See boxed Warning.
As with all potent anesthetic agents and adjuncts, Brevital should be used only in hospital or ambulatory care settings that provide for continuous monitoring of respiratory (e.g. pulse oximetry) and cardiac function. Immediate availability of resuscitative drugs and age- and size-appropriate equipment for bag/valve/mask ventilation and intubation and personnel trained in their use and skilled in airway management should be assured. For deeply sedated patients, a designated individual other than the practitioner performing the procedure should be present to continuously monitor the patient.
Maintenance of a patent airway and adequacy of ventilation must be ensured during induction and maintenance of anesthesia with methohexital sodium solution. Laryngospasm is common during induction with all barbiturates and may be due to a combination of secretions and accentuated reflexes following induction or may result from painful stimuli during light anesthesia. Apnea/hypoventilation may be noted during induction, which may impair pulmonary ventilation; the duration of apnea may be longer than that produced by other barbiturate anesthetics. Cardiorespiratory arrest may occur.
This prescribing information describes intravenous use of methohexital sodium in adults. It also discusses intramuscular and rectal administration in pediatric patients older than one month. Although the published literature discusses intravenous administration in pediatric patients, the safety and effectiveness of intravenous administration of methohexital sodium in pediatric patients have not been established in well-controlled, prospective studies. (See PRECAUTIONS— Pediatric Use)
Seizures may be elicited in subjects with a previous history of convulsive activity, especially partial seizure disorders.
Because the liver is involved in demethylation and oxidation of methohexital and because barbiturates may enhance preexisting circulatory depression, severe hepatic dysfunction, severe cardiovascular instability, or a shock-like condition may be reason for selecting another induction agent.
Prolonged administration may result in cumulative effects, including extended somnolence, protracted unconsciousness, and respiratory and cardiovascular depression. Respiratory depression in the presence of an impaired airway may lead to hypoxia, cardiac arrest, and death.
The CNS-depressant effect of Brevital Sodium may be additive with that of other CNS depressants, including ethyl alcohol and propylene glycol.
DANGER OF INTRA-ARTERIAL INJECTION
Unintended intra-arterial injection of barbiturate solutions may be followed by the production of platelet aggregates and thrombosis, starting in arterioles distal to the site of injection. The resulting necrosis may lead to gangrene, which may require amputation. The first sign in conscious patients may be a complaint of fiery burning that roughly follows the distribution path of the injected artery; if noted, the injection should be stopped immediately and the situation reevaluated. Transient blanching may or may not be noted very early; blotchy cyanosis and dark discoloration may then be the first sign in anesthetized patients. There is no established treatment other than prevention. The following should be considered prior to injection:
- The extent of injury is related to concentration. Concentrations of 1% methohexital will usually suffice; higher concentrations should ordinarily be avoided.
- Check the infusion to ensure that the catheter is in the lumen of a vein before injection. Injection through a running intravenous infusion may enhance the possibility of detecting arterial placement; however, it should be remembered that the characteristic bright-red color of arterial blood is often altered by contact with drugs. The possibility of aberrant arteries should always be considered.
Postinjury arterial injection of vasodilators and/or arterial infusion of parenteral fluids are generally regarded to be of no value in altering outcome. Animal experiments and published individual case reports concerned with a variety of arteriolar irritants, including barbiturates, suggest that 1 or more of the following may be of benefit in reducing the area of necrosis:
- Arterial injection of heparin at the site of injury, followed by systemic anticoagulation.
- Sympathetic blockade (or brachial plexus blockade in the arm).
- Intra-arterial glucocorticoid injection at the site of injury, followed by systemic steroids.
- A case report (nonbarbiturate injury) suggests that intra-arterial urokinase may promote fibrinolysis, even if administered late in treatment.
If extravasation is noted during injection of methohexital, the injection should be discontinued until the situation is remedied. Local irritation may result from extravasation; subcutaneous swelling may also serve as a sign of arterial or periarterial placement of the catheter.
