What is Brevital (Methohexital)?
Brevital is the brand name for methohexital sodium, a drug classified as an ultra-short-acting barbiturate [1.2.5, 1.3.1]. It is used primarily in hospital or clinical settings under strict supervision to induce a state of unconsciousness or deep sedation before and during medical procedures [1.2.2, 1.2.5]. Due to its rapid onset and short duration of action, it is highly valued for procedures where a quick return to consciousness is desired [1.4.2]. It is a Schedule IV controlled substance, indicating it has the potential for habit formation [1.2.4].
Mechanism of Action: How Brevital Works
Brevital's primary effect is on the central nervous system (CNS). It belongs to the barbiturate class of drugs, which exert their effects by interacting with the gamma-aminobutyric acid (GABA-A) receptor complex in the brain [1.3.1, 1.3.6]. GABA is the main inhibitory neurotransmitter in the CNS. Methohexital binds to a specific site on the GABA-A receptor, which enhances the effect of GABA. This action increases the duration for which the associated chloride ion channel remains open, leading to an influx of chloride ions into the neuron [1.3.6]. This hyperpolarizes the neuron, making it less likely to fire and thus suppressing neuronal activity, resulting in sedation, hypnosis, and amnesia [1.3.5]. At higher concentrations, methohexital can directly stimulate the receptor even in the absence of GABA [1.4.5].
Pharmacokinetics: Absorption, Distribution, Metabolism, and Excretion
- Absorption and Onset: When administered intravenously (IV), Brevital has complete bioavailability and a very rapid onset of action, typically within 20 to 40 seconds [1.4.2, 1.4.3]. Sleep time after a single dose is usually between 5 to 7 minutes [1.2.3].
- Distribution: As a highly lipid-soluble drug, methohexital quickly crosses the blood-brain barrier to produce its anesthetic effects [1.4.4]. Its short duration of action is primarily due to the rapid redistribution of the drug from the brain and other high-blood-flow organs to leaner tissues and eventually to fat stores, where it can be slowly rereleased [1.2.3, 1.4.3].
- Metabolism: The liver is the primary site of metabolism for methohexital, where it undergoes demethylation and oxidation [1.3.6]. This biotransformation is crucial for terminating the drug's biological activity [1.2.3]. Its clearance rate is significantly faster than that of thiopental, another barbiturate [1.2.3].
- Excretion: The inactive metabolites are primarily excreted by the kidneys through urine [1.3.6, 1.4.4]. Less than 1% of the drug is excreted unchanged [1.4.4]. The mean elimination half-life is approximately 3.9 hours [1.2.3].
Clinical Uses and Indications
Brevital is utilized in a variety of clinical scenarios:
- Induction of Anesthesia: It is frequently used to induce general anesthesia before the administration of other anesthetic agents for surgical procedures [1.2.4].
- Procedural Sedation: Its rapid onset and short recovery time make it suitable for short diagnostic or therapeutic procedures that require sedation but are associated with minimal painful stimuli, such as endoscopies or cardioversions [1.3.5, 1.2.1].
- Electroconvulsive Therapy (ECT): Methohexital is considered a preferred agent, and sometimes the "gold standard," for ECT [1.4.5, 1.8.3]. Unlike many other anesthetics, it can lower the seizure threshold, which is beneficial for the efficacy of ECT, as the duration of the seizure is linked to improved outcomes [1.2.5, 1.4.5].
- Pediatric Use: It can be used in children older than one month for induction of anesthesia, typically via intramuscular or rectal routes [1.2.4, 1.5.2].
Brevital vs. Propofol: A Comparison
A common alternative to Brevital is Propofol, another short-acting intravenous anesthetic. The choice between them often depends on the specific procedure and patient factors.
| Feature | Brevital (Methohexital) | Propofol |
|---|---|---|
| Drug Class | Barbiturate | Phenol derivative |
| Mechanism | Enhances GABA-A receptor activity [1.3.4] | Enhances GABA-A receptor activity [1.8.5] |
| Onset | Ultra-rapid (20-40 seconds) [1.4.2] | Rapid (approx. 30 seconds) [1.8.5] |
| Recovery | Generally faster recovery times than propofol in some studies [1.7.2, 1.7.3] | Rapid recovery, but may be slightly longer than Brevital [1.7.2, 1.7.3] |
| ECT Use | Preferred; lowers seizure threshold, prolonging seizure duration [1.2.5, 1.8.5] | Can shorten seizure duration by increasing the seizure threshold [1.8.3] |
| Side Effects | Hiccups, muscle twitching, respiratory depression, less hypotension than propofol [1.2.3, 1.7.3] | Pain on injection, significant hypotension, respiratory depression [1.6.4, 1.7.3] |
Studies comparing the two for procedures like cardioversion have found methohexital to be associated with faster recovery and more stable hemodynamics (less hypotension) [1.7.3]. For ECT, methohexital's ability to facilitate longer seizures often makes it the preferred agent [1.8.5].
Side Effects and Contraindications
Like all anesthetics, Brevital must be administered by trained professionals in a setting with appropriate monitoring and resuscitation equipment [1.2.4].
Common Side Effects: [1.2.2, 1.6.5]
- Respiratory depression or apnea (temporary cessation of breathing) [1.6.3]
- Hiccups, coughing, and muscle twitching [1.6.2]
- Hypotension (low blood pressure) and tachycardia (fast heart rate) [1.6.2]
- Nausea and vomiting [1.2.3]
- Emergence reactions like anxiety or restlessness [1.6.5]
- Pain at the injection site [1.2.3]
Contraindications: Brevital is contraindicated in patients with [1.6.4]:
- Known hypersensitivity to barbiturates.
- A history of porphyria (a group of liver disorders).
- It should be used with extreme caution in patients with status asthmaticus [1.6.2].
Conclusion
Brevital (methohexital) is a potent, ultra-short-acting barbiturate anesthetic with a long history of use in medicine. Its rapid onset, short duration, and unique property of lowering the seizure threshold make it a valuable tool for anesthesia induction, procedural sedation, and particularly as a primary agent for electroconvulsive therapy [1.2.1, 1.2.5]. While newer agents like propofol are also widely used, Brevital maintains a crucial role due to its favorable profile in specific clinical contexts, such as faster recovery and better hemodynamic stability in some procedures [1.7.3]. Proper administration and patient monitoring by a qualified interprofessional team are essential to ensure its safe and effective use [1.2.1].
For more detailed information, consult the official documentation on the FDA website.
