Recommendations
Key Recommendations
Benzodiazepine overdose is usually determined by the patient's history, either from his or her own report, or by circumstantial evidence, such as benzodiazepine prescriptions or a history of psychiatric illness or previous overdose.
The key factors in making the diagnosis are signs and symptoms of central nervous system (CNS) depression, particularly drowsiness with unremarkable vital signs and no focal signs on neurological examination.
Alcohol and other CNS depressants potentiate the effects of benzodiazepines and increase the toxicity.
Always consider the possibility of a mixed overdose involving paracetamol or other drugs, particularly if you suspect an intentional overdose.
Symptoms and signs of benzodiazepine overdose may be non-specific and highly variable. Ataxia and altered mental state are the most common features. Typical signs of CNS depression include:
Slurred speech
Incoordination
Unsteady gait
Impaired attention or memory, especially the loss of anterograde memory (ask the patient about recent events since exposure, such as who brought them to hospital and how).
Other physical signs may include nystagmus and decreased deep tendon reflexes. More subtle signs of impaired mental status include inappropriate behaviour or judgment, and labile mood. Hypothermia and rhabdomyolysis can also occur in severe cases.[24]
Respiratory depression can occur but is rarely serious if benzodiazepines are taken alone.Coma can occur, usually lasting a few hours.[24]
Coma may be prolonged in older patients.
Ask about:
The specific benzodiazepine taken (if known) and thedose and time of ingestion
Use this information and an estimated or actual weight, to establish whether a toxic dose has been taken (clinical and patient factors may affect what constitutes a toxic dose). See TOXBASE or consult your National Poisons Information Service for toxic doses of benzodiazepines. National Poisons Information Service: TOXBASE Opens in new window
Co-ingestion of alcohol or other substances. Alcohol and other CNS depressants potentiate the effects and increase the toxicity.[24]
Practical tip
The respiratory depressant effects of benzodiazepines may be more severe in patients with COPD.[24]
Proceed sensitively to establish whether the overdose was accidental or intentional. If deliberate self-poisoning has taken place, request a specialist mental health assessment at the earliest opportunity.[18] For further information, see Suicide risk mitigation.
Check and monitor conscious level, blood pressure, oxygen saturations, respiratory rate, and other vital signs.
Hypotension can occur but is rarely serious for an overdose of benzodiazepine alone.[24]
Check and record pupil size.[24]
Initial tests include a rapid bedside determination of blood glucose, full blood count, urea and electrolytes, and liver function tests.
Liver function tests would be expected to be normal following a pure benzodiazepine overdose.
Abnormalities may suggest co-ingestion of another agent (e.g., paracetamol).
Patients with severe liver disease are at risk of toxicity from lower doses.[24] Poor liver function may be a precipitating factor for the benzodiazepine overdose.
Following a significant overdose and reduced conscious level, patients may develop acute kidney injury with or without rhabdomyolysis.
Check creatine kinase where there is concern about a long lie or convulsions with the potential for rhabdomyolysis.[24]
A urine toxicology screen is generally not recommended, as it will not affect the acute management of the patient due to the length of processing time before the result is available.
Consider the possibility of a mixed overdose involving paracetamol or other drugs, particularly if you suspect an intentional overdose:
Measure plasma paracetamol concentration in a patient who is unconscious or is unable to give a reliable history.[28]
See Paracetamol overdose in adults for more information.
Consider arterial or venous blood gas analysis if your patient has:[24]
Reduced oxygen saturation noted on pulse oximetry
Reduced level of consciousness
Metabolic disturbance.
Perform an ECG looking for any abnormality that may be associated with benzodiazepine toxicity, such as first degree and second degree heart block and QT prolongation.[24] Consider repeating in symptomatic patients, those with an abnormal result, or in those in which the recommended observation period is not complete.[24]
CNS depression can mirror respiratory depression; closely observe patients with deteriorating levels of consciousness for any deterioration in oxygen saturation.
Never use a trial of flumazenil as a diagnostic test.[24] Flumazenil use has been associated with convulsions, particularly in patients who have co-ingested drugs associated with seizures.
Do not use immunoassay screening tests.
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