Source: FDA, National Drug Code (US) Revision Year: 2020
The dose of amobarbital sodium must be individualized with full knowledge of its particular characteristics and recommended rate of administration. Factors of consideration are the patient’s age, weight, and condition. The maximum single dose for an adult is 1 g.
Intramuscular injection of the sodium salts of barbiturates should be made deeply into a large muscle. The average IM dose ranges from 65 mg to 0.5 g. A 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. After IM injection of a hypnotic dose, the patient’s vital signs should be monitored. Superficial IM or subcutaneous injections may be painful and may produce sterile abscesses or sloughs.
Intravenous (IV) injection is restricted to conditions in which other routes are not feasible, either because the patient is unconscious (as in cerebral hemorrhage, eclampsia, or status epilepticus), because the patient resists (as in delirium), or because prompt action is imperative. Slow IV injection is essential, and patients should be carefully observed during administration. This requires that blood pressure, respiration, and cardiac function 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. The final dosage is determined to a great extent by the patient’s reaction to the slow administration of the drug.
Sedative: 30 to 50 mg given 2 or 3 times daily.
Hypnotic: 65 to 200 mg at bedtime.
Dosage should be reduced in the elderly or debilitated because these patients may be more sensitive to barbiturates. Dosage should be reduced for patients with impaired renal function or hepatic disease. Ordinarily, an IV dose of 65 mg to 0.5 g may be given to a child 6 to 12 years of age.
The toxic dose of barbiturates varies considerably. In general, an oral dose of 1 g of most barbiturates produces serious poisoning in an adult. Toxic effects and fatalities have occurred following overdoses of amobarbital sodium alone and in combination with other CNS depressants. Death commonly occurs after 2 to 10 g of ingested barbiturate. The sedated, therapeutic blood levels of amobarbital range between 2 to 10 mcg/mL; the usual lethal blood level ranges from 40 to 80 mcg/mL. Barbiturate intoxication may be confused with alcoholism, bromide intoxication, and various neurologic disorders. Potential tolerance must be considered when evaluating significance of dose and plasma concentration.
Symptoms of oral overdose may occur within 15 minutes beginning with CNS depression, absent or sluggish reflexes, underventilation, hypotension, and hypothermia and may progress to pulmonary edema and death. Hemorrhagic blisters may develop, especially at pressure points.
In extreme overdose, all electrical activity in the brain may cease, in which case a “flat” EEG normally equated with clinical death cannot be accepted. This effect is fully reversible unless hypoxic damage occurs. Consideration should be given to the possibility of barbiturate intoxication even in situations that appear to involve trauma.
Complications such as pneumonia, pulmonary edema, cardiac arrhythmias, congestive heart failure, and renal failure may occur. Uremia may increase CNS sensitivity to barbiturates if renal function is impaired. Differential diagnosis should include hypoglycemia, head trauma, cerebrovascular accidents, convulsive states, and diabetic coma.
To obtain up-to-date information about the treatment of overdose, a good resource is your certified Regional Poison Control Center. Telephone numbers of certified poison control centers are listed in the Physicians' Desk Reference (PDR)*. In managing overdosage, consider the possibility of multiple drug overdoses, interaction among drugs, and unusual drug kinetics in your patient.
Protect the patient’s airway and support ventilation and perfusion. Meticulously monitor and maintain, within acceptable limits, the patient’s vital signs, blood gases, serum electrolytes, etc. Absorption of drugs from the gastrointestinal tract may be decreased by giving activated charcoal, which, in many cases, is more effective than emesis or lavage; consider charcoal instead of or in addition to gastric emptying. Repeated doses of charcoal over time may hasten elimination of some drugs that have been absorbed. Safeguard the patient’s airway when employing gastric emptying or charcoal.
Diuresis and peritoneal dialysis are of little value; hemodialysis and hemoperfusion enhance drug clearance and should be considered in serious poisoning. If the patient has chronically abused sedatives, withdrawal reactions may be manifest following acute overdose.
Store at (15° to 30°C) (59° to 86°F)
Lyophilized
Solutions of amobarbital sodium should be made up aseptically with Sterile Water for Injection. The accompanying table will aid in preparing solutions of various concentrations. Ordinarily, a 10% solution is used. After Sterile Water for Injection is added, the vial should be rotated to facilitate solution of the powder. Do not shake the vial.
Several minutes may be required for the drug to dissolve completely, but under no circumstances should a solution be injected if it has not become absolutely clear within 5 minutes. Also, a solution that forms a precipitate after clearing should not be used. Amobarbital sodium hydrolyzes in solution or on exposure to air. Not more than 30 minutes should elapse from the time the vial is opened until its contents are injected. Prior to administration, parenteral drug products should be inspected visually for particulate matter and discoloration whenever solution containers permit.
Quantity of Sterile Water for Injection Required to Dilute the Contents of a Given Vial of Amobarbital Sodium to Obtain the Percentages Listed. Solutions Derived Will Be in Weight/Volume:
| AMOBARBITAL SODIUM | |||||
|---|---|---|---|---|---|
| Content in Weight | 1% | 2.5% | 5% | 10% | 20% |
| 0.5 g | 50 mL | 20 mL | 10 mL | 5 mL | 2.5 mL |
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