Overview
Methohexital is an ultra-short-acting barbiturate anesthetic agent used primarily for induction of anesthesia and for short surgical procedures. It produces rapid onset of hypnosis (within 30-60 seconds) with a short duration of action (5-7 minutes). It is administered intravenously and has no analgesic properties.
Mechanism of Action
Methohexital acts primarily as a GABA-A receptor agonist, enhancing inhibitory neurotransmission in the central nervous system. It increases the duration of chloride channel opening at GABA receptors, leading to neuronal hyperpolarization and CNS depression.
Indications
- Induction of general anesthesia
- Maintenance of anesthesia for short surgical procedures
- As an adjunct in balanced anesthesia techniques
Dosage
IV administration only. Induction: 50-120 mg (1-1.5 mg/kg) given over 30-60 seconds. Maintenance: 20-40 mg every 4-7 minutes as needed. Maximum single dose: 600 mg. Maximum 24-hour dose: 2 g.
Contraindications
- Absolute hypersensitivity to barbiturates
- Acute intermittent porphyria
- Status asthmaticus
- Severe cardiovascular instability
Side Effects
- Respiratory depression
- Hypotension
- Injection site pain
- Hiccups
- Sneezing
- Coughing
- Muscle twitching
- Nausea/vomiting
- Headache
- Emergence delirium
Interactions
- Enhanced CNS depression with other CNS depressants (alcohol, opioids, benzodiazepines)
- Reduced effectiveness of oral anticoagulants
- Decreased metabolism of other drugs metabolized by CYP450 enzymes
- Increased risk of hypotension with antihypertensive agents