Wada test (off-label use):
Note: Due to the adverse effects associated with intra-carotid amobarbital and questionable reliability and validity, other less invasive tests (eg, functional MRI) may be recommended (Sharan 2011).
Intra-carotid: 60 to 200 mg (usual dose: 125 mg) over 2 to 5 seconds via percutaneous transfemoral catheter; after 30 to 45 minutes has elapsed since completion of first injection, may repeat dose for evaluation of contralateral hemisphere (Acharya 1997; Patel 2011).
Dosage adjustment for concomitant therapy: Significant drug interactions exist, requiring dose/frequency adjustment or avoidance. Consult drug interactions database for more information.
There are no dosage adjustments provided in the manufacturer's labeling; reduced doses are recommended.
There are no dosage adjustments provided in the manufacturer's labeling; reduced doses are recommended. Do not administer to patients with hepatic encephalopathy.
(For additional information see "Amobarbital: Pediatric drug information")
Note: Dosage should be individualized with consideration of patient's age, weight, and medical condition. Although described in the manufacturer labeling, amobarbital is not recommended for use in the management of pediatric insomnia, procedural sedation, or other types of nonprocedural sedation (eg, sedation in mechanically ventilated patients) (Barnes 2016; Brown 2016; Curley 2015; Krauss 2006).
Sedation, preoperative or procedural:
Children ≥6 years and Adolescents: IM (preferred), IV: Usual recommendation: 2 to 3 mg/kg/dose; maximum dose: 500 mg/dose; dosing based on generally recognized expert recommendations; published pediatric trial data is lacking (Nelson 1996). The manufacturer describes the ordinary dose range in children 6 to 12 years as 65 to 500 mg and specific dosing recommendations based on patient size are not available; however, in several instances, this may exceed expert weight-based recommendations; if using manufacturer dosing, initiate therapy at the lower end of the range and titrate the dose accordingly.
Intracarotid amobarbital procedure (Wada test): Limited data available; dosing regimens variable: Children ≥6 years and Adolescents: Intra-arterial: 75 to 125 mg/dose; typically administered through femoral arterial catheter; consult institution-specific protocols (Acharya 1997; Burns 2009; Hinz 1994; Kim 2007; Szabó 1993).
Dosage adjustment for concomitant therapy: Significant drug interactions exist, requiring dose/frequency adjustment or avoidance. Consult drug interactions database for more information.
There are no dosage adjustments provided in the manufacturer's labeling; dosing should be reduced; specific recommendations not available.
There are no dosage adjustments provided in the manufacturer's labeling; dosing should be reduced; specific recommendations not available; drug is contraindicated in patients with marked hepatic impairment; avoid use in patients with premonitory signs of hepatic coma.
Avoid use (Beers Criteria [AGS 2019]).
Excipient information presented when available (limited, particularly for generics); consult specific product labeling.
Solution Reconstituted, Injection, as sodium:
Amytal Sodium: 500 mg (1 ea)
No
C-II
IM: Administer deeply into a large muscle. Do not use more than 5 mL (irrespective of concentration) at any single site (may cause tissue damage). Use 20% solution to facilitate larger doses. Superficial IM or subcutaneous injections may be painful and produce sterile abscesses or sloughs.
IV: Use only when IM administration is not feasible. Administer by slow IV injection (maximum rate of infusion: 50 mg/minute in adults).
Intra-carotid (off-label route): Wada test (off-label use): Administer dose over 2 to 5 seconds via percutaneous transfemoral catheter into the internal carotid artery (Acharya 1997).
Parenteral: Following reconstitution, dose must be administered within 30 minutes.
IM (preferred): Administer deeply into a large muscle. Do not use more than 5 mL at any single site (may cause tissue damage).
IV: Use only when IM administration is not feasible. Administer by slow IV injection (maximum rate: 50 mg/minute in adults).
Intracarotid: Wada test: Administer dose over 2 to 5 seconds via percutaneous transfemoral catheter into the internal carotid artery (Acharya 1997).
