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Pronunciation |
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(am
oh BAR bi
tal) |
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U.S. Brand
Names |
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Amytal® |
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Generic
Available |
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Yes: Capsule |
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Canadian Brand
Names |
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Amobarbital; Novambarb® |
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Synonyms |
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Amylobarbitone |
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Pharmacological Index |
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Barbiturate |
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Use |
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Oral: Hypnotic in short-term treatment of insomnia; to reduce anxiety and
provide sedation preoperatively
I.M., I.V.: Control status epilepticus or acute seizure episodes. Also used
to control acute episodes of agitated behavior in psychosis and in
"Amytal® Interviewing" for narcoanalysis
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Restrictions |
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C-II |
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Pregnancy Risk
Factor |
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D |
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Contraindications |
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Hypersensitivity to barbiturates or any component of the formulation; marked
hepatic impairment; dyspnea or airway obstruction;
porphyria |
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Warnings/Precautions |
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Safety has not been established in children <6 years of age. Use with
caution in patients with CHF, hepatic or renal impairment, hypovolemic shock;
when administered I.V., respiratory depression and hypotension are possible,
have equipment and personnel available; this I.V. medication should be given
only to hospitalized patients. Do not administer to patients in acute pain. Use
caution in elderly, debilitated, renally impaired, hepatic impairment, 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 (ie, operating machinery or driving). Effects with
other sedative drugs or ethanol may be potentiated. Use with caution in patients
with hypoadrenalism. |
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Adverse
Reactions |
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>10%:
Central nervous system: Dizziness, lightheadedness, "hangover" effect,
drowsiness, CNS depression, fever
Local: Pain at injection site
1% to 10%:
Central nervous system: Confusion, mental depression, unusual excitement,
nervousness, faint feeling, headache, insomnia, nightmares
Gastrointestinal: Nausea, vomiting, constipation
<1%: Hypotension, hallucinations, rash, exfoliative dermatitis, urticaria,
Stevens-Johnson syndrome, agranulocytosis, megaloblastic anemia,
thrombocytopenia, thrombophlebitis, respiratory depression, apnea, laryngospasm
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Overdosage/Toxicology |
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Symptoms of overdose include unsteady gait, slurred speech, confusion,
jaundice, hypothermia, fever, hypotension
If hypotension occurs, administer I.V. fluids and place the patient in the
Trendelenburg position. If unresponsive, an I.V. vasopressor (eg, dopamine,
epinephrine) may be required. Forced alkaline diuresis is of no value in the
treatment of intoxications with short-acting barbiturates. Charcoal
hemoperfusion or hemodialysis may be useful in the harder to treat
intoxications, especially in the presence of very high serum barbiturate levels.
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Drug
Interactions |
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Barbiturates are enzyme inducers. Patients should be monitored when these
drugs are started or stopped for a decreased or increased therapeutic effect
respectively.
Barbiturates may enhance the hepatotoxic potential of overdoses of
acetaminophen
Acetazolamide may decrease absorption of primidone (metabolized to
phenobarbital) and reduce clinical effects
Barbiturates may increase the metabolism of some beta-blockers and decrease
their clinical effect (atenolol and nadolol unlikely to interact given their
renal elimination)
Barbiturates may increase the metabolism of chloramphenicol and
chloramphenicol may inhibit barbiturate metabolism; monitor for altered response
Barbiturates may enhance the metabolism (decrease the efficacy) of
antipsychotics; monitor for altered response; dose adjustment may be needed
Barbiturates may enhance the metabolism of calcium channel blockers,
cimetidine, corticosteroids, cyclosporine, disopyramide, doxycycline,
ethosuximide, furosemide, griseofulvin, lamotrigine, phenytoin, propafenone,
quinidine, tacrolimus, TCAs, theophylline; dose adjustment may be needed
Barbiturates may increase the metabolism of estrogens and reduce the efficacy
of oral contraceptives; an alternative method of contraception should be
considered
Barbiturates, ethanol, and narcotic analgesics have additive CNS depressant
