Dosing and uses of Amytal Sodium (amobarbital)
Adult dosage forms and strengths
powder for injection: Schedule II
- 500mg
Sedative
30-50 mg IV q8-12hr
Hypnotic
Used as a hypnotic, for short-term treatment of insomnia; effectiveness for sleep induction and sleep maintenance is lost after 2 weeks
65-200 mg IV qHs
Pediatric dosage forms and strengths
powder for injection: Schedule II
- 500mg
Sedative
<6 years: Safety and effectiveness not established
6-12 years: 65 mg-500 mg IV/Im
>12 years: 30-50 mg IV q8-12hr
Hypnotic
Used as a hypnotic, for short-term treatment of insomnia; effectiveness for sleep induction and sleep maintenance is lost after 2 weeks
<6 years: Safety and effectiveness not established
6-12 years: 2-3 mg/kg; not to exceed 500 mg IV/Im
>12 years: 65-200 mg IV qHs
Geriatric dosage forms and strengths
Reduce dose in the elderly or debilitated because these patients may be more sensitive to barbiturates
Elderly and debilitated patients may react with marked excitement, depression, or confusion
Amytal Sodium (amobarbital) adverse (side) effects
1-10%
Somnolence
<1%
Nervous system: agitation, confusion, hyperkinesia, ataxia, CNS depression, nightmares, nervousness, psychiatric disturbance, hallucinations, insomnia, anxiety, dizziness, abnormality in thinking
Cardiovascular system: Bradycardia, hypotension, syncope
Respiratory system: apnea, hypoventilation, postoperative atelectasis
Digestive system: Constipation, vomiting, nausea
Other adverse effects: Headache, injection site reactions, hypersensitivity reactions, fever, liver damage, megaloblastic anemia following chronic phenobarbital use
Warnings
Contradindications
Hypersensitivity
Patients with history of manifest or latent porphyria
Significant impairment of liver function
Respiratory disease in which dyspnea or obstruction is evident
Cautions
Habit forming; tolerance and psychological dependence may occur with continued use
Caution in patients that are mentally depressed, have suicide ideation or history of drug abuse and hepatic damage
Rapid administration may cause respiratory depression, apnea, laryngospasm, or vasodilatation with decrease in blood pressure
Parenteral solutions of barbiturates are highly alkaline; care should be taken to avoid perivascular extravasation or intra-arterial injection
Amobarbital may diminish systemic effects of exogenous and endogenous corticosteroids. Administer with caution to patients with borderline hypoadrenal function, regardless of whether it is of pituitary or of primary adrenal origin
Possible impairment of mental and/or physical abilities required for the performance of potentially hazardous tasks, such as driving a car or operating machinery
Concurrent use of barbiturates with other CNS depressants (eg, alcohol, narcotics, tranquilizers, antihistamines) may result in increased CNS-depressant effects
Extravascular injection may cause local tissue damage with subsequent necrosis; consequences of intra-arterial injection may vary from transient pain to gangrene of the limb; any complaint of pain in the limb warrants stopping the injection
Pregnancy and lactation
Pregnancy category: d
Lactation: small amounts of barbiturates are excreted in the milk; use caution
Pregnancy categories
A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.
B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.
C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.
D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.
X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.
NA: Information not available.
Pharmacology of Amytal Sodium (amobarbital)
Mechanism of action
Depress the sensory cortex by interfering with transmission of impulses from thalamus. This results in decreased motor activity, altered cerebellar function, drowsiness, sedation, and hypnosis
Onset of Action
Within 5 minutes
Metabolism
Primarily hepatic via microsomal enzymes
Elimination
Half-Life: 15-40 hours in adults (mean 25 hours)
Excretion: feces, urine
Administration
IV Administration
Slow IV injection is essential; observe patients carefully during administration
Blood pressure, respiration, and cardiac function must be maintained, vital signs be recorded and equipment for resuscitation and artificial ventilation be available
The rate of IV injection for adults should not exceed 50 mg/min to prevent sleep or sudden respiratory depression
Final dosage is determined largely by the patient’s reaction to the slow administration of the drug
IM Administration
IM injection of the sodium salts of barbiturates should be made deeply into a large muscle
Average IM dose ranges from 65 mg-500 mg; volume of 5 mL (irrespective of concentration) should not be exceeded at any one site because of possible tissue irritation
Twenty percent solutions may be used so that a small volume can contain a large dose; monitor vital signs after IM injection of hypnotic dose
Superficial IM or subcutaneous injections may be painful and may produce sterile abscesses or sloughs
