in adults: a review of 235 consecutive cases. British Journal of Clinical Pharmacology 2007; 64(2):192-197.
- Isbister GK. Electrocardiogram changes and arrhythmias in venlafaxine overdose. British Journal of Clinical Pharmacology 2009; 67(5):572-576.
- Whyte IM, Dawson AH, Buckley NA. Relative toxicity of venlafaxine and selective serotonin reuptake inhibitors in overdose compared to tricyclic antidepressants. Quarterly Journal of Medicine 2003; 96(5): 369-374.
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