effects
Felbamate may inhibit the metabolism of barbiturates and barbiturates may
increase the metabolism of felbamate
Barbiturates may impair the absorption of griseofulvin
MAOIs may inhibit the metabolism of barbiturates
Barbiturates may enhance the nephrotoxic effects of methoxyflurane
Valproic acid inhibits the metabolism of barbiturates; monitor for excessive
sedation; a dose reduction may be needed
Barbiturates inhibit the hypoprothrombinemic effects of oral anticoagulants
via increased metabolism; this combination should generally be avoided
Barbiturates may enhance the metabolism of methadone resulting in methadone
withdrawal |
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Stability |
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Hydrolyzes when exposed to air; use contents of vial within 30 minutes after
constitution; use only clear solution |
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Mechanism of
Action |
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Interferes with transmission of impulses from the thalamus to the cortex of
the brain resulting in an imbalance in central inhibitory and facilitatory
mechanisms |
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Pharmacodynamics/Kinetics |
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Onset of action: Oral: Within 1 hour; I.V.: Within 5 minutes
Distribution: Readily crosses the placenta; small amounts appear in breast
milk
Metabolism: Chiefly in the liver by microsomal enzymes
Half-life, biphasic: Initial: 40 minutes; Terminal: 20 hours
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Usual Dosage |
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Children: Oral:
Sedation: 6 mg/kg/day divided every 6-8 hours
Insomnia: 2 mg/kg or 70 mg/m2/day in 4 equally divided doses
Hypnotic: 2-3 mg/kg
Adults:
Insomnia: Oral: 65-200 mg at bedtime
Sedation: Oral: 30-50 mg 2-3 times/day
Preanesthetic: Oral: 200 mg 1-2 hours before surgery
Hypnotic:
Oral: 65-200 mg at bedtime
I.M., I.V.: 65-500 mg, should not exceed 500 mg I.M. or 1000 mg I.V.
Amobarbital interview: I.V.: 50 mg/minute for total dose up to 300 mg
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Dietary
Considerations |
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Alcohol: Avoid use |
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Monitoring
Parameters |
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Vital signs should be monitored during injection and for several hours after
administration |
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Reference Range |
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Therapeutic: 1-5 mg/mL (SI: 4-22
mmol/L)
Toxic: >10 mg/mL (SI: >44
mmol/L)
Lethal: >50 mg/mL |
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Test
Interactions |
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ammonia (B);
bilirubin
(S) |
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Dental Health: Local
Anesthetic/Vasoconstrictor
Precautions |
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No information available to require special precautions |
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Dental Health:
Effects on Dental Treatment |
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No effects or complications reported |
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Patient
Information |
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I.V./I.M.: Patient instructions and information are determined by patient
condition and therapeutic purpose. If self-administered, use exactly as directed
(do not increase dose or frequency or discontinue without consulting
prescriber); may cause physical and/or psychological dependence. While using
this medication, do not use alcohol or other prescription or OTC medications
(especially pain medications, sedatives, antihistamines, or hypnotics) without
consulting prescriber. Maintain adequate hydration (2-3 L/day of fluids unless
instructed to restrict fluid intake). You may experience drowsiness, dizziness,
or blurred vision (use caution when driving or engaging in tasks requiring
alertness until response to drug is known); nausea, vomiting, or loss of
appetite (small frequent meals, frequent mouth care, chewing gum, or sucking
lozenges may help); constipation (increased exercise, fluids, or dietary fruit
and fiber may help). If medication is used to control seizures, wear
identification of epileptic status and medication. Report skin rash or
irritation; CNS changes (confusion, depression, increased sedation, excitation,
headache, insomnia, or nightmares); difficulty breathing or shortness of breath;
changes in urinary pattern or menstrual pattern; muscle weakness or tremors; or
difficulty swallowing or feeling of tightness in throat.
Pregnancy/breast-feeding precautions: Do not get pregnant while taking this
medication; use appropriate barrier contraceptive measures. Breast-feeding is
not recommended. |
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Nursing
Implications |
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Raise bed rails at night |
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Dosage Forms |
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Capsule, as sodium: 65 mg, 200 mg
Injection, as sodium: 500 mg
Tablet: 30 mg, 50 mg, 100 mg |
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