methohexital

Action and Spectrum

Actions and Spectrum: 

• methohexital is a short-acting barbiturate that is used primarily as an anesthetic agent. Its mechanism of action is thought to involve the enhancement of GABA-mediated inhibitory neurotransmission in the central nervous system (CNS).  
• GABA is the primary inhibitory neurotransmitter in the CNS, and barbiturates like methohexital bind to specific sites on the GABA-A receptor, which increases the opening of chloride ion channels, leading to hyperpolarization of the neuron and inhibition of neurotransmission. 
• The spectrum of activity of methohexital is primarily limited to the induction and maintenance of anesthesia, although it may also be used for conscious sedation in specific medical procedures. methohexital has a rapid onset of action and short duration of effect, making it useful for short surgical procedures or diagnostic tests. 

Drug Interaction

Adverse Reaction

Frequency not defined 

Pruritus 

Rhinitis 

Dyspnea 

Restlessness 

Abdominal pain 

Erythema 

Urticaria 

Hypotension 

Anxiety 

Apnea 

Cardiorespiratory arrest 

Pain 

Ulceration 

Respiratory depression 

Dyspnea 

Thrombophlebitis 

Injection site pain 

Coughing 

Muscle twitching & laryngospasm 

Hiccups 

Necrosis 

Swelling 

Black Box Warning

Black box warning: 

methohexital has a black box warning for the risk of respiratory depression, apnea (temporary cessation of breathing), and profound cardiovascular depression, which can lead to cardiovascular collapse and death, mainly when used in high doses or in combination with other drugs that depress the central nervous system. 

Contraindication / Caution

Contraindications/caution: 

Contraindications: 

• methohexital is contraindicated in patients with known hypersensitivity to barbiturates or any of the components of the formulation.  
• It is also contraindicated in patients with a history of porphyria. This rare genetic disorder affects heme synthesis and can lead to acute attacks of abdominal pain, neurological symptoms, and skin lesions. 

Caution: 

• methohexital should be used with caution in patients with a history of drug abuse or addiction, as it has the potential for abuse and dependence. Patients with a history of psychiatric illness or depression may also be at increased risk for these complications. 
• methohexital should be used cautiously in patients with renal or hepatic impairment, as these organs metabolize and eliminate the drug. Dosage adjustments may be necessary for these patients. 
• methohexital may also cause drowsiness, dizziness, or confusion, impairing a patient’s ability to drive or operate machinery. Patients should be advised not to drive or perform hazardous activities until they know how the drug affects them. 

Pregnancy / Lactation

Pregnancy consideration: Insufficient data available 

Lactation: Excretion of the drug in human breast milk is known 

Pregnancy category: 

Category A: well-controlled and Satisfactory studies show no risk to the fetus in the first or later trimester.   

Category B: there was no evidence of risk to the fetus in animal studies, and there were not enough studies on pregnant women. 

Category C: there was evidence of risk of adverse effects in animal reproduction studies, and no adequate evidence in human studies must take care of potential risks in pregnant women.    

Category D: adequate data with sufficient evidence of human fetal risk from various platforms, but despite the potential risk, and used only in emergency cases for potential benefits.    

Category X: Drugs listed in this category outweigh the risks over benefits. Hence these categories of drugs need to be avoided by pregnant women.    

Category N: There is no data available for the drug under this category. 

Pharmacology

Pharmacology: 

• methohexital is a barbiturate with a rapid onset of action and short duration of effect. It is a potent anesthetic agent primarily used for the induction and maintenance of general anesthesia. 
• methohexital enhances the inhibitory effects of the neurotransmitter GABA (gamma-aminobutyric acid) in the central nervous system by binding to specific sites on the GABA-A receptor. This increases the opening of chloride ion channels, leading to neuron hyperpolarization and neurotransmission inhibition. This mechanism of action produces sedative, hypnotic, and anesthetic effects. 

Pharmacodynamics: 

• methohexital is a short-acting barbiturate that produces dose-dependent central nervous system depression, including sedation, hypnosis, anesthesia, and anticonvulsant effects. Its pharmacodynamics are primarily mediated through its interaction with the GABA-A receptor, which enhances the inhibitory effects of the neurotransmitter GABA. 
• Activation of GABA-A receptors by methohexital leads to an influx of chloride ions into the neuron, hyperpolarizing the membrane potential and inhibiting neurotransmission. This results in the sedative and hypnotic effects of methohexital. methohexital can produce complete anaesthesia at higher doses by depressing the central nervous system and reducing responsiveness to painful stimuli. 

Pharmacokinetics: 

Absorption 

methohexital is administered intravenously (IV) for rapid onset of action. When given intramuscularly (IM), it is absorbed more slowly, and its onset of action is delayed. methohexital is not absorbed orally.  

Distribution 

methohexital is highly lipid soluble and can rapidly cross the blood-brain barrier, resulting in rapid onset of action. It has a relatively small volume of distribution, with a rapid distribution phase, and is primarily bound to plasma proteins.  

Metabolism 

methohexital is metabolized in the liver by oxidative and reductive pathways to inactive metabolites, mainly 1,5-dimethylbarbituric acid. It is a potent inducer of hepatic enzymes, so repeated dosing can increase the metabolism of other drugs metabolized by the same pathway.  

Elimination and Excretion 

methohexital is eliminated primarily through the kidneys, with a half-life of about 3-8 hours. A small amount of the drug is also excreted in the feces. methohexital is not recommended for patients with renal impairment, as the drug and its metabolites can accumulate and cause prolonged sedation. 

Adminstartion

Administration: 

• methohexital is usually given by intravenous (IV) injection, as this route provides the most rapid onset of action.  
• The dose and rate of administration depend on the patient’s age, weight, medical history, and the procedure being performed. A typical starting dose for induction of anesthesia in adults is 1-2 mg/kg of body weight given over 10-30 seconds. 
• The dose can be titrated based on the patient’s response and the required anesthesia level 

Patient Information Leaflet

Patient information leaflet 

Generic Name: methohexital 

Why do we use methohexital? 

methohexital is a short-acting barbiturate that is primarily used as an anesthetic agent. Its rapid onset and short duration of action make it particularly useful for short surgical procedures or anesthesia induction before administering other anesthetic agents. Some of the specific uses of methohexital include: 

• Anesthesia induction: methohexital is commonly used to induce anesthesia, particularly for short procedures such as dental or ophthalmic surgery or for diagnostic procedures such as endoscopy. 
• Sedation: methohexital may also be used for sedation in patients undergoing minor surgical procedures or diagnostic tests, such as electroencephalography (EEG). 
• Treatment of status epilepticus: methohexital may be used to treat status epilepticus, a severe and potentially life-threatening seizure disorder. 
• Euthanasia: In some cases, methohexital may be used as part of a euthanasia protocol for animals.