Pentobarbital

Nembutal, Nembutal Sodium

WHAT IS Pentobarbital?

Pentobarbital is in a class of drugs called barbiturates (bar bi TURE ates). Pentobarbital depresses the activity of your brain and nervous system.

Pentobarbital is used to treat insomnia (for up to 2 weeks) and to induce sleep before surgery.

Pentobarbital may also be used for purposes other than those listed in this medication guide.

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What is the most important information I should know about pentobarbital?

Call your doctor immediately if you develop a fever, a sore throat, sores in your mouth, broken blood vessels under your skin, or easy bruising or bleeding. These could be early signs of a serious side effect.
Use caution when driving, operating machinery, or performing other hazardous activities. Pentobarbital will cause drowsiness. If you experience drowsiness, avoid these activities. Do not drink alcohol or take other sleep medicines, antihistamines, narcotic pain relievers, or other drugs that also cause drowsiness unless your doctor approves. Dangerous sedation could result. Pentobarbital may decrease the effectiveness of birth control pills. Use a second method of birth control while taking pentobarbital to prevent pregnancy.

Warnings/Precautions

Tolerance to hypnotic effect can occur; do not use for >2 weeks to treat insomnia. Potential for drug dependency exists, abrupt cessation may precipitate withdrawal, including status epilepticus in epileptic patients. Do not administer to patients in acute pain. Use caution in elderly, debilitated, renally impaired, hepatic dysfunction, or pediatric patients. May cause paradoxical responses, including agitation and hyperactivity, particularly in acute pain and pediatric patients. Use with caution in patients with depression or suicidal tendencies, or in patients with a history of drug abuse. Tolerance, psychological and physical dependence may occur with prolonged use.

May cause CNS depression, which may impair physical or mental abilities. Patients must be cautioned about performing tasks which require mental alertness (eg, operating machinery or driving). Effects with other sedative drugs or ethanol may be potentiated. Use of this agent as a hypnotic in the elderly is not recommended due to its long half-life and potential for physical and psychological dependence.

May cause respiratory depression or hypotension, particularly when administered intravenously. Use with caution in hemodynamically unstable patients or patients with respiratory disease. High doses (loading doses of 15-35 mg/kg given over 1-2 hours) have been utilized to induce pentobarbital coma, but these higher doses often cause hypotension requiring vasopressor therapy.

Drug Interactions

Induces CYP2A6 (strong), 3A4 (strong)

Acetaminophen: Barbiturates may enhance the hepatotoxic potential of acetaminophen overdoses

Antiarrhythmics: Barbiturates may increase the metabolism of antiarrhythmics, decreasing their clinical effect; includes disopyramide, propafenone, and quinidine

Anticonvulsants: Barbiturates may increase the metabolism of anticonvulsants; includes ethosuximide, felbamate (possibly), lamotrigine, phenytoin, tiagabine, topiramate, and zonisamide; does not appear to affect gabapentin or levetiracetam

Antineoplastics: Limited evidence suggests that enzyme-inducing anticonvulsant therapy may reduce the effectiveness of some chemotherapy regimens (specifically in ALL); teniposide and methotrexate may be cleared more rapidly in these patients

Antipsychotics: Barbiturates may enhance the metabolism (decrease the efficacy) of antipsychotics; monitor for altered response; dose adjustment may be needed

Beta-blockers: Metabolism of beta-blockers may be increased and clinical effect decreased; atenolol and nadolol are unlikely to interact given their renal elimination

Calcium channel blockers: Barbiturates may enhance the metabolism of calcium channel blockers, decreasing their clinical effect

Chloramphenicol: Barbiturates may increase the metabolism of chloramphenicol and chloramphenicol may inhibit barbiturate metabolism; monitor for altered response

Cimetidine: Barbiturates may enhance the metabolism of cimetidine, decreasing its clinical effect

CNS depressants: Sedative effects and/or respiratory depression with barbiturates may be additive with other CNS depressants; monitor for increased effect; includes ethanol, sedatives, antidepressants, narcotic analgesics, and benzodiazepines

Corticosteroids: Barbiturates may enhance the metabolism of corticosteroids, decreasing their clinical effect

Cyclosporine: Levels may be decreased by barbiturates; monitor

CYP2A6 substrates: Pentobarbital may decrease the levels/effects of CYP2A6 substrates. Example substrates include ifosfamide and rifampin.

