Reducing risk of overdose with midazolam injection in adults

This Rapid Response Report alerts all healthcare organisations using midazolam injection for adult conscious sedation to the risk of overdose.

The presentation of high-strength midazolam as 5mg/ml (2ml and 10ml ampoules) or 2mg/ml (5ml ampoule) exceeds the dose required for most patients. There is a risk of administering  the entire contents of high-strength ampoules, when only a fraction of this dose is required.

The National Reporting and Learning Service received 498 patient safety incidents between November 2004 and November 2008 where the dose prescribed or administered to the patient was inappropriate. Three incidents resulted in death.

The reversing agent, flumazenil, is frequently used to treat inadvertent benzodiazepine overdose. Occasionally, no account is taken for the shorter half life of flumazenil (compared to midazolam), leading to residual re-sedation.

Healthcare organisations should:

• Restrict the storage and use of high strength midazolam to clinical areas/situations where its use has been risk-assessed.
• Replace the storage and use of high-strength midazolam with low-strength midazolam in other clinical areas.
• Clarify guidance on the use of midazolam. Ensure that the risks are fully assessed.
• Ensure that staff involved in sedation techniques have the necessary skills. 
• Ensure that flumazenil is available where midazolam is used. Audit the use of flumazenil as a marker of excessive dosing of midazolam.
• Ensure that sedation is covered by organisational policy. Assign overall responsibility to a senior clinician.