phenobarbital
Brand names: Luminal
Phenobarbital is a medicine that can help control seizures and calm you down. It belongs to a class of drugs called barbiturates.
Drug Shortage Alert
phenobarbital is currently listed as to be discontinued by the FDA. Affected manufacturer: Endo Pharmaceuticals, Inc..
View all drug shortages →Drug Pricing (NADAC)
Generic Price
$0.24/unit
Generic Available
Yes (0 manufacturers)
Pricing data from NADAC (CMS), effective December 18, 2024. Compare all drug costs →
What it does
This medicine is used to treat generalized and partial seizures.
Common side effects
Drowsiness, Sedation, Lethargy
Key warnings
You should not take this medicine if you are allergic to barbiturates.
How It Works
Phenobarbital works by slowing down the activity of your brain and nervous system. It increases the effects of a natural chemical in the body called GABA. This helps to reduce seizures and promote relaxation.
How to Take It
Take phenobarbital exactly as your doctor tells you. Your doctor will decide the right dose for you based on your age, weight, and health. It is important to follow their instructions carefully.
Pregnancy & Breastfeeding
Tell your doctor if you are pregnant or plan to become pregnant. Phenobarbital can harm an unborn baby. Talk to your doctor about the risks and benefits of taking this medicine while breastfeeding.
Missed Dose
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 and continue with your regular schedule.
Storage
Keep this medicine tightly closed and store it at room temperature (68° - 77°F).
Side Effects (from patient reports)
Based on 8,705 FDA adverse event reports.
FDA Adverse Event Report Analysis
Detailed analysis of 13,998 reports from the FDA Adverse Event Reporting System (FAERS). Reports span 2004–2025.
Total Reports
13,998
Death-Related Reports
1,733
Hospitalization Reports
5,401
Top Indication
Product Used For Unknown Indication
Gender Distribution
Age Distribution
Most Reported Adverse Reactions (FAERS)
| # | Reaction | Reports |
|---|---|---|
| 1 | DRUG INEFFECTIVE | 2,389 |
| 2 | SEIZURE | 1,534 |
| 3 | OFF LABEL USE | 1,358 |
| 4 | DRUG INTERACTION | 635 |
| 5 | TOXICITY TO VARIOUS AGENTS | 621 |
| 6 | STATUS EPILEPTICUS | 482 |
| 7 | MULTIPLE-DRUG RESISTANCE | 442 |
| 8 | SOMNOLENCE | 433 |
| 9 | CONDITION AGGRAVATED | 413 |
| 10 | EPILEPSY | 397 |
| 11 | FALL | 397 |
| 12 | HYPOTENSION | 391 |
| 13 | PYREXIA | 377 |
| 14 | PRODUCT USE IN UNAPPROVED INDICATION | 374 |
| 15 | CONVULSION | 369 |
Reactions in Death Reports
Reactions in Hospitalization Reports
Source: FDA FAERS (Adverse Event Reporting System) FDA FAERS (Adverse Event Reporting System) Reports are voluntary and do not establish causation
Serious Warnings
You should not take this medicine if you are allergic to barbiturates. Also, do not take it if you have a history of porphyria, severe liver problems, or breathing problems.
Known Drug Interactions
Anticonvulsants carbamazepine , phenobarbital, primidone, phenytoin ↓ nirmatrelvir/ritonavir Co-administration contraindicated due to potential loss of virologic response and possible resistance [see Contraindications (4) ] .
Mechanism: Phenobarbital speeds up how fast your body breaks down the antiviral, which lowers the amount of medicine in your blood. This can stop the treatment from working and might lead to drug resistance.
What to do: This combination is not recommended and should be avoided. Talk to your provider about using a different medication.
CYP3A Inducers Do not use ranolazine with CYP3A inducers such as rifampin, rifabutin, rifapentine, phenobarbital, phenytoin, carbamazepine, and St.
Mechanism: Phenobarbital triggers your liver to process ranolazine too quickly, meaning there won't be enough medicine in your blood.
What to do: Do not take these two drugs together.
Carbamazepine (CYP450 Induction) Not Studied In Vivo or In Vitro , but Likely to Result in Significant Reduction Contraindicated Long Acting Barbiturates (e.g., phenobarbital, mephobarbital) (CYP450 Induction) Not Studied In Vivo or In Vitro , but Likely to Result in Significant Reduction Contraindicated Phenytoin (CYP450 Induction) Significantly Reduced Increase voriconazole maintenance dose from 4 mg/kg to 5 mg/kg IV every 12 hours or from 200 mg to 400 mg orally every 12 hours (100 mg to 200 mg orally every 12 hours in patients weighing less than 40 kg).
Mechanism: Phenobarbital causes the body to process voriconazole much faster than normal, which significantly lowers the amount of medicine in your system. This makes the treatment much less likely to fight off an infection.
What to do: This combination is contraindicated and should be avoided. Talk to your doctor about using a different medication that does not interfere with your treatment.
Examples: Rifampin, phenytoin, phenobarbital, ritonavir Insulin or Insulin Secretagogues Clinical Impact: The risk of hypoglycemia is increased when INVOKANA is used concomitantly with insulin secretagogues (e.g., sulfonylurea) or insulin.
