methohexital (Rx)

Frequency Not Defined

Hiccups, coughing, muscle twitching & laryngospasm, which may impair pulmonary ventilation

Respiratory depression, apnea, dyspnea, cardiorespiratory arrest (which may occur in association with seizures), or hypotension may occur

Circulatory depression, peripheral vasculatory collapse, bronchospasm, postanesthetic shivering, salivation, skeletal muscle hyperactivity (twitching to convulsive-like movements), seizures, restlessness, anxiety (especially in the presence of postop pain), headache, nausea, vomiting, abd pain, & emergence delirium may also occur

Acute allergic reactions including erythema, pruritus, urticaria, rhinitis, hypotension, dyspnea, anxiety, restlessness, abdominal pain & peripheral vascular collapse have been reported

Thrombophlebitis, injection site pain, & injury to nerves adjacent to injection site

Extravasation may cause local irritation manifested as pain, swelling, ulceration, & necrosis

Contraindications

Porphyria

Known hypersensitivity to barbiturates

Relative: cardiovascular disease, hypotension, respiratory disease

Cautions

Severe anemia, extreme obesity, debilitated patients

Renal/hepatic/endocrine/circulatory dysfunction, obstructive pulmonary dz, severe HTN, status asthmaticus

Rapid bolus doses will increase cardiorespiratory effects including laryngospasm, apnea, hypotension, myocardial depression, cardiovascular collapse

Mild sedation may persist 8-12 hr

Patients should be instructed on discharge not to drive or operate heavy machinery

General anesthetics and sedation drugs in young children and pregnant women

• Brain development

  • Prolonged or repeated exposure may result in negative effects on fetal or young children’s brain development
  • Caution with use during surgeries or procedures in children younger than 3 yr or in pregnant women during their third trimester
  • Administration of anesthetic and sedation drugs that block NMDA receptors and/or potentiate GABA activity increase neuronal apoptosis in developing brain and result in long-term cognitive deficits when used for longer than 3 hours; assess the risk:benefit ratio in these populations, especially for prolonged procedures (ie, >3 hr) or multiple procedures

Pregnancy

There are no adequate and well-controlled studies in pregnant women; published studies in pregnant primates demonstrate that administration of anesthetic and sedation drugs that block NMDA receptors and/or potentiate GABA activity during the period of peak brain development increases neuronal apoptosis in the developing brain of the offspring when used for longer than 3 hours; clinical significance not clear; however, studies in juvenile animals suggest neuroapoptosis correlates with long-term cognitive deficits

Lactation

Excreted in breast milk; use by nursing mothers should be evaluated carefully

Pregnancy Categories

A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.

B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.

C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.

D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.

X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.

NA: Information not available.

Mechanism of Action

Ultra short-acting anesthetic barbiturate; no muscle relaxant activity

Pharmacokinetics

Half-Life: 3-6 hr

Onset: Immediate (IV); 2-10 min (IM); 5-15 min (PR)

Duration: 10-20 min (IV); 45 min (PR)

Metabolism: Hepatically conjugated to inactive metabolites; slow

Excretion: Urine; trace amounts of drug &/or metabolites also excreted in feces & sweat

IV Compatibilities

Solution: D5/LR, D5W in NS, D5W, LR, NS

Additive: chlorpromazine, hydralazine, kanamycin, lidocaine, mechlorethamine, methyldopate, prochlorperazine, promazine, promethazine, streptomycin

Syringe: glycopyrrolate

IV Administration

Do not use diluents containing bacteriostats

Soln should be clear or colorless or it should not be used

Administer by injection or infusion, in concentration no higher than 1%

Avoid intraarterial injection & extravasation

Storage

Store at controlled room temp