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Benzodiazepine Receptor Antagonist

Flumazenil

Brand names: Anexate

Used in: Poisoning & Overdose

Flumazenil is a competitive benzodiazepine antagonist used to reverse benzodiazepine sedation, mainly after procedural sedation or iatrogenic over-sedation.

Dosing — being independently re-sourced

ClinCalc Pro is rebuilding its dose data from primary open sources — the manufacturer SmPC (eMC), the WHO Model Formulary and other official references — under clinician review. This drug's structured dose is not yet published here. Confirm all doses against the product SmPC and your local formulary before prescribing.

US labelling (FDA)

Reference — US labelling, may differ from UK

DOSAGE AND ADMINISTRATION Flumazenil injection is recommended for intravenous use only. It is compatible with 5% dextrose in water, lactated Ringer’s and normal saline solutions. If flumazenil injection is drawn into a syringe or mixed with any of these solutions, it should be discarded after 24 hours. For optimum sterility, flumazenil injection should remain in the vial until just before use. As with all parenteral drug products, flumazenil injection should be inspected visually for particulate matter and discoloration prior to administration, whenever solution and container permit. To minimize the likelihood of pain at the injection site, flumazenil injection should be administered …

Source: US FDA prescribing information (openFDA / DailyMed), label dated 2025-02-14. Accessed 2026-06-12. US dosing and indications can differ from UK practice — use UK sources for prescribing decisions.

Clinical monograph

How it works

It competitively antagonises benzodiazepines at the GABA-A receptor benzodiazepine binding site, reversing their sedative and respiratory-depressant effects.

Prescribing in practice

  • It can precipitate seizures and is hazardous in benzodiazepine-dependent patients and in mixed overdoses (for example with tricyclic antidepressants or other proconvulsants), so it is not used routinely in undifferentiated overdose.
  • Its half-life is short, so re-sedation can occur after the effect wears off — observe and be ready to re-dose.
  • Avoid where benzodiazepines are being used to control seizures or raised intracranial pressure, and in long-term benzodiazepine use.

Monitoring

Monitor conscious level, respiratory rate, oxygen saturation and for any seizure activity, and observe for long enough to detect re-sedation as the drug is eliminated.

Counselling the patient

  • Warn the team that reversal is short-lived and that re-sedation and recurrent respiratory depression can follow.
  • Highlight the seizure risk and that flumazenil should not be used as a routine 'wake-up' in undifferentiated or mixed overdose.
  • Discuss any poisoning case with Toxbase/NPIS before considering flumazenil.

Evidence & guidelines

Reserved for selected benzodiazepine reversal; not recommended for routine overdose (Toxbase/NPIS).

Reference: MHRA SPC Anexate; TOXBASE NPIS; Hojer et al. J Toxicol Clin Toxicol 1996 (flumazenil in BZD overdose); Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

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