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an ultrashort-acting barbiturate; its sodium salt is used as a general anesthetic, a general and local anesthesia adjunct, and a sedative for certain diagnostic procedures in children.
Pregnancy Category: C
ClassificationTherapeutic: general anesthetics
Induction of general anesthesia.Sole anesthesia in short (<15 min), minimally painful procedures.Supplement to other anesthetic agents.To produce unconsciousness during balanced anesthesia.
Produces anesthesia by depressing the CNS, probably by potentiating GABA, an inhibitory neurotransmitter.
Unconsciousness and general anesthesia.
Absorption: IV administration results in complete bioavailability.
Distribution: Accumulates and may be slowly re-released from lipoid tissues; rapidly crosses the blood-brain barrier. Crosses the placenta.
Metabolism and Excretion: Mostly metabolized by the liver; some metabolism in kidneys and brain.
Half-life: 1.5–5 hr (increased in geriatric patients).
Time/action profile (anesthesia)
|IV||within 60 sec||unknown||5–7 min|
Contraindicated in: Hypersensitivity; Intra-arterial injection; Porphyria; Lactation: Lactation.
Use Cautiously in: Addison’s disease; Severe anemia; Severe CV or hepatic disease; Myxedema; Shock or hypotension; Pulmonary disease; Debilitated patients; Geriatric: Appears on Beers list. Geriatric patients are at increased risk for side effects (dose reduction recommended); Obstetric: Safety not established.
Adverse Reactions/Side Effects
Central nervous system
- seizures (life-threatening)
- emergence delirium
Ear, Eye, Nose, Throat
- apnea (life-threatening)
- laryngospasm (life-threatening)
- respiratory depression
- cardiorespiratory arrest (life-threatening)
- abdominal pain
- pain at IM site
- phlebitis at IV site
- muscle twitching
- shivering (most frequent)
- allergic reactions
Drug-Drug interactionAdditive CNS depression with alcohol, antihistamines, opioid analgesics, and sedative/hypnotics.See sedative interactions.St. John's wort may affect methohexital levels and effectiveness; avoid use.Concomitant use of kava, valerian, skullcap, chamomile, or hops can increase CNS depression.
Route/DosageAll doses must be individualized
Intravenous (Adults) Induction—1–1.5 mg/kg. Maintenance—20–40 mg q 4–7 min as intermittent doses or 3 mL of a 0.2% solution/min.
Intramuscular (Children >1 mo) Induction—6.6–10 mg/kg of a 5% solution.
Rectal (Children >1 mo) Induction—25 mg/kg using a 1% solution.
Availability (generic available)
Powder for injection: 500 mg, 2.5 g, 5 g
- Assess BP, ECG, heart rate, and respiratory status continuously throughout methohexital therapy. Methohexital should be used only by individuals qualified to administer anesthesia and experienced in endotracheal intubation. Equipment for this procedure should be immediately available. Apnea may occur immediately after IV injection, especially in the presence of opioid premedication.
- Monitor IV site carefully. Extravasation may cause pain, swelling, ulceration, and necrosis. Intra-arterial injection may cause arteritis, vasospasm, edema, thrombosis, and gangrene of the extremity. Overdose may occur from rapid injection (drop in BP, possibly to shock levels) or excessive or repeated injections (respiratory distress, laryngospasm, apnea).
Potential Nursing DiagnosesIneffective breathing pattern (Side Effects)
Risk for injury (Side Effects)
- Do not confuse Brevital (methohexital) with Brevibloc (esmolol).
- Dose is individualized according to depth of anesthesia desired; concurrent use of other medications and/or nitrous oxide; patient’s condition, age, weight, and sex.
- Geriatric: Geriatric patients may require smaller doses than young patients. Tolerance may develop with repeated use, such as for burns. Individuals tolerant to alcohol or barbiturates may require higher doses.
- Intravenous: Repeated doses or continuous infusion of methohexital may cause prolonged somnolence and respiratory and circulatory depression. If the patient requires a second anesthetic in the same day, reduction in the dose of methohexital may be required.
- Methohexital may be given in doses sufficient to produce deep surgical anesthesia, but such doses may cause dangerous respiratory and circulatory depression.
- Premedication with anticholinergics (atropine, glycopyrrolate) may be used to decrease mucous secretions. Opioid analgesics may be administered preoperatively to enhance the poor analgesic effects of methohexital. Preoperative medications should be given so that peak effect is attained shortly before induction of anesthesia. Muscle relaxants, if required, should be administered separately.
- Diluent: Do not use diluents containing bacteriostats. Dilute 500 mg vial with 50 mL of sterile water for injection (preferred), D5W, or 0.9% NaCl. Concentration: 10 mg/mL (1% solution). Solution should be freshly prepared and used within 24 hr of reconstitution. Refrigerate and keep sealed. Do not administer solution containing a precipitate.
- Rate: Induction dose is administered at a rate not to exceed 1 mL (10 mg) over 5 sec.
- Continuous Infusion: Diluent: To prepare a 1% (10 mg/mL) solution, reconstitute each 2.5-g vial with 15 mL or each 5-g vial with 30 mL of sterile water for injection (preferred), D5W, or 0.9% NaCl. Initial solution will be yellow. Further dilute the 2.5-g vial in 250 mL or the 5-g vial in 500 mL. Concentration: 10 mg/mL (1% solution). Solution should be used only if clear and colorless.
- Diluent: To prepare a 0.2% solution, dilute 500 mg in 250 mL of D5W or 0.9% NaCl. To avoid hypotonicity, do not dilute with sterile water. Concentration: 0.2% solution.
- Solution is stable for 24 hr.
- Rate: Anesthesia is maintained by intermittent injections every 4–7 min or by continuous infusion.
- Syringe Compatibility: propofol.
- Syringe Incompatibility: glycopyrrolate
- Y-Site Compatibility: acyclovir, aminocaproic acid, atenolol, bivalirudin, bleomycin, carboplatin, cisplatin, cyclophosphomide, cytarabine, dactinomycin, dexmedetomidine, doxacurium, etoposide, fludarabine, fluorouracil, hydromorphone, ifosfamide, methotrexate, milrinone, mitoxantrone, nesiritide, octreotide, paclitaxel, pancuronium, pantoprazole, tigecycline, tirofiban, vasopressin, vincristine, voriconazole
- Y-Site Incompatibility: doxorubicin, epirubicin, eptifibitide, etoposide phosphate, fenoldopam, gemtuzumab, idarubicin, irinotecan, mechlorethamine, ondanestron, oxytocin, rocuronium, vecuronium, vinorelbine
- Methohexital may cause psychomotor impairment for 24 hr after administration. Caution patient to avoid driving or other activities requiring alertness for 24 hr.
- Advise patient to avoid use of alcohol or other CNS depressants for 24 hr after anesthesia, unless directed by health care professional.
- Loss of consciousness.
- Maintenance of desired level of anesthesia without complications.