Although described in the manufacturer's labeling, amobarbital is not recommended for use in the management of insomnia, procedural sedation, or other types of nonprocedural sedation (eg, sedation in mechanically ventilated patients) (AASM [Sateia 2017]; SCCM [Devlin 2018]).
Wada test
Beers Criteria: Amobarbital is identified in the Beers Criteria as a potentially inappropriate medication to be avoided in patients 65 years and older (independent of diagnosis or condition) due to its high rate of physical dependence, tolerance to sleep benefits, and increased risk of overdose at low dosages (Beers Criteria [AGS 2019]).
Pharmacy Quality Alliance (PQA): Amobarbital is identified as a high-risk medication in patients 65 years and older on the PQA’s, Use of High-Risk Medications in the Elderly (HRM) performance measure, a safety measure used by the Centers for Medicare and Medicaid Services (CMS) for Medicare plans (PQA 2017).
The following adverse drug reactions and incidences are derived from product labeling unless otherwise specified. Frequency not defined and is reported as barbiturate use (not specifically amobarbital).
Cardiovascular: Bradycardia, hypotension, syncope
Central nervous system: Abnormality in thinking, agitation, anxiety, ataxia, central nervous system depression, confusion, dizziness, drowsiness, hallucination, headache, insomnia, nervousness, nightmares, psychiatric disturbance
Gastrointestinal: Constipation, nausea, vomiting
Hematologic & oncologic: Megaloblastic anemia (following chronic phenobarbital use)
Hepatic: Hepatic injury
Hypersensitivity: Hypersensitivity reaction (including angioedema, skin rash, and exfoliative dermatitis)
Local: Injection site reaction
Neuromuscular & skeletal: Hyperkinesia
Respiratory: Apnea, atelectasis (postoperative), hypoventilation
Miscellaneous: Fever
Hypersensitivity to barbiturates or any component of the formulation; history of manifest or latent porphyria; marked liver function impairment; marked respiratory disease in which dyspnea or obstruction is evident.
Concerns related to adverse effects:
• CNS depression: 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).
• Paradoxical responses: May cause paradoxical excitement, particularly in patients with acute or chronic pain.
Disease-related concerns:
• Adrenal insufficiency: Use with caution in patients with adrenal insufficiency. Systemic effects of exogenous and endogenous corticosteroids may be diminished by amobarbital.
• Depression: Use with caution, if at all, in patients with depression or suicidal tendencies.
• Drug abuse: Use with caution, if at all, in patients with a history of substance or alcohol use disorder; potential for drug dependency exists. Tolerance and psychological and physical dependence may occur with prolonged use.
• Hepatic impairment: Use with caution in patients with hepatic impairment, decreased dosage may be needed. Do not administer to patients with hepatic encephalopathy.
• Renal impairment: Use with caution in patients with renal impairment; decreased dosage may be needed.
• Respiratory disease: Use with caution in patients with respiratory disease; may cause respiratory depression.
Special populations:
• Older adults: Avoid use in older adults; may react to barbiturates with marked excitement, depression, and confusion (Beers Criteria [AGS 2019]; manufacturer's labeling).
• Pediatric: Barbiturates repeatedly produce excitement rather than depression in some patients, particularly children. Neonates may experience withdrawal symptoms with chronic maternal use; monitor closely. In pediatric patients, barbiturates may produce paradoxical excitement.
Dosage form specific issues:
• Alkaline solution: Solution for injection is highly alkaline and extravasation may cause local tissue damage with subsequent necrosis.
Other warnings/precautions:
• Administration: Rapid IV administration may cause respiratory depression, apnea, laryngospasm, or vasodilation with a fall in blood pressure; avoid perivascular extravasation or intra-arterial injection; discontinue if patient complains of pain in the limb. Restrict use of IV administration to conditions in which other routes are not feasible, if patient is unconscious (eg, cerebral hemorrhage, eclampsia, or status epilepticus) or patient resists (eg, delirium), or because prompt action is imperative.
