Fatal dose not known.
In the cases of overdosage reported the main effects are drowsiness, lethargy and ataxia. Rarely, A-V block has occurred.
Consider activated charcoal if an adult has ingested more than 150 mg or a child more than 1.5 mg/kg within one hour. Alternatively consider gastric lavage in adults within one hour of a potentially life-threatening overdose. If CNS depression is severe consider the use of flumazenil. It has a short half-life (about an hour). NOT TO BE USED IN MIXED OVERDOSE OR AS A "DIAGNOSTIC" TEST. Management should include general symptomatic and supportive measures including a clear airway and monitoring cardiac and vital signs until stable.