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Phenobarbital Coupon - Phenobarbital 64.8mg tablet

phenobarbital

Generic Luminal
Used for Epilepsy, Sedation

Phenobarbital is a barbiturate that helps control seizures and can also be used for sedation. The medication comes as a tablet and oral liquid, and the dose depends on your age, weight, condition, and response to treatment. Phenobarbital is a controlled substance because it can lead to misuse, dependence, and withdrawal. Common side effects include sleepiness, dizziness, and problems with balance or coordination.

Reviewed by:
reviewerRobert Chad Hakim, PharmD, BCCCP
reviewerDaisy Chau, PharmD
Last reviewed on September 4, 2026
basics-icon

What is Phenobarbital?

What is Phenobarbital used for?

How Phenobarbital works

Phenobarbital is a barbiturate. It works by increasing the effects of gamma-aminobutyric acid (GABA), a chemical that slows activity in the brain. This helps prevent seizures and produces a calming, sedative effect.

When does Phenobarbital start working?Time passed since treatment started:
MINUTES
Initial effect
HOURS
Full effect
DAYS
WEEKS
MONTHS

Drug facts

Common BrandsLuminal(brand no longer available)
Drug ClassBarbiturate
Controlled Substance ClassificationSchedule IV
Generic StatusLower-cost generic available
AvailabilityPrescription only
warnings-icon

Risks and warnings for Phenobarbital

Phenobarbital can cause some serious health issues. This risk may be even higher for certain groups. If this worries you, talk to your doctor or pharmacist about other options.

Dependence and withdrawal

  • Risk factors: Long-term use of phenobarbital | Higher doses of phenobarbital | History of substance misuse | Stopping phenobarbital suddenly

Phenobarbital can cause tolerance and dependence, especially with higher doses or long-term use. Take it exactly as prescribed, since misuse can raise your risk of serious side effects, including dangerously slow breathing.

Don’t suddenly stop taking phenobarbital, because this can cause life-threatening withdrawal symptoms, including confusion, seizures, and delirium. If you need to stop treatment, your prescriber will usually lower your dose slowly to help prevent withdrawal.

Dangerously slow breathing (respiratory depression)

  • Risk factors: Taking medications that can cause slow breathing | Drinking alcohol | Older age | Lung or breathing problems | Taking too much phenobarbital

Phenobarbital slows activity in your brain and can cause dangerously slow breathing. Drinking alcohol or taking other medications that cause sleepiness, such as benzodiazepines, opioids, or muscle relaxants, can make these effects stronger and potentially life-threatening. Make sure your loved ones know to call 911 if you have very slow or shallow breathing, can’t be woken, or have bluish-colored lips, fingers, or toes.

Extreme excitement

  • Risk factors: History of short-term or long-term pain | Older age | Younger age | Have poor health

Phenobarbital can sometimes make you feel agitated, excited, or confused instead of sleepy or calm. This is more likely in children, older adults, and people with short-term or long-term pain. Tell your prescriber if you notice these effects while taking the medication.

Harm to unborn babies

Phenobarbital can harm an unborn baby and cause withdrawal symptoms in newborns when taken during pregnancy. But suddenly stopping seizure treatment can also be dangerous, so talk to your prescriber about the risks and benefits of treatment if you’re pregnant or planning to become pregnant.

If you take phenobarbital during pregnancy, consider enrolling in the North American Antiepileptic Drug (NAAED) Pregnancy Registry to help researchers learn more about the safety of seizure medications during pregnancy.

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Side effects of Phenobarbital

The following side effects may get better over time as your body gets used to the medication. Let your healthcare provider know immediately if you continue to experience these symptoms or if they worsen over time.

Common Side Effects

  • Sleepiness
  • Dizziness
  • Poor balance or coordination

Less Common Side Effects

  • Nausea
  • Vomiting
  • Constipation
  • Headache
  • Slowed heart rate
  • Fainting
  • Confusion

Phenobarbital serious side effects

Contact your healthcare provider immediately if you experience any of the following.

  • Dangerously slowed breathing: extreme sleepiness, slow or shallow breathing, trouble waking up, confusion, blue or gray lips or skin
  • Severe skin reactions: painful rash, blisters, peeling skin, mouth sores, fever
  • Serious allergic reactions: hives, swelling of the face or throat, trouble breathing, trouble swallowing
When do Phenobarbital possible side effects begin and end?
Time passed since treatment started:
H
D
W
M
Risk of sleepiness
Risk of dizziness
Risk of confusion
If a line continues to the right, you'll likely keep experiencing this side effect once it starts.