• Withdrawal: Abrupt cessation may precipitate withdrawal, including delirium and convulsions (some fatal); withdraw gradually.
None known.
Note: Interacting drugs may not be individually listed below if they are part of a group interaction (eg, individual drugs within “CYP3A4 Inducers [Strong]” are NOT listed). For a complete list of drug interactions by individual drug name and detailed management recommendations, use the Lexicomp drug interactions program by clicking on the “Launch drug interactions program” link above.
Alcohol (Ethyl): CNS Depressants may enhance the CNS depressant effect of Alcohol (Ethyl). Risk C: Monitor therapy
Alizapride: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Azelastine (Nasal): May enhance the CNS depressant effect of CNS Depressants. Risk X: Avoid combination
Blonanserin: CNS Depressants may enhance the CNS depressant effect of Blonanserin. Management: Use caution if coadministering blonanserin and CNS depressants; dose reduction of the other CNS depressant may be required. Strong CNS depressants should not be coadministered with blonanserin. Risk D: Consider therapy modification
Blood Pressure Lowering Agents: Barbiturates may enhance the hypotensive effect of Blood Pressure Lowering Agents. Risk C: Monitor therapy
Brexanolone: CNS Depressants may enhance the CNS depressant effect of Brexanolone. Risk C: Monitor therapy
Brimonidine (Topical): May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Bromopride: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Bromperidol: May enhance the CNS depressant effect of CNS Depressants. Risk X: Avoid combination
Buprenorphine: CNS Depressants may enhance the CNS depressant effect of Buprenorphine. Management: Consider reduced doses of other CNS depressants, and avoiding such drugs in patients at high risk of buprenorphine overuse/self-injection. Initiate buprenorphine at lower doses in patients already receiving CNS depressants. Risk D: Consider therapy modification
Cannabinoid-Containing Products: CNS Depressants may enhance the CNS depressant effect of Cannabinoid-Containing Products. Risk C: Monitor therapy
Chlormethiazole: May enhance the CNS depressant effect of CNS Depressants. Management: Monitor closely for evidence of excessive CNS depression. The chlormethiazole labeling states that an appropriately reduced dose should be used if such a combination must be used. Risk D: Consider therapy modification
Chlorphenesin Carbamate: May enhance the adverse/toxic effect of CNS Depressants. Risk C: Monitor therapy
CNS Depressants: May enhance the adverse/toxic effect of other CNS Depressants. Risk C: Monitor therapy
Daridorexant: May enhance the CNS depressant effect of CNS Depressants. Management: Dose reduction of daridorexant and/or any other CNS depressant may be necessary. Use of daridorexant with alcohol is not recommended, and the use of daridorexant with any other drug to treat insomnia is not recommended. Risk D: Consider therapy modification
DexmedeTOMIDine: CNS Depressants may enhance the CNS depressant effect of DexmedeTOMIDine. Management: Monitor for increased CNS depression during coadministration of dexmedetomidine and CNS depressants, and consider dose reductions of either agent to avoid excessive CNS depression. Risk D: Consider therapy modification
Difelikefalin: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Dimethindene (Topical): May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Doxycycline: Barbiturates may decrease the serum concentration of Doxycycline. Risk C: Monitor therapy
Doxylamine: May enhance the CNS depressant effect of CNS Depressants. Management: The manufacturer of Diclegis (doxylamine/pyridoxine), intended for use in pregnancy, specifically states that use with other CNS depressants is not recommended. Risk C: Monitor therapy
Droperidol: May enhance the CNS depressant effect of CNS Depressants. Management: Consider dose reductions of droperidol or of other CNS agents (eg, opioids, barbiturates) with concomitant use. Risk D: Consider therapy modification
Esketamine: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Flunarizine: CNS Depressants may enhance the CNS depressant effect of Flunarizine. Risk X: Avoid combination
