secobarbital sodium
Seconal

Available forms
Available by prescription only
Capsules: 100 mg

Indications and dosages
 Preoperative sedation. Adults: 200 to 300 mg P.O. 1 to 2 hours before surgery.
Children: 2 to 6 mg/kg P.O. (maximum dose, 100 mg).
 Insomnia. Adults: 100 mg P.O.

Pharmacodynamics
Sedative-hypnotic action: Secobarbital acts throughout the CNS as a nonselective depressant with a rapid onset and short duration of action. Particularly sensitive to this drug is the reticular activating system, which controls CNS arousal. Secobarbital decreases both presynaptic and postsynaptic membrane excitability by facilitating the action of gamma-aminobutyric acid. The exact cellular site and mechanisms of action are unknown.

Pharmacokinetics
Absorption: 90% is absorbed rapidly. Levels of 1 to 5 mcg/ml are needed to produce sedation; 5 to 15 mcg/ml are needed for hypnosis.
Distribution: Distributed rapidly throughout body tissues and fluids; about 30% to 45% is protein-bound.
Metabolism: Oxidized in the liver to inactive metabolites. Duration of action is 3 to 4 hours.
Excretion: About 95% of a dose is eliminated as glucuronide conjugates and other metabolites in urine. Drug has an elimination half-life of about 30 hours.

Contraindications and precautions
Contraindicated in patients with respiratory disease involving dyspnea or obstruction and in patients hypersensitive to barbiturates or porphyria.
  Use cautiously in patients with acute or chronic pain, depression, suicidal tendencies, history of drug abuse, or impaired hepatic or renal function.

Interactions
Drug-drug. Antidepressants, antihistamines, narcotics, sedative-hypnotics, tranquilizers: Secobarbital may add to or potentiate CNS and respiratory depressant effects. Use together cautiously.
Corticosteroids, digitoxin (not digoxin), doxycycline, hormonal contraceptives and other estrogens, theophylline and other xanthines, warfarin and other oral anticoagulants: Enhances metabolism of these drugs. Monitor patient for lack of effect.
Disulfiram, MAO inhibitors, valproic acid: Decreases metabolism of secobarbital and increases risk of toxicity. Reduce barbiturate dosage.
Griseofulvin: Impairs griseofulvin effectiveness by decreasing absorption from the GI tract. Monitor effectiveness of griseofulvin.
Rifampin: May decrease secobarbital levels by increasing metabolism. Monitor patient for decreased effect.
Drug-lifestyle. Alcohol use: May potentiate CNS depressant effects. Discourage alcohol use.

Adverse reactions
CNS: drowsiness, lethargy, hangover, paradoxical excitement in elderly patients, somnolence, altered EEG patterns.
GI: nausea, vomiting.
Hematologic: worsening of porphyria.
Respiratory: respiratory depression.
Skin: rash, urticaria, Stevens-Johnson syndrome, tissue reactions, injection-site pain.
Other: angioedema, physical and psychological dependence.

Effects on lab test results
• May decrease bilirubin levels.

Overdose and treatment
Signs and symptoms of overdose include unsteady gait, slurred speech, sustained nystagmus, somnolence, confusion, respiratory depression, pulmonary edema, areflexia, and coma. Typical shock syndrome with tachycardia and hypotension, jaundice, hypothermia followed by fever, and oliguria may occur.
 Maintain and support ventilation and pulmonary function as needed; support cardiac function and circulation with vasopressors and I.V. fluids as needed. If patient is conscious and gag reflex is intact, induce emesis (if ingestion was recent) by administering ipecac syrup. If emesis is contraindicated, perform gastric lavage while a cuffed endotracheal tube is in place to prevent aspiration. Follow with administration of activated charcoal or sodium chloride cathartic. Measure intake and output, vital signs, and laboratory parameters; maintain body temperature. Roll patient from side to side every 30 minutes to avoid pulmonary congestion. Alkalinization of urine may help remove drug from the body; hemodialysis may be useful in severe overdose.

Special considerations
• Assess mental status before starting therapy.
• Take precautions to prevent hoarding or overdosing by patients who are depressed, suicidal, or drug-dependent or who have history of drug abuse.
• Monitor hepatic and renal studies frequently to prevent possible toxicity.
• Inspect patient’s skin. Skin eruptions may precede potentially fatal reactions to barbiturate therapy. Discontinue drug when skin reactions occur. In some patients, high fever, stomatitis, headache, or rhinitis may precede skin reactions.
• Long-term use isn’t recommended; drug loses its efficacy in promoting sleep after 14 days of continued use.
• Secobarbital may cause a false-positive phentolamine test. The physiologic effects of the drug may impair absorption of cyanocobalamin C57.
• Watch for signs of barbiturate toxicity: coma, pupillary constriction, cyanosis, clammy skin, and hypotension. Overdose can be fatal.
Breast-feeding patients
• Drug appears in breast milk. Don’t administer to breast-feeding women.
Pediatric patients
• Drug may cause paradoxical excitement in children; use cautiously.
Geriatric patients
• These patients are more susceptible to effects of drug and usually need lower doses. Confusion, disorientation, and excitability may occur.

Patient education
• Inform patient that morning hangover is common after hypnotic dose, which suppresses rapid eye movement (REM) sleep.
• Caution patient not to perform activities that require mental alertness or physical coordination.

Reactions may be common, uncommon, life-threatening, or COMMON AND LIFE THREATENING.
◆ Canada only
◇ Unlabeled clinical use