Pentobarbital

Brand names: Nembutal
Drug class: Antineoplastic Agents

Usage of Pentobarbital

Insomnia

Short-term treatment of insomnia (i.e., ≤2 weeks duration); decreased effectiveness for sleep induction and maintenance after 2 weeks.

Has been used for routine sedation. However, barbiturates used infrequently for this indication since there are few clinical situations in which oral barbiturates provide a safety or efficacy advantage over nonbarbiturate sedatives/hypnotics.

Surgery and Preanesthesia

Preoperatively, to produce sedation and relieve anxiety.

Provide basal hypnosis for general, spinal, or regional anesthesia, or to facilitate intubation procedures.

Seizure Disorders

Alternate therapy to control status epilepticus or acute seizure episodes resulting from meningitis, poisons, eclampsia, alcohol withdrawal, tetanus, or chorea.

IV Diazepam generally considered drug of choice for termination of status epilepticus.

Drug Withdrawal

Withdrawal of barbiturate or nonbarbiturate hypnotics in physically dependent patients.

Agitated Behavior

Has been used to control acute episodes of agitated behavior in psychoses† [off-label]; however, little value in long-term management of psychoses.

Coma Induction

Has been used in high doses to induce coma in the management of cerebral ischemia† [off-label] and increased intracranial pressure† [off-label] associated with head trauma, stroke, Reye’s syndrome, cardiac arrest, asphyxiation, or drowning.

Has been used to ameliorate or prevent sequelae associated with cerebral ischemia during neurosurgical procedures† [off-label] that require long periods of cerebral hypoxia.

Relate drugs

How to use Pentobarbital

General

  • Adjust dosage carefully and slowly according to individual requirements and response.
  • Following chronic administration, withdraw pentobarbital slowly to avoid the possibility of precipitating withdrawal symptoms if the patient is physically dependent on the drug.
  • To prevent rebound in rapid eye movement (REM) sleep, withdrawal of a single therapeutic dose over 5 or 6 days (e.g., reducing dosage from 3 to 2 doses daily for 1 week) has been recommended when barbiturates are discontinued following prolonged use.

    • Insomnia

  • Do not administer for periods >2 weeks.

    • Administration

    Administer by IM or slow IV injection.

    IV Administration

    For solution and drug compatibility information, see Compatibility under Stability.

    Reserve IV administration for inducing anesthesia or emergency treatment of acute seizure episodes or acute episodes of agitated behavior in psychoses. (See Seizure Disordersand also Agitated Behavior under Uses.)

    Usually administered in a concentration of 50 mg/mL.

    Must be administered by slow IV injection and in fractional doses to allow for adequate time for pentobarbital to distribute into CNS. A time interval of ≥1 minute is required to determine the full effect of an IV dose.

    Administer under close supervision and in a setting where vital signs can be monitored; BP, respiration, and cardiac function maintained; and equipment for resuscitation and artificial ventilation are readily available. (See Respiratory and Cardiovascular Effects under Cautions.)

    Avoid intra-arterial and extravascular injection. (See Intra-arterial Injection under Cautions.)

    Rate of Administration

    Do not exceed 50 mg/minute. (See Respiratory and Cardiovascular Effects under Cautions.)

    IM Administration

    Administer by deep IM injection into a large muscle.

    Administer a maximum volume of 5 mL at any one site to avoid tissue irritation.

    After administration of large hypnotic doses, observe patient closely for 20–30 minutes and monitor vital signs to ensure narcosis will not be excessive.

    Dosage

    Available as pentobarbital sodium; dosage expressed in terms of the salt.

    IV dosage generally determined by patient’s reaction to slow administration of the drug.

    A time interval of >1 minute required to determine the full effect of an IV dose.

    Pediatric Patients

    Insomnia IM

    2–6 mg/kg or 125 mg/m2 as a single dose (maximum 100 mg).

    Surgery and Preanesthesia IM

    Usually, approximately 5 mg/kg.

    IV

    Initially, usually 50 mg. If necessary, administer subsequent doses after >1 minute.

    Seizure Disorders IV

    Initially, usually 50 mg. If necessary, administer subsequent doses after >1 minute.

    Agitated Behavior† [off-label] IV

    Initially, usually 50 mg. If necessary, administer subsequent doses after >1 minute.

    Adults

    Insomnia IM

    150–200 mg as a single dose.

