Methohexital

What is Methohexital?

• Methohexital (Brevital Sodium) is a rapid, ultrashort-acting barbiturate anesthetic.

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Methohexital

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What are the uses of this medicine?

Methohexital (Brevital Sodium) is used in adults as follows:

• For intravenous induction of anesthesia prior to the use of other general anesthetic agents.
• For intravenous induction of anesthesia and as an adjunct to subpotent inhalational anesthetic agents (such as nitrous oxide in oxygen) for short surgical procedures; Brevital may be given by infusion or intermittent injection.
• For use along with other parenteral agents, usually narcotic analgesics, to supplement subpotent inhalational anesthetic agents (such as nitrous oxide in oxygen) for longer surgical procedures.
• As intravenous anesthesia for short surgical, diagnostic, or therapeutic procedures associated with minimal painful stimuli.
• As an agent for inducing a hypnotic state.

Methohexital (Brevital Sodium) is used in pediatric patients older than 1 month as follows:

• For rectal or intramuscular induction of anesthesia prior to the use of other general anesthetic agents.
• For rectal or intramuscular induction of anesthesia and as an adjunct to subpotent inhalational anesthetic agents for short surgical procedures.
• As rectal or intramuscular anesthesia for short surgical, diagnostic, or therapeutic procedures associated with minimal painful stimuli.

How does this medicine work?

• Methohexital produces its effect by potentiating the inhibitory actions of GABA on the GABA (A) receptor.
• At higher concentrations, methohexital directly stimulates and activates the receptor.
• Barbiturates bind to the GABA A receptor and increase the open duration of the GABA A receptor without having any effect on channel opening frequency or conductance.
• Specifically, the downstream effect is on the chloride channel, causing it to stay open longer, causing influx.
• This action causes inhibitory pathways to activate in the brain and causes decreased neuronal excitability, thus inducing anesthesia/sedation.
• Research has shown the highest concentration of methohexital in the hypothalamus, globus pallidus, and the substantia nigra.
• Once the GABA receptor is activated, increased chloride influx causes increases the negative charge on the inside of the membrane resulting in hyperpolarization and thus post-synaptic neuron inhibition.
• Methohexital is a derivative from barbituric acid, which is a compound made of malonic acid and urea.
• The chemical formula for methohexital is 1-methyl-2-pentynyl barbituric acid.
• The acyclic side chain at the fifth Carbon of the benzene ring is responsible for the hypnotic activity attributed to this compound.

Who Should Not Use this medicine ?

This medicine cannot be used in patients:

• in whom general anesthesia is contraindicated
• with latent or manifest porphyria
• with a known hypersensitivity to barbiturates

What drug interactions can this medicine cause?

• Tell your doctor and pharmacist what other prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking or plan to take.

Be sure to mention any of the following:

• phenytoin
• halothane
• anticoagulants
• corticosteroids
• ethyl alcohol
• propylene glycol-containing solutions

Is this medicine FDA approved?

• Yes, it is FDA approved.

How should this medicine be used?

Recommended dosage: Adults:

• Standard adult dosing for anesthesia induction is 50 to 120 mg IV as a bolus.
• General anesthesia maintenance calls for 20 to 40 mg IV every 4 to 7 minutes as needed.
• In pediatrics, general anesthesia induction dosing is 6.6 to 10 mg/kg IM injection once.
• Alternately, 25 mg/kg as a single dose rectally is an option.

Pediatric Patients:

• In pediatrics, methohexital has found application in procedural sedation for obtaining imaging at doses between 0.5 mg/kg to 2.0 mg /kg.
• The use of rectal methohexital is predominantly in the pediatric population; one study reports a dose of 30 mg/kg of 10% methohexital caused 85% of children to fall asleep.
• The induction dose for methohexital for electroconvulsive therapy is 1.5 mg/kg.

Administration:

• Methohexital has a variety of administration routes, including rectal, IV, and IM use.

What are the dosage forms and brand names of this medicine?

This medicine is available in fallowing doasage form:

• As methohexital sodium, USP for injection

This medicine is available in fallowing brand namesː

• Brevital Sodium

What side effects can this medication cause?

