What Is Phenobarbital?

Phenobarbital is a medication that belongs to a class of drugs called barbiturates. It has been used in medicine for over 100 years, making it one of the oldest seizure medications still in use today. Despite its age, Phenobarbital remains one of the most widely prescribed anticonvulsants in the world — particularly in developing countries where newer medications may not be affordable or available.

In the United States, Phenobarbital is classified as a Schedule IV controlled substance by the DEA, which means it has a recognized medical use but also carries some potential for dependence.

Phenobarbital was originally sold under the brand names Luminal and Solfoton, but today it is almost exclusively available as a generic medication.

What Is Phenobarbital Used For?

Phenobarbital is FDA-approved for several conditions:

• Seizure disorders (epilepsy) — This is the primary use. Phenobarbital can treat many types of seizures, including generalized tonic-clonic seizures and partial seizures.
• Status epilepticus — A life-threatening condition where seizures do not stop. Phenobarbital can be given intravenously in emergency settings.
• Short-term sedation — Phenobarbital may be used briefly for insomnia, though this is less common today.
• Short-term anxiety relief — Rarely used for this purpose in modern medicine.

Doctors also prescribe Phenobarbital "off-label" (for uses not specifically FDA-approved) for:

• Alcohol withdrawal management
• Benzodiazepine withdrawal
• Neonatal abstinence syndrome (helping newborns withdraw from substances)
• Neonatal seizures

To understand how Phenobarbital works in the brain, read: How Does Phenobarbital Work? Mechanism of Action Explained.

Available Forms and Strengths

Phenobarbital comes in several forms:

• Oral tablets — Available in 15 mg, 16.2 mg, 30 mg, 32.4 mg, 60 mg, 64.8 mg, 97.2 mg, and 100 mg strengths
• Oral elixir (liquid) — 20 mg per 5 mL, useful for children or adults who have difficulty swallowing pills
• Injectable solution — 65 mg/mL and 130 mg/mL for intramuscular or intravenous use in hospitals and emergency settings

How to Take Phenobarbital

Always follow your doctor's instructions exactly. General guidelines include:

• Take Phenobarbital by mouth 1 to 3 times daily as directed by your doctor.
• You can take it with or without food. Taking it with food may help if it upsets your stomach.
• Take it at the same time(s) every day to maintain steady levels in your blood.
• Never stop taking Phenobarbital suddenly. Abrupt discontinuation can cause dangerous withdrawal symptoms, including rebound seizures. If you need to stop, your doctor will gradually reduce your dose over time.
• If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose. Do not double up.

Typical Dosage

Dosage varies based on the condition being treated, your age, weight, and how you respond to the medication:

• Seizures (adults): 60 to 200 mg per day, taken in 1 to 3 divided doses
• Sedation (adults): 30 to 120 mg per day
• Status epilepticus (emergency): 15 mg/kg IV loading dose
• Children: Dosing is based on weight and is determined by the prescribing doctor

Your doctor may adjust your dose based on blood level testing. Therapeutic blood levels for Phenobarbital are typically 15 to 40 mcg/mL.

Important Safety Information

Who Should NOT Take Phenobarbital

Phenobarbital is not safe for everyone. It should not be used if you have:

• Porphyria — A group of rare disorders affecting the blood. Phenobarbital can trigger dangerous attacks.
• Severe respiratory disease — Phenobarbital can depress breathing.
• Severe liver disease — The medication is processed by the liver.
• Known allergy to barbiturates

Pregnancy and Breastfeeding

Phenobarbital is Pregnancy Category D, meaning it may harm an unborn baby. However, stopping seizure medication during pregnancy can also be dangerous. If you are pregnant or planning to become pregnant, talk to your doctor about the risks and benefits. Phenobarbital does pass into breast milk, so breastfeeding mothers should be monitored closely.

Older Adults

Phenobarbital is listed on the Beers Criteria as a medication that older adults should generally avoid due to increased sensitivity, fall risk, and cognitive side effects.

Common Side Effects

The most frequently reported side effects include:

• Drowsiness
• Dizziness
• Headache
• Nausea or vomiting
• Excitement or hyperactivity (especially in children)

For a detailed guide on side effects and when to seek help, read: Phenobarbital Side Effects: What to Expect and When to Call Your Doctor.

Drug Interactions

Phenobarbital interacts with many other medications because it is a powerful enzyme inducer — it speeds up how your liver processes other drugs. This can reduce the effectiveness of:

• Blood thinners (Warfarin)
• Birth control pills
• Corticosteroids
• Many other medications

It also has dangerous additive effects when combined with alcohol, opioids, or benzodiazepines. For the full list, see: Phenobarbital Drug Interactions: What to Avoid.

Cost and Availability in 2026

Phenobarbital is available only as a generic, which keeps costs relatively low. Typical cash prices range from $8 to $63 for 60 tablets, depending on the strength and pharmacy. With discount cards, prices can be as low as $8 to $28.

Most insurance plans cover Phenobarbital as a Tier 1 or Tier 2 generic. Prior authorization is generally not required for epilepsy.

However, because Phenobarbital is a controlled substance with limited manufacturers, supply can be inconsistent at some pharmacies. If you are having trouble finding it, check out: How to Check If a Pharmacy Has Phenobarbital in Stock.

For savings tips, read: How to Save Money on Phenobarbital.

Is Phenobarbital Still a Good Treatment Option?

Yes. Despite being over a century old, Phenobarbital remains effective and affordable. It is still recommended by the World Health Organization as an essential medicine for epilepsy. While newer anticonvulsants exist with potentially fewer side effects, Phenobarbital works well for many patients — especially those who have been stable on it for years.

If you are considering alternatives, talk to your doctor and read: Alternatives to Phenobarbital If You Can't Fill Your Prescription.

The Bottom Line

Phenobarbital is a time-tested seizure medication that remains widely used in 2026. It is affordable, effective, and available as a generic. Like all medications, it comes with risks and side effects that you should discuss with your doctor. Take it exactly as prescribed, never stop suddenly, and stay informed about potential interactions.

Need help finding Phenobarbital? MedFinder can help you locate it at a pharmacy near you.