pentobarbital sodium

pen·to·bar·bi·tal sodium (pnt-bärb-tôl, -tl)

n.

A white crystalline or powdery barbiturate used as a hypnotic, sedative, and anticonvulsive drug. Also called pentobarbitone.

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pentobarbital sodium

Nembutal Sodium

Pharmacologic class: Barbiturate

Therapeutic class: Sedative-hypnotic, anticonvulsant

Controlled substance schedule II

Pregnancy risk category D

Action

Depresses sensory cortex, decreases motor activity, and alters cerebellar function; may interfere with nerve impulse transmission in brain

Availability

Capsules: 100 mg

Elixir: 20 mg/5 ml

Injection: 50 mg/ml in 2-ml prefilled syringes

Suppositories: 30 mg, 120 mg, 200 mg

⊘Indications and dosages

➣ Sedation

Adults: 20 to 30 mg P.O. three to four times daily. Alternatively, 120 to 200 mg P.R. as a single dose.

Children: 2 to 6 mg/kg P.O. daily in divided doses; maximum of 100 mg/dose daily.

Alternatively, for P.R. dosing -

Children ages 12 to 14 weighing 36.4 to 50 kg (80 to 110 lb): 60 or 120 mg P.R.

Children ages 5 to 12 weighing 18.2 to 36.4 kg (40 to 80 lb): 60 mg P.R.

Children ages 1 to 4 weighing 9 to 18.2 kg (20 to 40 lb): 30 or 60 mg P.R.

Children ages 2 months to 1 year weighing 4.5 to 9 kg (10 to 20 lb): 30 mg P.R.

➣ Preoperative sedation

Adults: Initially, 100 mg P.O., 150 to 200 mg I.M., or 100 mg I.V.

➣ Seizures

Adults: Initially, 100 mg. I.V.; may give additional doses after 1 minute. Maximum dosage is 500 mg.

Children: Initially, 50 mg. I.V.; may give additional doses until desired response occurs. Don't exceed 100 mg/dose.

Contraindications

• Hypersensitivity to drug or other barbiturates
• Nephritis (with large doses)
• Severe hepatic impairment
• Severe respiratory disease with dyspnea or obstruction
• Manifest or latent porphyria
• History of sedative-hypnotic abuse
• Subcutaneous or intra-arterial administration

Precautions

Use cautiously in:
• hepatic or renal impairment, increased risk for suicide, alcohol use
• history of drug addiction
• labor and delivery
• elderly or debilitated patients.

Administration

☞ When giving I.V., make sure resuscitation equipment is available.
• Give I.V. by direct injection no faster than 50 mg/minute.
• Inject I.M. deep into large muscle mass.
☞ Don't give by subcutaneous or intra-arterial routes, because severe reactions (such as tissue necrosis and gangrene) may occur.
• Know that drug is for short-term use only, losing efficacy after about 2 weeks.
• Be aware that rectal suppositories are used when P.O. or parenteral administration isn't undesirable.
• Don't divide rectal suppositories.

Route	Onset	Peak	Duration
P.O.	15-60 min	3-4 hr	3-4 hr
I.V.	Immediate	1 min	3-4 hr
I.M.	10-25 min	Unknown	3-4 hr
Rectal	20-60 min	Unknown	3-4 hr

Adverse reactions

CNS: drowsiness, agitation, confusion, hyperkinesia, ataxia, nightmares, nervousness, hallucinations, insomnia, anxiety, abnormal thinking

CV: hypotension, syncope, bradycardia (all with I.V. use)

GI: nausea, vomiting, constipation

Hepatic: hepatic damage

Musculoskeletal: joint pain, myalgia, neuralgia

Respiratory: laryngospasm (with I.V. use), bronchospasm, respiratory depression

Skin: rash, urticaria, exfoliative dermatitis

Other: phlebitis at I.V. site, physical or psychological drug dependence, fever, hypersensitivity reactions including angioedema

Interactions

Drug-drug. Acetaminophen: increased risk of hepatotoxicity

Activated charcoal: decreased pentobarbital absorption

Anticoagulants, beta-adrenergic blockers (except timolol), carbamazepine, clonazepam, corticosteroids, digoxin, doxorubicin, doxycycline, felodipine, fenoprofen, griseofulvin, hormonal contraceptives, metronidazole, quinidine, theophylline, verapamil: decreased efficacy of these drugs

Antihistamines (first-generation), opioids, other sedative-hypnotics: additive CNS depression

Chloramphenicol, hydantoins, narcotics: increased or decreased effects of either drug

Divalproex, MAO inhibitors, valproic acid: decreased pentobarbital metabolism, increased sedation

Rifampin: increased pentobarbital metabolism and decreased effects

Drug-diagnostic tests. Sulfobromophthalein: false increase

Drug-herbs. Chamomile, hops, kava, valerian, or skullcap: increased CNS depression

St. John's wort: decreased pentobarbital effects

Drug-behaviors. Alcohol use: increased sedation, additive CNS depression

Patient monitoring

☞ Closely monitor blood pressure and heart and respiratory rates. Watch for evidence of respiratory depression.
• Monitor neurologic status before and during therapy.
• Assess CBC and kidney and liver function tests.
• In long-term therapy, monitor patient for signs of drug dependence.

Patient teaching

• Instruct patient to take exactly as prescribed.
• Tell patient that increasing dosage without prescriber's approval may lead to dependence.
• Advise patient to avoid other CNS depressants, alcohol, and herbs.
• Caution patient to avoid driving and other hazardous activities.
• Advise patient taking hormonal contraceptives to use alternate birth-control method during therapy.
• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs, tests, herbs, and behaviors mentioned above.