Fatal dose is not known. Adults have survived ingestion of 850 mg without serious sequelae. There is also a potential interaction with tricyclic antidepressants and monoamine-oxidase inhibitors.
These include nausea, vomiting, agitation, tremor, nystagmus, dilated pupils, dry mouth, irritability, sweating and drowsiness leading to coma. Convulsions may occur. Sinus tachycardia is common. Less frequently, bradycardia, hypertension and junctional rhythm may occur.
Rarely features of the "serotonin syndrome" may occur in severe poisoning. This includes alteration of mental status, neuromuscular hyperactivity and autonomic instability. There may be hyperpyrexia and elevation of serum creatine kinase. Rhabdomyolysis is rare.
This should be symptomatic and supportive and include the maintainance of a clear airway and monitoring of cardiac and vital signs until stable. Consider activated charcoal if an adult presents within one hour of ingestion of more than 600 mg or a child more than 5 mg/kg.
Patients should be observed for at least six hours after ingestion of potentially toxic quantities.