Drug information of Amobarbital

Amobarbital

Drug group: Anticonvulsants

Amobarbital  is a barbiturate with hypnotic and sedative properties (but not antianxiety).

Mechanism of effect

Amobarbital (like all barbiturates) works by binding to the GABAA receptor at either the alpha or the beta sub unit. These are binding sites that are distinct from GABA itself and also distinct from the benzodiazepine binding site.

 Like benzodiazepines, barbiturates potentiate the effect of GABA at this receptor. Amobarbital depresses the sensory cortex by interfering with transmission of impulses from thalamus. This results in decreased motor activity, altered cerebellar function, drowsiness, sedation, and hypnosis

Pharmacodynamic

Acts throughout the CNS as a nonselective depressant with an intermediate onset and duration of action. Particularly sensitive to this drug is the mesencephalic reticular activating system, which controls CNS arousal. Drug decreases both presynaptic and postsynaptic membrane excitability by facilitating the action of GABA. 

Pharmacokinetics

Absorption:

Onset of Action: Within 5 minutes

Distribution:

NOT AVAILABLE

Metabolism:
Primarily hepatic via microsomal enzymes

Elimination:
Half-Life: 15-40 hours in adults (mean 25 hours)

Excretion: feces, urine

Drug indications

Anxiety , Insomnia

Dosage

  • 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.
  • 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

Alerts

  • 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.
  • 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

Points of recommendation

  • Patient should avoid activities requiring mental alertness or coordination until drug effects are realized, as drug may cause dizziness, confusion, or somnolence.
  • This drug may cause headache or apnea.
  • Patient should avoid alcohol or other CNS depressants while taking this drug, as this may cause additive CNS depression.

Pregnancy level

D


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