Flunitrazepam: CNS Depressants may enhance the CNS depressant effect of Flunitrazepam. Management: Reduce the dose of CNS depressants when combined with flunitrazepam and monitor patients for evidence of CNS depression (eg, sedation, respiratory depression). Use non-CNS depressant alternatives when available. Risk D: Consider therapy modification
Griseofulvin: Barbiturates may decrease the serum concentration of Griseofulvin. Risk C: Monitor therapy
Hemin: Barbiturates may diminish the therapeutic effect of Hemin. Risk X: Avoid combination
HydrOXYzine: May enhance the CNS depressant effect of CNS Depressants. Management: Consider a decrease in the CNS depressant dose, as appropriate, when used together with hydroxyzine. Increase monitoring of signs/symptoms of CNS depression in any patient receiving hydroxyzine together with another CNS depressant. Risk D: Consider therapy modification
Kava Kava: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Kratom: May enhance the CNS depressant effect of CNS Depressants. Risk X: Avoid combination
Lemborexant: May enhance the CNS depressant effect of CNS Depressants. Management: Dosage adjustments of lemborexant and of concomitant CNS depressants may be necessary when administered together because of potentially additive CNS depressant effects. Close monitoring for CNS depressant effects is necessary. Risk D: Consider therapy modification
Lisuride: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Lofexidine: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Magnesium Sulfate: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Methotrimeprazine: CNS Depressants may enhance the CNS depressant effect of Methotrimeprazine. Methotrimeprazine may enhance the CNS depressant effect of CNS Depressants. Management: Reduce the usual dose of CNS depressants by 50% if starting methotrimeprazine until the dose of methotrimeprazine is stable. Monitor patient closely for evidence of CNS depression. Risk D: Consider therapy modification
Methoxyflurane: Barbiturates may enhance the nephrotoxic effect of Methoxyflurane. Barbiturates may increase the metabolism of Methoxyflurane. Risk X: Avoid combination
Metoclopramide: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
MetyroSINE: CNS Depressants may enhance the sedative effect of MetyroSINE. Risk C: Monitor therapy
Mianserin: May enhance the CNS depressant effect of Barbiturates. Mianserin may diminish the therapeutic effect of Barbiturates. Barbiturates may decrease the serum concentration of Mianserin. Risk X: Avoid combination
Minocycline (Systemic): May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Multivitamins/Minerals (with ADEK, Folate, Iron): May decrease the serum concentration of Barbiturates. Risk C: Monitor therapy
Olopatadine (Nasal): May enhance the CNS depressant effect of CNS Depressants. Risk X: Avoid combination
Opioid Agonists: CNS Depressants may enhance the CNS depressant effect of Opioid Agonists. Management: Avoid concomitant use of opioid agonists and benzodiazepines or other CNS depressants when possible. These agents should only be combined if alternative treatment options are inadequate. If combined, limit the dosages and duration of each drug. Risk D: Consider therapy modification
Orphenadrine: CNS Depressants may enhance the CNS depressant effect of Orphenadrine. Risk X: Avoid combination
Oxomemazine: May enhance the CNS depressant effect of CNS Depressants. Risk X: Avoid combination
Oxybate Salt Products: CNS Depressants may enhance the CNS depressant effect of Oxybate Salt Products. Management: Consider alternatives to this combination when possible. If combined, dose reduction or discontinuation of one or more CNS depressants (including the oxybate salt product) should be considered. Interrupt oxybate salt treatment during short-term opioid use Risk D: Consider therapy modification
OxyCODONE: CNS Depressants may enhance the CNS depressant effect of OxyCODONE. Management: Avoid concomitant use of oxycodone and benzodiazepines or other CNS depressants when possible. These agents should only be combined if alternative treatment options are inadequate. If combined, limit the dosages and duration of each drug. Risk D: Consider therapy modification
Paraldehyde: CNS Depressants may enhance the CNS depressant effect of Paraldehyde. Risk X: Avoid combination
Perampanel: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Piribedil: CNS Depressants may enhance the CNS depressant effect of Piribedil. Risk C: Monitor therapy