All routes of administration of Brevital Sodium are often associated with hiccups, coughing, and/or muscle twitching, which may also impair pulmonary ventilation. Following induction, temporary hypotension and tachycardia may occur.
Recovery from methohexital anesthesia is rapid and smooth. The incidence of postoperative nausea and vomiting is low if the drug is administered to fasting patients. Postanesthetic shivering has occurred in a few instances.
The usual precautions taken with any barbiturate anesthetic should be observed with Brevital Sodium. The drug should be used with caution in patients with asthma, obstructive pulmonary disease, severe hypertension or hypotension, myocardial disease, congestive heart failure, severe anemia, or extreme obesity.
Methohexital sodium should be used with extreme caution in patients in status asthmaticus. Caution should be exercised in debilitated patients or in those with impaired function of respiratory, circulatory, renal, hepatic, or endocrine systems.
Information for Patients
When appropriate, patients should be instructed as to the hazards of drowsiness that may follow use of Brevital Sodium. Outpatients should be released in the company of another individual, and no skilled activities, such as operating machinery or driving a motor vehicle, should be engaged in for 8 to 12 hours.
BSP and liver function studies may be influenced by administration of a single dose of barbiturates.
Prior chronic administration of barbiturates or phenytoin (e.g. for seizure disorder) appears to reduce the effectiveness of Brevital Sodium. Barbiturates may influence the metabolism of other concomitantly used drugs, such as phenytoin, halothane, anticoagulants, corticosteroids, ethyl alcohol, and propylene glycol-containing solutions.
Carcinogenesis, Mutagenesis, Impairment of Fertility
Studies in animals to evaluate the carcinogenic and mutagenic potential of Brevital Sodium have not been conducted. Reproduction studies in animals have revealed no evidence of impaired fertility.
Usage in Pregnancy
Pregnancy Category B
Reproduction studies have been performed in rabbits and rats at doses up to 4 and 7 times the human dose respectively and have revealed no evidence of harm to the fetus due to methohexital sodium. There are, however, no adequate and well-controlled studies in pregnant women. Because animal reproduction studies are not always predictive of human response, this drug should be used during pregnancy only if clearly needed.
Labor and Delivery
Brevital Sodium has been used in cesarean section delivery but, because of its solubility and lack of protein binding, it readily and rapidly traverses the placenta.
Caution should be exercised when Brevital Sodium is administered to a nursing woman.
The safety and effectiveness of methohexital sodium in pediatric patients below the age of 1 month have not been established. Seizures may be elicited in subjects with a previous history of convulsive activity, especially partial seizure disorders. Apnea has been reported following dosing with methohexital regardless of the route of administration used. Studies using methohexital sodium intravenously in pediatric patients have been reported in the published literature. This literature is not adequate to establish the safety and effectiveness of intravenous administration of methohexital sodium in pediatric patients. Due to a variety of limitations such as study design, biopharmaceutic issues, and the wide range of effects observed with similar doses of intravenous methohexital, additional studies of intravenous methohexital in pediatric patients are necessary before this route can be recommended in pediatric patients. (See WARNINGS)
Clinical studies of Brevital did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. Other reported clinical experience has not identified differences in responses between the elderly and younger patients. Elderly subjects may commonly have conditions in which methohexital should be used cautiously such as obstructive pulmonary disease, severe hypertension or hypotension, preexisting circulatory depression, myocardial disease, congestive heart failure, or severe anemia. Caution should be exercised in debilitated patients or in those with impaired function of respiratory, circulatory, renal, hepatic, or endocrine systems (see WARNINGS, PRECAUTIONS and ADVERSE REACTIONS). Barbiturates may influence the metabolism of other concomitantly used drugs that are commonly taken by the elderly, such as anticoagulants and corticosteroids. In general, dose selection for an elderly patient should be cautious, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy (see PRECAUTIONS-Drug Interactions).