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What is Phenobarbital?

  • Phenobarbital (Luminal) is a long-acting barbiturate, is a central nervous system depressant used as a sedative or anticonvulsant.
Phenobarbital ball-and-stick

What are the uses of this medicine?

Phenobarbital is used as:

How does this medicine work?

  • Phenobarbital (fee" noe bar' bi tal) is a barbiturate and is believed to act as a nonselective depressant.
  • Phenobarbital also has anticonvulsant activity and is believed to act by suppressing spread of seizure activity by enhancing the effect of gamma aminobutyric acid (GABA), raising the seizure threshold.

Who Should Not Use this medicine ?

This medicine cannot be used in patients:

What drug interactions can this medicine cause?

  • Tell your doctor and pharmacist what other prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking or plan to take.

Be sure to mention the following:

Is this medicine FDA approved?

  • Phenobarbital was introduced into clinical medicine in 1911 but was never subjected to critical controlled studies to demonstrate safety and efficacy.
  • For these reasons, phenobarbital is now considered of unproven benefit in controlling seizures.
  • Neverthess, it is commonly used for prevention and management of partial and generalized seizures, usually as an adjunctive agent in combination with other anticonvulsants.
  • Phenobarbital is also used for sedation and insomnia although its use for these conditions is now uncommon.
  • Phenobarbital is also used in fixed combinations with other antispasmotics or anticholinergic agents and used for gastrointestinal complaints, including irritable bowel syndrome.

How should this medicine be used?

Recommended dosage: Oral Sedative Dose:

  • Adults: 30 to 120 mg daily in 2 or 3 divided doses.
  • Children: 6 mg/kg of body weight daily in 3 divided doses.

Oral Hypnotic Dose:

  • Adults: 100 to 320 mg.

Oral Anticonvulsant Dose:

  • Adults: 50 to 100 mg 2 or 3 times daily.
  • Children: 15 to 50 mg 2 or 3 times daily.


  • Phenobarbital comes as a tablet and an elixir (liquid) to take by mouth.
  • It is usually taken one to three times a day.
  • If you take phenobarbital for a long time, it may not control your symptoms as well as it did at the beginning of your treatment.
  • Phenobarbital can be habit-forming.
  • Do not take a larger dose, take it more often, or take it for a longer time than prescribed by your doctor.
  • Do not stop taking phenobarbital without talking to your doctor.
  • If you suddenly stop taking phenobarbital, you may experience withdrawal symptoms.

What are the dosage forms and brand names of this medicine?

This medicine is available in fallowing doasage form:

  • As as a tablet and an elixir (liquid).

This medicine is available in fallowing brand namesː

  • Luminal

What side effects can this medication cause?

The most common side effects of this medicine include:

What special precautions should I follow?

  • Phenobarbital may impair the mental and/or physical abilities required for the performance of potentially hazardous tasks, such as driving a car or operating machinery. The patient should be cautioned accordingly.
  • Barbiturates induce liver microsomal enzyme activity. This accelerates the biotransformation of various drugs and is probably part of the mechanism of the tolerance encountered with barbiturates. Phenobarbital, therefore, should be used with caution in patients with decreased liver function.
  • Phenobarbital should also be administered cautiously to patients with a history of drug dependence or abuse.
  • Phenobarbital may decrease the potency of coumarin anticoagulants; therefore, patients receiving such concomitant therapy should have more frequent prothrombin determinations.
  • As with other sedatives and hypnotics, elderly or debilitated patients may react to barbiturates with marked excitement, depression, or confusion.
  • Tell your doctor if you drink or have ever drunk large amounts of alcohol, used street drugs, or overused prescription medications.
  • Older adults should not usually take phenobarbital because it is not as safe or effective as other medications that can be used to treat the same condition.
  • You should know that phenobarbital may decrease the effectiveness of hormonal contraceptives. Talk to your doctor about methods of birth control that will work for you while you are taking phenobarbital.
  • If you are having surgery, including dental surgery, tell the doctor or dentist that you are taking phenobarbital.
  • Alcohol should not be consumed while taking barbiturates. The concurrent use of the barbiturates with other CNS depressants (e.g., alcohol, narcotics, tranquilizers, and antihistamines) may result in additional CNS-depressant effects.
  • Caution should be exercised when phenobarbital is administered to a nursing woman.
  • Phenobarbital has been linked to rare instances of idiosyncratic liver injury that can be severe and even fatal.

What to do in case of emergency/overdose?

Symptoms of overdosage may include:

  • uncontrollable movements of the eyes
  • slowed breathing
  • drop in body temperature
  • blisters
  • loss of coordination
  • drowsiness

Management of overdosage:

  • General management should consist of symptomatic and supportive therapy, including gastric lavage, administration of intravenous fluids, and maintenance of blood pressure, body temperature and adequate respiratory exchange.
  • Dialysis will increase the rate of removal of barbiturates from the body fluids.
  • Antibiotics may be required to control pulmonary complications.

Can this medicine be used in pregnancy?

  • Pregnancy Category B.
  • There are, however, no adequate and well-controlled studies in pregnant women.

Can this medicine be used in children?

  • Phenobarbital is the first-line choice for the treatment of neonatal seizures.

What are the active and inactive ingredients in this medicine?


  • phenobarbital


  • calcium stearate
  • silicon dioxide
  • starch, corn
  • microcrystalline cellulose

Who manufactures and distributes this medicine?

Distr. by:

What should I know about storage and disposal of this medication?

  • Store at 20° to 25°C (68° to 77°F).
  • Protect from light and moisture.
  • Dispense in a tight, light-resistant container as defined in the USP using a child-resistant closure.

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