pharmacopeia
GET
/api/v1/drug/phenobarbital
2D structure
5-ethyl-5-phenyl-1,3-diazinane-2,4,6-trione
SMILES CCC1(C(=O)NC(=O)NC1=O)C2=CC=CC=C2
InChIKey DDBREPKUVSBGFI-UHFFFAOYSA-N

Mechanism of action

Sourced from openFDA

Mechanism-of-action class: Neurotransmitter Transporter Interactions.

Indications

Sourced from openFDA
  • Sedative Anticonvulsant- For the treatment of generalized and partial seizures.ICD-10: G40.909

Contraindications

Sourced from openFDA
  • Phenobarbital is contraindicated in patients who are hypersensitive to barbiturates, in patients with a history of manifest or latent porphyria, and in patients with marked impairment of liver function or respiratory disease in which dyspnea or obstruction is evident.contraindicated

Dosage & administration

Sourced from openFDA

The dose of phenobarbital must be individualized with full knowledge of its particular characteristics. Factors of consideration are the patient's age, weight, and condition. ADVERSE REACTIONS The following adverse reactions have been reported: CNS Depression- Residual sedation or "hangover," drowsiness, lethargy, and vertigo. Emotional disturbances and phobias may be accentuated. In some persons, barbiturates such as phenobarbital repeatedly produce excitement rather than depression, and the patient may appear to be inebriated. Irritability and hyperactivity can occur in children. Like other nonanalgesic hypnotic drugs, barbiturates such as phenobarbital, when given in the presence of pain, may cause restlessness, excitement, and even delirium. Rarely, the use of barbiturates results in localized or diffuse myalgic, neuralgic, or arthritic pain, especially in psychoneurotic patients with insomnia. The pain may appear in paroxysms, is most intense in the early morning hours, and is most frequently located in the region of the neck, shoulder girdle, and upper limbs. Symptoms may last for days after the drug is discontinued. Respiratory/Circulatory- Respiratory depression, apnea, circulatory collapse. Allergic- Acquired hypersensitivity to barbiturates consists chiefly in allergic reactions that occur especially in persons who tend to have asthma, urticaria, angioedema, and similar conditions. Hypersensitivity reactions in this category include localized swelling, particularly of the eyelids, cheeks, or lips, and erythematous dermatitis.

Warnings & precautions

Sourced from openFDA

1. Habit-Forming Phenobarbital may be habit-forming. Tolerance and psychological and physical dependence may occur with continued use ( see Drug Abuse and Dependence and Pharmacokinetics under Clinical Pharmacology ). Patients who have psychologic dependence on barbiturates may increase the dosage or decrease the dosage interval without consulting a physician and may subsequently develop a physical dependence on barbiturates. In order to minimize the possibility of overdosage or the development of dependence, the prescribing and dispensing of sedative-hypnotic barbiturates should be limited to the amount required for the interval until the next appointment. Abrupt cessation after prolonged use in a person who is dependent on the drug may result in withdrawal symptoms, including delirium, convulsions, and possibly death. Barbiturates should be withdrawn gradually from any patient known to be taking excessive doses over long periods of time ( see Drug Abuse and Dependence ). 2. Acute or Chronic Pain Caution should be exercised when barbiturates are administered to patients with acute or chronic pain, because paradoxical excitement could be induced or important symptoms could be masked. However, the use of barbiturates as sedatives in the postoperative surgical period and as adjuncts to cancer chemotherapy is well established. 3. Usage in Pregnancy Barbiturates can cause fetal damage when administered to a pregnant woman.

Adverse reactions

Sourced from openFDA

The following adverse reactions have been reported: CNS Depression- Residual sedation or "hangover," drowsiness, lethargy, and vertigo. Emotional disturbances and phobias may be accentuated. In some persons, barbiturates such as phenobarbital repeatedly produce excitement rather than depression, and the patient may appear to be inebriated. Irritability and hyperactivity can occur in children. Like other nonanalgesic hypnotic drugs, barbiturates such as phenobarbital, when given in the presence of pain, may cause restlessness, excitement, and even delirium. Rarely, the use of barbiturates results in localized or diffuse myalgic, neuralgic, or arthritic pain, especially in psychoneurotic patients with insomnia. The pain may appear in paroxysms, is most intense in the early morning hours, and is most frequently located in the region of the neck, shoulder girdle, and upper limbs. Symptoms may last for days after the drug is discontinued. Respiratory/Circulatory- Respiratory depression, apnea, circulatory collapse. Allergic- Acquired hypersensitivity to barbiturates consists chiefly in allergic reactions that occur especially in persons who tend to have asthma, urticaria, angioedema, and similar conditions. Hypersensitivity reactions in this category include localized swelling, particularly of the eyelids, cheeks, or lips, and erythematous dermatitis. Rarely, exfoliative dermatitis (eg, Stevens-Johnson syndrome and toxic epidermal necrolysis) may be caused by phenobarbital and can prove fatal.

Use in specific populations

Sourced from openFDA

3. Usage in Pregnancy Barbiturates can cause fetal damage when administered to a pregnant woman. Retrospective, case-controlled studies have suggested a connection between the maternal consumption of barbiturates and a higher than expected incidence of fetal abnormalities. Barbiturates readily cross the placental barrier and are distributed throughout fetal tissues; the highest concentrations are found in the placenta, fetal liver and brain. Fetal blood levels approach maternal blood levels following parenteral administration. Withdrawal symptoms occur in infants born to women who receive barbiturates throughout the last trimester of pregnancy ( see Drug Abuse and Dependence ). If phenobarbital is used during pregnancy or if the patient becomes pregnant while taking this drug, the patient should be apprised of the potential hazard to the fetus.