    IV

    Initially, usually 100 mg for an adult weighing 70 kg. After >1 minute, if necessary, administer additional small doses up to a total of 200–500 mg.

    Surgery and Preanesthesia IM

    150–200 mg as a single dose.

    Seizures IV

    Initially, usually 100 mg. After >1 minute, if necessary, administer additional small doses up to a total of 200–500 mg.

    Administer minimum dosage to avoid compounding the CNS and respiratory depression which may follow seizures. (See CNS Depression and also Respiratory and Cardiovascular Effects, under Cautions.)

    Drug Withdrawal IM

    Establish a stabilizing dose (generally adminstered at 6-hour intervals), then decrease the daily dose by no more than 100 mg per day. Severely dependent patients can usually be withdrawn from barbiturates in 14–21 days.

    Agitated Behavior† IV

    Initially, usually 100 mg. After >1 minute, if necessary, administer additional small doses up to a total of 200–500 mg.

    Prescribing Limits

    Pediatric Patients

    Insomnia IM

    Maximum 100 mg daily.

    Adults

    IV

    Maximum 200–500 mg.

    Special Populations

    Hepatic Impairment

    Dosage reduction recommended.

    Renal Impairment

    Dosage reduction recommended.

    Geriatric Patients

    Dosage reduction recommended.

    Debilitated Patients

    Dosage reduction recommended.

    Warnings

    Contraindications

  • Known hypersensitivity to any barbiturates.
  • History of manifest or latent porphyria. (See Porphyria under Cautions.)
  • Bronchopneumonia or other severe pulmonary insufficiency.

    • Warnings/Precautions

    Warnings

    Pain Reaction

    Potential for paradoxical excitement and/or euphoria, restlessness, or delirium in patients with severe pain. Barbiturates could mask important symptoms in patients with acute or chronic pain. Use with caution in such patients. Should not be used in the presence of uncontrolled pain.

    Abuse Potential

    Possible tolerance, psychological dependence, and physical dependence following prolonged administration.

    Withdrawal Effects

    Abrupt cessation after prolonged use in dependent individuals may result in withdrawal symptoms (e.g., delirium, convulsions) and potentially be fatal. Drug must be withdrawn gradually in patients receiving excessive dosages over extended periods of time.

    CNS Depression

    Performance of activities requiring mental alertness or physical coordination may be impaired.

    Concurrent use of other CNS depressants may potentiate CNS depression. (See Specific Drugs under Interactions.)

    Respiratory and Cardiovascular Effects

    Possible respiratory depression, apnea, laryngospasm, or vasodilation and hypotension, particularly if pentobarbital is administered IV too rapidly. Administer slowly; personnel and equipment should be readily available for administration of artificial respiration.

    Fetal/Neonatal Morbidity

    May cause fetal harm. If used during pregnancy or if patient becomes pregnant, apprise of potential fetal hazard.

    Retrospective, case-controlled studies indicate an association between maternal ingestion of barbiturates and a higher than expected incidence of fetal abnormalities.

    Based on animal data, repeated or prolonged use of general anesthetics and sedation drugs, including pentobarbital, during the third trimester of pregnancy may result in adverse neurodevelopmental effects in the fetus. (See Pediatric Use under Cautions and also see Advice to Patients.)

    Barbiturates have caused postpartum hemorrhage and hemorrhagic disease in neonates; readily reversible with vitamin K therapy.

    Possible withdrawal symptoms in neonates born to women who received barbiturates throughout the last trimester of pregnancy. Premature neonates are particularly susceptible to the depressant effects of barbiturates.

    Porphyria

    Potential exacerbation of acute intermittent porphyria or porphyria variegata. (See Contraindications under Cautions.)

    Complex Sleep-related Behaviors

    Potential risk of complex sleep-related behaviors such as sleep-driving (i.e., driving while not fully awake after ingesting a sedative-hypnotic drug, with no memory of the event), making phone calls, or preparing and eating food, while asleep.

    Sensitivity Reactions

    Potential risk of anaphylaxis and angioedema; may occur as early as with the first dose of drug.

    Dermatologic Effects and Hypersensitivity Reactions

    Exfoliative dermatitis (e.g., Stevens-Johnson syndrome), sometimes fatal, reported rarely. Because skin eruptions can precede potentially fatal reactions, discontinue pentobarbital whenever dermatologic reactions occur.

