Benzodiazepine Overdose

Benzodiazepines potentiate GABA-A receptor mediated chloride influx, causing central nervous system depression. Overdose with a benzodiazepine alone, in an otherwise healthy adult with no other co-ingestion or comorbidity, is generally associated with a relatively favorable prognosis given the wide therapeutic index of this drug class.

The risk profile changes substantially with co-ingestion of other sedating substances, particularly opioids or alcohol, or in elderly or comorbid patients, where even isolated benzodiazepine overdose can cause significant respiratory compromise.

• Drowsiness, slurred speech, ataxia, and confusion, progressing to stupor or coma in more significant overdose
• Respiratory depression, generally milder than with opioid overdose when benzodiazepines are taken alone, but potentially severe with large ingestions or in combination with other CNS depressants
• Hypotension, though this is generally mild in isolated benzodiazepine toxicity
• Paradoxical agitation, particularly in the elderly or in children, is a recognized, less common presentation

Diagnosis is primarily clinical, based on history and the presenting sedative toxidrome.

• Blood glucose should be checked to exclude hypoglycemia as a contributor to reduced consciousness.
• A thorough history of co-ingestion is essential, given how frequently benzodiazepines are taken alongside alcohol or other sedatives in overdose, and how much this changes both risk and management.
• Paracetamol and salicylate levels should be checked given the frequency of co-ingestion in intentional overdose.
• Urine toxicology screening may support diagnosis but has limited immediate clinical utility given cross reactivity and variable sensitivity across different benzodiazepines.

Differentials include other sedative toxidromes (opioid, alcohol), hypoglycemia, and primary CNS pathology, particularly where the clinical picture does not fit cleanly or fails to improve as expected with supportive care.

Supportive care is the mainstay of treatment for the large majority of cases: airway protection as needed, careful monitoring of respiratory status and consciousness level, and general supportive measures until the drug is metabolized and cleared.

• Flumazenil, a competitive benzodiazepine receptor antagonist, is available as an antidote but is used with considerable caution and is not given routinely, given a significant risk of precipitating seizures, particularly in patients who are benzodiazepine dependent, have co-ingested a pro-convulsant substance (such as a tricyclic antidepressant), or have a seizure disorder.
• Flumazenil is generally reserved for specific situations, such as reversing iatrogenic over-sedation following a procedure in a patient with no benzodiazepine dependence or seizure risk, rather than for undifferentiated self poisoning, where the risk benefit balance is usually unfavorable.
• Where flumazenil is used, it is given as 0.2 mg intravenously over 15 to 30 seconds, repeated in increments of 0.1 to 0.2 mg at 1 minute intervals, titrated carefully to effect, to a typical cumulative dose of 1 to 3 mg. Its duration of action is shorter than most benzodiazepines, so re-sedation can occur and the patient requires observation, or a repeat dose, after apparent reversal.
• Assessment for co-ingestion and its specific management is essential, given how often isolated benzodiazepine overdose is not truly isolated.

Referral: psychiatry for assessment following any intentional overdose; ICU for significant respiratory compromise or where airway protection is required.