Pharmacokinetics

Sourced from openFDA
Metabolism
Barbiturates are absorbed in varying degrees following oral or parenteral administration. The salts are more rapidly absorbed than are the acids.

Overdosage

Sourced from openFDA

Signs and Symptoms The onset of symptoms following a toxic oral exposure to phenobarbital may not occur until several hours following ingestion. The toxic dose of barbiturates varies considerably. In general, an oral dose of 1 g of most barbiturates produces serious poisoning in an adult. Death commonly occurs after 2 to 10 g of ingested barbiturate. The sedated, therapeutic blood levels of phenobarbital range between 5 to 40 µg/mL; the usual lethal blood level ranges from 100 to 200 µg/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. The manifestations of long-acting barbiturate in overdose include nystagmus, ataxia, CNS depression, respiratory depression, hypothermia, and hypotension. Other findings may include absent or depressed reflexes and erythematous or hemorrhagic blisters (primarily at pressure points). Following massive exposure to phenobarbital, pulmonary edema, circulatory collapse with loss of peripheral vascular tone, cardiac arrest, and death may occur.

Approval history

Sourced from openFDA
  • Nov 17, 2022NDANDA215910Sun Pharm Inds Inc

FDA shortages

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Reference statistics from the openFDA drug-shortage dataset. For a live view, consult the FDA database directly. Not clinical guidance.

  • Phenobarbital, Tablet, 16.2 mg (NDC 0603-5165-21)To be discontinued
    Sponsor: Endo Pharmaceuticals, Inc.
    Updated
  • Phenobarbital, Tablet, 16.2 mg (NDC 0603-5165-32)To be discontinued
    Sponsor: Endo Pharmaceuticals, Inc.
    Updated
  • Phenobarbital, Tablet, 32.4 mg (NDC 0603-5166-21)To be discontinued
    Sponsor: Endo Pharmaceuticals, Inc.
    Updated
  • Phenobarbital, Tablet, 32.4 mg (NDC 0603-5166-32)To be discontinued
    Sponsor: Endo Pharmaceuticals, Inc.
    Updated
  • Phenobarbital, Tablet, 64.8 mg (NDC 0603-5167-21)To be discontinued
    Sponsor: Endo Pharmaceuticals, Inc.
    Updated
  • Phenobarbital, Tablet, 64.8 mg (NDC 0603-5167-32)To be discontinued
    Sponsor: Endo Pharmaceuticals, Inc.
    Updated
  • Phenobarbital, Tablet, 97.2 mg (NDC 0603-5168-21)To be discontinued
    Sponsor: Endo Pharmaceuticals, Inc.
    Updated
  • Phenobarbital, Tablet, 97.2 mg (NDC 0603-5168-32)To be discontinued
    Sponsor: Endo Pharmaceuticals, Inc.
    Updated

FAERS reports

View JSON
Reference statistics only. FAERS reports are voluntarily submitted and are not incidence rates, safety signals, or causal evidence. Counts reflect reporting volume — how often a reaction was reported, not how often it occurs. For decision-grade use, consult openFDA and the FAERS Public Dashboard directly.
15,485 total reports matchedLatest report Share = reports listing the reaction ÷ total matched reports. Rows can sum to >100% because a single report often lists multiple reactions.
  1. 1Drug Ineffective2,53716%
  2. 2Seizure1,63611%
  3. 3Off Label Use1,4729.5%
  4. 4Drug Interaction6534.2%
  5. 5Toxicity To Various Agents6404.1%
  6. 6Status Epilepticus5103.3%
  7. 7Somnolence4763.1%
  8. 8Multiple-drug Resistance4663.0%
  9. 9Fall4593.0%
  10. 10Epilepsy4312.8%
  11. 11Condition Aggravated4302.8%
  12. 12Hypotension4162.7%
  13. 13Pyrexia4152.7%
  14. 14Fatigue4052.6%
  15. 15Product Use In Unapproved Indication3972.6%

Literature

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Recent PubMed references pinned to Phenobarbital as a MeSH major topic. Citations link to pubmed.ncbi.nlm.nih.gov.

Clinical trials

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The 10 most recently updated of 66 ClinicalTrials.gov registrations naming Phenobarbital as an intervention. Registration is not evidence of efficacy or safety — reference crosswalk only.

Frequently asked questions

How does Phenobarbital work?
Mechanism-of-action class: Neurotransmitter Transporter Interactions.
What is Phenobarbital used for?
According to FDA labeling, Phenobarbital carries indications including: Sedative Anticonvulsant- For the treatment of generalized and partial seizures.. This is a reference summary of labeled uses, not medical advice or a treatment recommendation.
What class of drug is Phenobarbital?
Phenobarbital is classified as Barbiturates and derivatives, Neurotransmitter Transporter Interactions, Electrical Activity Alteration.
What are the brand names for Phenobarbital?
Phenobarbital is marketed under brand names including Donnatal, Fidoquel, Phenohytro, Sezaby.
What are the contraindications for Phenobarbital?
Phenobarbital labeling lists contraindications including: Phenobarbital is contraindicated in patients who are hypersensitive to barbiturates, in patients with a history of manifest or latent porphyria, and in patients with marked impairment of liver function or respiratory disease in which dyspnea or obstruction is evident.. Always consult the full prescribing information and a clinician.
Note. Data for phenobarbital is illustrative MVP content compiled from public sources. pharmacopeia is for educational and informational use only and is not a substitute for professional medical advice.

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