The most common side effects of this medicine include: Cardiovascular:

• Circulatory depression, thrombophlebitis, hypotension, tachycardia, peripheral vascular collapse, and convulsions in association with cardiorespiratory arrest

Respiratory:

• Respiratory depression (including apnea), cardiorespiratory arrest, laryngospasm, bronchospasm, hiccups, and dyspnea

Neurologic:

• Skeletal muscle hyperactivity (twitching), injury to nerves adjacent to injection site, and seizures

Psychiatric:

• Emergence delirium, restlessness, and anxiety may occur, especially in the presence of postoperative pain

Gastrointestinal:

• Nausea, emesis, abdominal pain, and liver function tests abnormal

Allergic:

• Erythema, pruritus, urticaria, and cases of anaphylaxis have been reported rarely

Other:

• Other adverse reactions include pain at injection site, salivation, headache, and rhinitis

What special precautions should I follow?

• As with all potent anesthetic agents and adjuncts, Brevital should be used only in hospital or ambulatory care settings that provide for continuous monitoring of respiratory (e.g. pulse oximetry) and cardiac function.
• Maintenance of a patent airway and adequacy of ventilation must be ensured during induction and maintenance of anesthesia with methohexital sodium solution.
• All routes of administration of Brevital are often associated with hiccups, coughing, and/or muscle twitching, which may also impair pulmonary ventilation. Following induction, temporary hypotension and tachycardia may occur.
• Recovery from methohexital anesthesia is rapid and smooth. The incidence of postoperative nausea and vomiting is low if the drug is administered to fasting patients. Postanesthetic shivering has occurred in a few instances.
• The drug should be used with caution in patients with asthma, obstructive pulmonary disease, severe hypertension or hypotension, myocardial disease, congestive heart failure, severe anemia, or extreme obesity.
• Methohexital sodium should be used with extreme caution in patients in status asthmaticus.
• When appropriate, patients should be instructed as to the hazards of drowsiness that may follow use of Brevital. Outpatients should be released in the company of another individual, and no skilled activities, such as operating machinery or driving a motor vehicle, should be engaged in for 8 to 12 hours.
• Studies conducted in young animals and children suggest repeated or prolonged use of general anesthetic or sedation drugs in children younger than 3 years may have negative effects on their developing brains.
• Caution should be exercised when Brevital is administered to a nursing woman.

What to do in case of emergency/overdose?

Symptoms of overdosage may include:

• central nervous system depression, respiratory depression, hypotension, loss of peripheral vascular resistance, and muscular hyperactivity ranging from twitching to convulsive-like movements.
• Other findings may include convulsions and allergic reactions.
• Following massive exposure to any barbiturate, pulmonary edema, circulatory collapse with loss of peripheral vascular tone, and cardiac arrest may occur.

Management of overdosage:

• In case of overdose, call the poison control helpline of your country. In the United States, call 1-800-222-1222.

• Overdose related information is also available online at poisonhelp.org/help.
• In the event that the victim has collapsed, had a seizure, has trouble breathing, or can't be awakened, immediately call emergency services. In the United States, call 911.
• Establish an airway and ensure oxygenation and ventilation.
• Resuscitative measures should be initiated promptly.
• For hypotension, intravenous fluids should be administered and the patient’s legs raised.
• If desirable increase in blood pressure is not obtained, vasopressor and/or inotropic drugs may be used as dictated by the clinical situation.
• For convulsions, diazepam intravenously and phenytoin may be required.
• If the seizures are refractory to diazepam and phenytoin, general anesthesia and paralysis with a neuromuscular blocking agent may be necessary.
• Protect the patient’s airway and support ventilation and perfusion.
• Meticulously monitor and maintain, within acceptable limits, the patient’s vital signs, blood gases, serum electrolytes, etc.
• Absorption of drugs from the gastrointestinal tract may be decreased by giving activated charcoal, which, in many cases, is more effective than emesis or lavage; consider charcoal instead of or in addition to gastric emptying.

Can this medicine be used in pregnancy?

• There are no adequate and well-controlled studies in pregnant women.
• Brevital has been used in cesarean section delivery but, because of its solubility and lack of protein binding, it readily and rapidly traverses the placenta.

Can this medicine be used in children?

• The safety and effectiveness of methohexital sodium in pediatric patients below the age of 1 month have not been established.

What are the active and inactive ingredients in this medicine?

Active ingredient:

• METHOHEXITAL SODIUM

Inactive ingredients:

• SODIUM HYDROXIDE
• SODIUM CARBONATE

Who manufactures and distributes this medicine?

Distributed by:

• Par Pharmaceutical
• Chestnut Ridge, NY

What should I know about storage and disposal of this medication?

• Store between 20° to 25°C (68° to 77°F).

• Dailymed label info on Methohexital
• FDA Methohexital

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