Benzodiazepine overdosage: plasma concentrations and clinical outcome.

Plasma concentrations and their relation to clinical outcome were evaluated in 21 patients who reached emergency treatment facilities following acute overdosage with benzodiazepine derivatives. Diazepam was implicated in 18 of the 21 cases, with plasma diazepam levels ranging from 585-8,635 ng/ml. In four cases of overdosage with diazepam alone, patients were minimally sedated and were discharged within 24 h, despite diazepam doses as high as 750 mg and plasma levels as high as 4,792 ng/ml. However, concurrent ingestion of diazepam together with other central depressant drugs (such as ethanol, barbiturates, analgesics, or tricyclic antidepressants) produced serious intoxication in 5 of the remaining 14 patients, regardless of the diazepam dosage or plasma concentration. Thus the severity of poisoning following benzodiazepine overdosage is determined largely by co-ingestion of other central depressants rather than the amount of benzodiazepine ingested or its concentration in plasma.