Mechanism: Phenobarbital speeds up the breakdown of canagliflozin in your body, which can make the diabetes medicine less effective.
What to do: Monitor your blood sugar levels regularly and consult your doctor about potential dosage changes.
( 7.1 ) Phenobarbital and Clobazam: Reduce dosage as needed when used concomitantly with XCOPRI. phenobarbital ↑ plasma concentrations Because of a potential for an increase in the risk of adverse reactions from these drugs, consider a reduction in dosage of phenobarbital or clobazam, as clinically appropriate, when used concomitantly with XCOPRI.
Mechanism: Cenobamate causes the levels of phenobarbital in your blood to go up. This makes it more likely that you will have a bad reaction to the phenobarbital.
What to do: Your doctor may need to lower your dose of phenobarbital to keep you safe while you take cenobamate.
Common Questions
Can I drink alcohol while taking phenobarbital?
Will phenobarbital cure my seizures?
How long does it take for phenobarbital to start working?
Can I stop taking phenobarbital suddenly?
Does phenobarbital interact with other medications?
Can phenobarbital cause mood changes?
What should I do if I experience side effects?
Can children take phenobarbital?
Will phenobarbital make me feel tired?
Can I drive while taking phenobarbital?
What are the common side effects of phenobarbital?
Does phenobarbital interact with other medications?
What drug class is phenobarbital?
Is phenobarbital safe during pregnancy?
Has phenobarbital been recalled?
Is phenobarbital currently in shortage?
Active Recalls
Lack of Assurance of Sterility: FDA inspection findings resulted in concerns regarding quality control processes
Lowlite Investments, Inc. D/B/A Olympia Pharmacy
Related Medications in Anticonvulsant (Barbiturate)
Other drugs grouped near phenobarbital — same-class peers and common alternatives.
brivaracetam
Briviact
Brivaracetam is a medicine used to treat partial-onset seizures.
Compare with phenobarbital →
cannabidiol
Epidiolex
Epidiolex is a medicine that contains cannabidiol.
Compare with phenobarbital →
carbamazepine
Tegretol
Carbamazepine is a medicine used to control seizures and treat nerve pain.
Compare with phenobarbital →
cenobamate
Xcopri
Xcopri is a medicine used to treat partial-onset seizures in adults.
Compare with phenobarbital →
clobazam
Onfi, Sympazan
Clobazam oral suspension is a medicine used with other medicines to treat seizures caused by Lennox-Gastaut syndrome.
Compare with phenobarbital →
Medication Guides
Understanding Drug Interactions
How CYP450 enzymes, inhibitors, and inducers affect your medications
Generic vs Brand Name Drugs
FDA requirements, cost savings, and when the difference matters
Narrow Therapeutic Index Drugs
Why some drugs demand precise dosing and monitoring
Common Drug Interactions
Dangerous medication combinations and how to protect yourself
Related Health & Safety Data
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What the FDA Data Shows for phenobarbital
The FDA label for phenobarbital (sold under brand names such as Luminal) classifies it as a prescription-only medication in the Anticonvulsant (Barbiturate) class. This medicine is used to treat generalized and partial seizures. Official labeling lists 4 commonly reported side effects, including Drowsiness, Sedation, Lethargy.
Post-market surveillance from the FDA Adverse Event Reporting System (FAERS) captures real-world experience. For this drug, FAERS contains 8,705 voluntary reports. The database also lists 59 documented drug interactions derived from FDA labeling, with the top-flagged interaction rated major severity. NADAC pricing from CMS shows a generic unit cost of $0.24.
Report counts do not establish causation — a FAERS entry documents a temporal association, not proof that the drug produced the outcome. Widely prescribed medications naturally accumulate more reports than niche therapies, so raw totals must be interpreted alongside total exposure. Shortage status, recall history (currently 1 recall record on file), and patent information further shape supply and switching decisions. This page summarizes public FDA data for educational purposes only and is not a substitute for professional medical advice — always consult a licensed healthcare provider before starting, stopping, or changing any medication.
Data Sources
Drug labeling: FDA Drug Labels (SPL/DailyMed). Adverse events: FDA Adverse Event Reporting System (FAERS). Pricing: CMS National Average Drug Acquisition Cost (NADAC). Shortage status: FDA Drug Shortages Database.
FAERS reports are voluntary and do not establish causation. Drug interactions are derived from FDA labeling and clinical references. Always consult a healthcare professional before making medication decisions.
Last updated: January 5, 2022
Read our methodology — how this data is sourced, computed, and verified.
All federal data sources used on this page
- FDA Orange Book — approved drug products with therapeutic equivalence. accessdata.fda.gov/cder/ob
- FDA DailyMed — NIH-hosted drug labeling for FDA-approved meds. dailymed.nlm.nih.gov
- FDA Adverse Event Reporting System (FAERS) — post-marketing safety surveillance. fda.gov/drugs/faers
- NLM RxNorm — standardized clinical drug nomenclature. nlm.nih.gov/research/umls/rxnorm
- CMS Medicare Part B Drug Average Sales Price Files — federal drug pricing data. cms.gov/medicare/part-b-drugs/asp
- FDA Drug Shortages Database — current and resolved drug shortage tracking. accessdata.fda.gov/drugshortages