Pramipexole: CNS Depressants may enhance the sedative effect of Pramipexole. Risk C: Monitor therapy
Procarbazine: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Ropeginterferon Alfa-2b: CNS Depressants may enhance the adverse/toxic effect of Ropeginterferon Alfa-2b. Specifically, the risk of neuropsychiatric adverse effects may be increased. Management: Avoid coadministration of ropeginterferon alfa-2b and other CNS depressants. If this combination cannot be avoided, monitor patients for neuropsychiatric adverse effects (eg, depression, suicidal ideation, aggression, mania). Risk D: Consider therapy modification
ROPINIRole: CNS Depressants may enhance the sedative effect of ROPINIRole. Risk C: Monitor therapy
Rotigotine: CNS Depressants may enhance the sedative effect of Rotigotine. Risk C: Monitor therapy
Rufinamide: May enhance the adverse/toxic effect of CNS Depressants. Specifically, sleepiness and dizziness may be enhanced. Risk C: Monitor therapy
Suvorexant: CNS Depressants may enhance the CNS depressant effect of Suvorexant. Management: Dose reduction of suvorexant and/or any other CNS depressant may be necessary. Use of suvorexant with alcohol is not recommended, and the use of suvorexant with any other drug to treat insomnia is not recommended. Risk D: Consider therapy modification
Thalidomide: CNS Depressants may enhance the CNS depressant effect of Thalidomide. Risk X: Avoid combination
Theophylline Derivatives: Barbiturates may decrease the serum concentration of Theophylline Derivatives. Risk C: Monitor therapy
Tricyclic Antidepressants: Barbiturates may increase the metabolism of Tricyclic Antidepressants. Management: Monitor for decreased efficacy of tricyclic antidepressants if a barbiturate is initiated/dose increased, or increased effects if a barbiturate is discontinued/dose decreased. Tricyclic antidepressant dose adjustments are likely required. Risk D: Consider therapy modification
Trimeprazine: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Valerian: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Valproate Products: May increase the serum concentration of Barbiturates. Barbiturates may decrease the serum concentration of Valproate Products. Risk C: Monitor therapy
Vitamin K Antagonists (eg, warfarin): Barbiturates may increase the metabolism of Vitamin K Antagonists. Management: Monitor INR more closely. Anticoagulant dose increases of 30% to 60% may be needed after a barbiturate is initiated or given at an increased dose. Anticoagulant dose decreases may be needed following barbiturate discontinuation or dose reduction. Risk D: Consider therapy modification
Zolpidem: CNS Depressants may enhance the CNS depressant effect of Zolpidem. Management: Reduce the Intermezzo brand sublingual zolpidem adult dose to 1.75 mg for men who are also receiving other CNS depressants. No such dose change is recommended for women. Avoid use with other CNS depressants at bedtime; avoid use with alcohol. Risk D: Consider therapy modification
Barbiturates cross the placenta and distribute in fetal tissue. Teratogenic effects have been reported with first trimester exposure. Exposure during the third trimester may lead to symptoms of acute withdrawal following delivery; symptoms may be delayed up to 14 days.
Small amounts of barbiturates are present in breast milk; information specific for amobarbital is not available. The manufacturer recommends that caution be used if administered to a patient who is breastfeeding.
Vital signs and cardiac function (during IV administration); renal and hepatic function with prolonged therapy.
Therapeutic: 1-5 mcg/mL (SI: 4-22 micromole/L)
Toxic: >10 mcg/mL (SI: >44 micromole/L)
Lethal: >50 mcg/mL
An intermediate-acting barbiturate; barbiturates depress the sensory cortex, decrease motor activity, and alter cerebellar function producing drowsiness, sedation, and hypnosis.
Onset of action: Rapid, within minutes
Duration of action: Variable
Metabolism: Primarily hepatic via microsomal enzymes
Half-life elimination: 16 to 40 hours (mean: 25 hours)
Time to peak: Maximum effect: Hours
Excretion: Urine (as metabolites, negligible amounts excreted unchanged in urine); feces (metabolites)
Solution (reconstituted) (Amytal Sodium Injection)
500 mg (per each): $879.66
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