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Flumazenil Side Effects

In Summary

Commonly reported side effects of flumazenil include: dizziness, nausea, and vomiting. Other side effects include: headache, agitation, depersonalization, depression, dysphoria, dyspnea, euphoria, hyperventilation, insomnia, nervousness, palpitations, paranoia, paresthesia, tremor, uncontrolled crying, visual disturbance, diaphoresis, pain at injection site, and xerostomia. See below for a comprehensive list of adverse effects.

For the Consumer

Applies to flumazenil: parenteral injection

Side effects include:

Dizziness, injection site pain, increased sweating, headache, and abnormal or blurred vision.

For Healthcare Professionals

Applies to flumazenil: intravenous solution


Flumazenil is generally well-tolerated when given to patients without prior exposure to benzodiazepines. Convulsions are the most common serious adverse events reported. Dizziness, injection site pain, increased sweating, headache, and visual disturbances have been reported in 3% to 9% of patients. Most of the adverse effects observed during flumazenil therapy are related to the rapid resolution of benzodiazepine effects rather than to the administration of flumazenil per se.[Ref]

Nervous system

Flumazenil has been associated with seizures in patients with severe hepatic insufficiency and patients who were taking benzodiazepines for seizure control. Other risk factors for seizures may include concurrent sedative-hypnotic withdrawal, recent repeated administration of parenteral benzodiazepines, jerking or seizures prior to administration of flumazenil, and concurrent cyclic antidepressant overdose.

Seizures are generally reversible with standard antiepileptic therapy include benzodiazepines, phenytoin or barbiturates. Greater than usual benzodiazepine doses may be required to control seizures which occur in association with flumazenil therapy.

Some investigators have suggested that flumazenil may increase intracranial pressure and should therefore be avoided in patients with space-occupying intracranial lesions.[Ref]

Nervous system side effects have included seizures, agitation, anxiety, nervousness, dry mouth, tremor, palpitations, insomnia, dyspnea, hyperventilation, dizziness, vertigo, ataxia, confusion, somnolence, resedation (as flumazenil's effects wane), headache, and paresthesia have also been reported.[Ref]


Fear and panic attacks have been reported in patients with a history of panic disorders.[Ref]

Psychiatric side effects have included emotional lability (crying, depersonalization, euphoria, depression, dysphoria, and paranoia), psychosis, anxiety, fear, and panic attacks.[Ref]


Local reaction at the site of intravenous injection include pain, burning, swelling, and rash.[Ref]


Gastrointestinal side effects have included nausea and vomiting in 11% of treated patients. Hiccups have been reported in less than 1%.[Ref]


Cardiovascular side effects have included cutaneous vasodilation (sweating, flushing, and hot flashes) in 1% to 3% of patients. Arrhythmias (atrial, nodal, ventricular extrasystoles), tachycardia, bradycardia, premature ventricular depolarizations, heart block, cardiac arrest, hypertension, and chest pain have been reported in less than 1% of patients.[Ref]

Ventricular tachycardia (1/446) and junctional tachycardia (1/446) have been reported in clinical trials of patients with benzodiazepine overdose.

Some investigators have suggested that reports of adverse cardiac effects are related to reversal of benzodiazepine-mediated sedation with consequent increased sympathetic drive, rather than to any intrinsic cardiac effects of flumazenil.

Other investigators and case reports have suggested that cardiovascular effects are most likely to occur in the setting of multiple drug overdose treated with flumazenil rather than isolated benzodiazepine overdose.[Ref]


Fatalities have been reported, the majority of deaths were in patients with overdoses due to nonbenzodiazepine drugs (usually cyclic antidepressants) and in patients with serious underlying disease.[Ref]

Benzodiazepine withdrawal symptoms have been reported following flumazenil treatment in patients receiving chronic (and rarely, acute) benzodiazepine therapy. Such symptoms have included dizziness, tenseness, agitation, anxiety, panic attacks, confusion, tachycardia, perceptual disturbances, and sweating. Withdrawal symptoms may occur in chronic benzodiazepine users after rapid flumazenil injection.[Ref]

Although benzodiazepine withdrawal symptoms have been reported, symptoms are generally mild and transient. One study has reported that no evidence of precipitated withdrawal was observed on psychomotor/behavioral performance studies or observer ratings in subjects pretreated with benzodiazepines.

Another case report has suggested that flumazenil may aggravate seizures in patients undergoing benzodiazepine withdrawal.[Ref]

Other side effects affecting the body as a whole have included fatigue, rigors, and shivering.[Ref]

Tinnitus, hyperacusis, transient hearing impairment, dysphonia, and thick tongue have been reported.[Ref]


Ocular side effects have included abnormal vision, diplopia, and visual field defects.[Ref]


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Some side effects of flumazenil may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA.

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