Flumazenil

GABA-A Antagonist·Toxicology & Antidotes

Reversal of conscious sedation (iatrogenic), pure benzodiazepine overdose in non-habituated patients

REVERSALAnexateAmpoules (500 mcg/5 mL) for…S4TGA

Max Dose

2 mg (STAT)

Half-life

40–80 mins

Seizure Risk

CRITICAL

Resedation

HIGH RISK

Rapid Summary

Overview

Competitive benzodiazepine receptor antagonist. Rapidly reverses benzodiazepine-induced sedation and respiratory depression.

Maximum Dose

Max 2 mg per acute reversal event.

Clinical Focus

Do NOT use in mixed overdoses or chronic benzo users. Stripping benzos off the receptor in a dependent patient will trigger uncontrollable, fatal status epilepticus.

Bottom Line

Flumazenil is the specific benzodiazepine antagonist for reversal of BZD sedation and overdose, but can precipitate seizures in chronic benzodiazepine users and has a shorter half-life than most BZDs.

Formulation & Access

Brand Names

Anexate

Parenteral

Ampoules (500 mcg/5 mL) for IV use only.

Prescribing & PBS

Hospital supply. Restricted.

Indications & Use

Primary

TGA

Reversal of conscious sedation (iatrogenic), pure benzodiazepine overdose in non-habituated patients.

Clinical Place

Highly restricted in ED toxicology. Mostly used by anesthetists to wake patients up post-endoscopy.

Quick reference

Class & Role

GABA-A Antagonist — Competitive benzodiazepine receptor antagonist.

Route / Formulation

Ampoules (500 mcg/5 mL) for IV use only. (Anexate)

Usual Dose & Max

IV 200 mcg over 15 seconds. If no response in 60s, give 100 mcg every 60s. Max 1 mg.

Key Indication Doses

Iatrogenic Reversal (e.g. post-procedure): IV 200 mcg over 15 seconds. If no response in 60s, give 100 mcg every 60s. Max 1 mg. Overdose Reversal: IV 200 mcg. If no response, 300 mcg. If no response, 500 mcg. Max 2 mg. (Strictly in ICU/ED with airway support ready).

Best Uses

Avoid / Cautions

Known seizure disorder, chronic benzodiazepine use, mixed overdose with proconvulsant drugs (TCAs, Bupropion, Venlafaxine). Pregnancy Category B3.

Key Risks

Neurological: Intractable seizures, severe acute benzodiazepine withdrawal syndrome (agitation, confusion, tachycardia). Cardiovascular: Arrhythmias (if combined with proarrhythmic drugs in a mixed overdose).

Key Interactions

TCAs. If a patient overdosed on a TCA and a Benzo, the Benzo is protecting their brain from the TCA-induced seizures. Giving Flumazenil removes the shield, causing immediate, often fatal seizures.

Monitoring

Continuous SpO2, RR, and ECG. The patient MUST be monitored for at least 2 hours post-reversal due to the risk of re-sedation. ABG if hypoxic/hypercapnic.

Clinical Pearl

Flumazenil wears off in 45 minutes. Diazepam lasts for 40 hours. The patient will wake up, talk to you, and then stop breathing an hour later when the Flumazenil washes out. You must observe them closely.

Access

Anexate

Brand: Anexate

Flumazenil

GABA-A Antagonist·Toxicology & Antidotes

Reversal of conscious sedation (iatrogenic), pure benzodiazepine overdose in non-habituated patients

REVERSALAnexateAmpoules (500 mcg/5 mL) for…S4TGA

Max Dose

2 mg (STAT)

Half-life

40–80 mins

Seizure Risk

CRITICAL

Resedation

HIGH RISK

Rapid Summary

Overview

Competitive benzodiazepine receptor antagonist. Rapidly reverses benzodiazepine-induced sedation and respiratory depression.

Maximum Dose

Max 2 mg per acute reversal event.

Clinical Focus

Do NOT use in mixed overdoses or chronic benzo users. Stripping benzos off the receptor in a dependent patient will trigger uncontrollable, fatal status epilepticus.

Bottom Line

Formulation & Access

Brand Names

Anexate

Parenteral

Ampoules (500 mcg/5 mL) for IV use only.

Prescribing & PBS

Hospital supply. Restricted.

Indications & Use

Primary

TGA

Reversal of conscious sedation (iatrogenic), pure benzodiazepine overdose in non-habituated patients.

Clinical Place

Highly restricted in ED toxicology. Mostly used by anesthetists to wake patients up post-endoscopy.

Quick reference

Class & Role

GABA-A Antagonist — Competitive benzodiazepine receptor antagonist.

Route / Formulation

Ampoules (500 mcg/5 mL) for IV use only. (Anexate)

Usual Dose & Max

IV 200 mcg over 15 seconds. If no response in 60s, give 100 mcg every 60s. Max 1 mg.

Key Indication Doses

Best Uses

Avoid / Cautions

Known seizure disorder, chronic benzodiazepine use, mixed overdose with proconvulsant drugs (TCAs, Bupropion, Venlafaxine). Pregnancy Category B3.

Key Risks

Key Interactions

TCAs. If a patient overdosed on a TCA and a Benzo, the Benzo is protecting their brain from the TCA-induced seizures. Giving Flumazenil removes the shield, causing immediate, often fatal seizures.

Monitoring

Continuous SpO2, RR, and ECG. The patient MUST be monitored for at least 2 hours post-reversal due to the risk of re-sedation. ABG if hypoxic/hypercapnic.

Clinical Pearl

Access

Anexate

Brand: Anexate