CYP3A4 substrates: Pentobarbital may decrease the levels/effects of CYP3A4 substrates. Example substrates include benzodiazepines, calcium channel blockers, clarithromycin, cyclosporine, erythromycin, estrogens, mirtazapine, nateglinide, nefazodone, nevirapine, protease inhibitors, tacrolimus, and venlafaxine.

Doxycycline: Barbiturates may enhance the metabolism of doxycycline, decreasing its clinical effect; higher dosages may be required

Estrogens: Barbiturates may increase the metabolism of estrogens and reduce their efficacy

Felbamate may inhibit the metabolism of barbiturates and barbiturates may increase the metabolism of felbamate

Griseofulvin: Barbiturates may impair the absorption of griseofulvin, and griseofulvin metabolism may be increased by barbiturates, decreasing clinical effect

Guanfacine: Effect may be decreased by barbiturates

Immunosuppressants: Barbiturates may enhance the metabolism of immunosuppressants, decreasing its clinical effect; includes both cyclosporine and tacrolimus

Loop diuretics: Metabolism may be increased and clinical effects decreased; established for furosemide, effect with other loop diuretics not established

MAO inhibitors: Metabolism of barbiturates may be inhibited, increasing clinical effect or toxicity of the barbiturates

Methadone: Barbiturates may enhance the metabolism of methadone resulting in methadone withdrawal

Methoxyflurane: Barbiturates may enhance the nephrotoxic effects of methoxyflurane

Oral contraceptives: Barbiturates may enhance the metabolism of oral contraceptives, decreasing their clinical effect; an alternative method of contraception should be considered

Theophylline: Barbiturates may increase metabolism of theophylline derivatives and decrease their clinical effect

Tricyclic antidepressants: Barbiturates may increase metabolism of tricyclic antidepressants and decrease their clinical effect; sedative effects may be additive

Valproic acid: Metabolism of barbiturates may be inhibited by valproic acid; monitor for excessive sedation; a dose reduction may be needed

Warfarin: Barbiturates inhibit the hypoprothrombinemic effects of oral anticoagulants via increased metabolism; this combination should generally be avoided

Who should not take pentobarbital?

Do not take pentobarbital if you have

• porphyria
• liver disease,
• kidney disease, or
• severe respiratory disease such as severe asthma or severe chronic obstructive pulmonary disorder (COPD).

Before taking this medication, tell your doctor if you have ever had a drug or alcohol addiction in the past. Pentobarbital is habit forming, which means that you can become addicted to it. Pentobarbital is in the FDA pregnancy category D. This means that it is known to harm an unborn baby. Do not take pentobarbital if you are pregnant. Pentobarbital passes into breast milk and could affect a nursing infant. Do not take pentobarbital without first talking to your doctor if you are breast-feeding a baby.

Pentobarbital may cause excitement, irritability, aggression, depression, or confusion-- particularly in children and in adults over 60 years of age. Lower doses and close monitoring may be necessary.

How should I take pentobarbital?

Take pentobarbital exactly as directed by your doctor. If you do not understand the directions on your prescription bottle, ask your pharmacist, nurse, or doctor to explain them to you. Take each dose with a full glass of water.

The suppositories are for rectal use. Ask your pharmacist, nurse, or doctor for instructions if you do not know how to insert a suppository.

To treat insomnia, pentobarbital is usually taken just before bedtime. Take your dose when you are ready to get into bed, or not long before, so that if you become sleepy, you will not fall or become confused and accidentally injure yourself. Pentobarbital should not be used for longer than 2 weeks to treat insomnia.

To cause sedation, pentobarbital may be taken several times a day at regular intervals, or shortly before surgery.
Do not increase your dosage of this medicine without the approval of your doctor. If your symptoms are not being adequately treated, talk to your doctor. Store pentobarbital at room temperature away from moisture and heat.

Pentobarbital side effects

If you experience any of the following serious side effects, stop taking pentobarbital and seek emergency medical attention or call your doctor immediately:

• an allergic reaction (difficulty breathing; closing of your throat; swelling of your lips, tongue, or face; or hives);
• a fever or a sore throat;
• sores in your mouth;
• broken blood vessels under your skin; or
• easy bruising or bleeding.

Other, less serious side effects may be more likely to occur. Continue to take pentobarbital and talk to your doctor if you experience

• drowsiness or dizziness;
• confusion;
• agitation, irritability, or excitability;
• nightmares, nervousness, or anxiety;
• headache; or
• "hangover" effect (drowsiness the day after a dose).