    General Precautions

    Intra-arterial Injection

    Inadvertent intra-arterial administration can cause local reactions varying in severity from transient pain to gangrene. Inadvertent extravascular injection may cause local tissue damage and result in necrosis.

    Discontinue injection if the patient complains of pain in limb.

    Suicide

    Use with caution, if at all, in patients with depression or suicidal tendencies.

    Concomitant Diseases

    Use parenterally with caution in patients with hypertension, hypotension, pulmonary or cardiovascular disease, or shock.

    Specific Populations

    Pregnancy

    Category D. (See Fetal/Neonatal Morbidity under Cautions.)

    Lactation

    Distributed into milk; use with caution.

    Pediatric Use

    Repeated or prolonged use of general anesthetics and sedation drugs, including pentobarbital, in children <3 years of age or during the third trimester of pregnancy may adversely affect neurodevelopment. In animals, use for >3 hours of anesthetic and sedation drugs that block N-methyl-d-aspartic acid (NMDA) receptors and/or potentiate GABA activity leads to widespread neuronal apoptosis in the brain and long-term deficits in cognition and behavior; clinical relevance to humans is unknown.

    Some evidence suggests similar deficits may occur in children following repeated or prolonged exposure to anesthesia early in life. Some evidence also indicates that a single, relatively brief exposure to general anesthesia in generally healthy children is unlikely to cause clinically detectable deficits in global cognitive function or serious behavioral disorders. Most studies to date have substantial limitations; further research needed to fully characterize effects, particularly for prolonged or repeated exposures and in more vulnerable populations (e.g., less healthy children).

    Consider benefits and potential risks when determining the timing of elective procedures requiring anesthesia. FDA states that medically necessary procedures should not be delayed or avoided. (See Advice to Patients.)

    Geriatric Use

    Possible increased sensitivity to barbiturates. Geriatric patients may frequently react to barbiturates with excitement, confusion, or depression.

    Debilitated Patients

    Possible increased sensitivity to barbiturates. Debilitated patients may frequently react to barbiturates with excitement, confusion, or depression.

    Hepatic Impairment

    Use with caution; should not be used in patients with marked hepatic impairment, including patients with premonitory signs of hepatic coma.

    Common Adverse Effects

    Residual sedation, drowsiness, lethargy, vertigo, nausea, vomiting, headache.

    What other drugs will affect Pentobarbital

    Metabolized by hepatic microsomal enzymes. Induces hepatic microsomal enzymes.

    Specific Drugs

    Drug

    Interaction

    Comments

    Anticoagulants, oral (e.g., warfarin)

    Possible decreased plasma warfarin concentrations

    Adjust anticoagulant dosage as necessary, especially upon initiation or discontinuance of pentobarbital

    CNS depressants (e.g., sedatives, hypnotics, antihistamines, tranquilizers, alcohol)

    Possible additive depressant effects

    Contraceptives, oral

    Possible enhanced metabolism of estrogenic and progestinic components; potential for decreased oral contraceptive effectiveness and increased risk of pregnancy with pentobarbital pretreatment or concurrent therapy

    Consider alternate methods of contraception

    Corticosteroids

    Possible increased corticosteroid metabolism

    Dosage adjustment of corticosteroid may be required; closely monitor patients (especially asthmatics) receiving corticosteroids when pentobarbital is initiated

    Doxycycline

    Possible decreased half-life of doxycycline; effect may persist up to 2 weeks after discontinuance of pentobarbital

    If possible, avoid concomitant administration; if administered concomitantly, monitor clinical response to doxycycline

    Griseofulvin

    Possible decreased griseofulvin absorption, resulting in decreased blood concentrations

    Avoid concomitant administration; if concomitant therapy is necessary, administration of griseofulvin in 3 divided doses daily may improve absorption

    Monitor blood griseofulvin concentrations and increase dosage, if necessary

    MAO inhibitors

    Possible prolongation of pentobarbital effects

    Dose adjustment of pentobarbital may be required

    Phenytoin

    Increased, decreased, or no change in plasma phenytoin concentrations reported

    Monitor plasma concentrations of phenytoin and pentobarbital; adjust dosages as necessary

    Valproic acid

    Possible increased plasma pentobarbital concentrations

    Monitor plasma pentobarbital concentrations and adjust dosage as needed

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