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Pharmacologic class: Barbiturate
Therapeutic class: Sedative-hypnotic, anticonvulsant
Controlled substance schedule II
Pregnancy risk category D
Depresses sensory cortex, decreases motor activity, and alters cerebellar function; may interfere with nerve impulse transmission in brain
Injection: 50 mg/ml in 2-ml prefilled syringes
Indications and dosages
➣ Preoperative sedation
Adults: Initially, 150 to 200 mg I.M., or 100 mg I.V.
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.
• 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
Use cautiously in:
• hepatic or renal impairment, increased risk for suicide, alcohol use
• history of drug addiction
• labor and delivery
• elderly or debilitated patients.
☞ 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.
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
Skin: rash, urticaria, exfoliative dermatitis
Other: phlebitis at I.V. site, physical or psychological drug dependence, fever, hypersensitivity reactions including angioedema
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. Sulfobromoph-thalein: 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
☞ 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.
• 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.