The fatal dose is not known. The effects will be potentiated by alcohol taken at the same time. Toxicity is also potentiated by tricyclic antidepressants and MAOIs.
Nausea, vomiting, agitation, tremor, nystagmus and drowsiness may occur. Convulsions have been reported in a small percentage of cases and may not occur until up to ten hours after ingestion. Sinus tachycardia is common. Less frequently bradycardia, hypertension and junctional rhythm may occur.
Rarely features of the "serotonin syndrome" may occur. This includes alteration of mental status, neuromuscular hyperactivity and autonomic instability. There may be hyperpyrexia and elevation of serum creatine kinase. Rhabdomyolysis is rare.
Consider oral activated charcoal if more than 500 mg has been ingested by an adult or if more than 5 mg/kg has been ingested by a child within one hour. Management should be symptomatic and supportive and include the maintainance of a clear airway and monitoring of cardiac and vital signs until stable.