Source: DailyMed

The following Phenobarbital side effects have also been reported

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur:

Rare

Confusion (especially in the elderly)

dizziness, lightheadedness that continues, or fainting

eye pain

skin rash or hives

Incidence not known

Cough

difficulty with swallowing

fast irregular, pounding, or racing heartbeat or pulse

fever

hives or welts

hoarseness

irritation

itching skin

joint pain, stiffness, or swelling

puffiness or swelling of the eyelids or around the eyes, face, lips, or tongue

redness of the skin

shortness of breath

skin rash

tightness in the chest

trouble with breathing

wheezing

Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common

Constipation

decreased sweating

dryness of the mouth, nose, throat, or skin

Less common or rare

Bloated feeling

blurred vision

difficult urination

difficulty with swallowing

drowsiness

false sense of well-being

headache

increased sensitivity of eyes to light

loss of memory

nausea or vomiting

redness or other signs of irritation at the place of injection

trouble with sleeping

unusual tiredness or weakness

Incidence not known

Decreased interest in sexual intercourse

inability to have or keep an erection

loss in sexual ability, desire, drive, or performance

loss of taste

For patients using scopolamine:

After you stop using scopolamine, your body may need time to adjust. The length of time this takes depends on the amount of scopolamine you were using and how long you used it. During this period of time check with your doctor if you notice any of the following side effects:

Anxiety

irritability

nightmares

pupil of one eye is larger (patch only)

sensitivity of eyes to light (patch only)

trouble in sleeping

Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.

Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

See more Phenobarbital side effects
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pros-and-cons-icon

Pros and cons of Phenobarbital

Pros

  • Treats both generalized and partial seizures
  • Can be used in adults and children
  • Available as tablets and oral liquid

Cons

  • Can cause physical dependence and withdrawal
  • Interacts with many medications
  • Not safe during pregnancy or breastfeeding
pharmacist-tips-icon

Pharmacist tips for Phenobarbital

pharmacist
  • You can take phenobarbital with or without food. If it upsets your stomach, try taking it with food.
  • You might be able to crush or cut phenobarbital tablets if you have trouble swallowing them. Check with your pharmacist first to make sure your specific tablets can be crushed or cut safely. An oral liquid is also available if you have trouble swallowing tablets.
  • Keep your appointments for checkups and blood tests while taking phenobarbital. Your prescriber might check the medication level in your blood to help find the right dose for you.
  • Phenobarbital can cause sleepiness, dizziness, spinning sensations, and problems with movement or coordination, especially when you first start treatment or after a dose increase. Tell your prescriber if they’re severe or don’t get better.
  • Phenobarbital can interact with many medications, including phenytoin, doxycycline, and warfarin. Tell your prescriber and pharmacist about everything you take so they can check for interactions.
  • Avoid alcohol while taking phenobarbital. Combining them can cause severe sleepiness, poor coordination, and dangerously slow breathing.
  • Don’t change your dose or suddenly stop taking phenobarbital without talking to your prescriber. This can cause withdrawal symptoms, including seizures, anxiety, and trouble sleeping. Your prescriber can help you lower your dose slowly when it’s time to stop treatment.
  • Phenobarbital can make hormonal birth control less effective, which can lead to an unplanned pregnancy. Talk to your prescriber about which birth control options are best for you and whether you need a backup method.
  • Taking too much phenobarbital can cause a serious overdose. Tell your loved ones to get emergency medical help right away if you’re difficult to wake, have slow or shallow breathing, become confused, or lose consciousness.
  • Pregnancy: Phenobarbital can harm an unborn baby and cause withdrawal symptoms in newborns. Tell your prescriber if you’re pregnant or planning to become pregnant.
  • Breastfeeding: Phenobarbital can pass into breast milk and might cause sleepiness or feeding problems in your baby. Talk to your prescriber about the risks and benefits of breastfeeding while taking this medication.

Phenobarbital oral liquid

  • Shake the oral liquid well before each dose. This helps make sure the medication is evenly mixed.
  • Use an oral syringe or medication dosing cup to measure your dose of the oral liquid. Don't use household spoons because they might not measure the correct amount.
  • Storage: Keep the oral liquid at room temperature in the original bottle.
dosage-icon

Phenobarbital dosage

The average cost for 60 tablets of 64.8mg of Phenobarbital is $17.98 with a free GoodRx coupon.
ml of elixirMl of elixir
DosageQuantityPrice as low asPrice per unit
20mg/5ml120 ml$13.04$0.11
tabletTablet
DosageQuantityPrice as low asPrice per unit
16.2mg60 tablets$13.90$0.23
32.4mg60 tablets$17.64$0.29
64.8mg60 tablets$17.98$0.30
97.2mg60 tablets$21.76$0.36
60mg60 tablets$10.24$0.17
100mg60 tablets$12.79$0.21
15mg60 tablets$14.18$0.24
30mg60 tablets$14.97$0.25
See more Phenobarbital dosage
interactions-icon

Interactions between Phenobarbital and other drugs

Phenobarbital may interact with certain medications or supplements. Always let your doctor and pharmacist know about any other medications or supplements (including prescribed and over-the-counter medications, vitamins, and dietary or herbal supplements) that you are currently taking. The list below does not include all possible drug interactions with Phenobarbital. Please note that only the generic name of each medication is listed below.

Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking any of these medicines, it is especially important that your healthcare professional know if you are taking any of the medicines listed below. The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.

Using medicines in this class with any of the following medicines is not recommended. Your doctor may decide not to treat you with a medication in this class or change some of the other medicines you take.

Using medicines in this class with any of the following medicines is usually not recommended, but may be required in some cases. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.

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How much does Phenobarbital cost?

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Phenobarbital (generic)
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$10.24

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contraindications-icon

Phenobarbital contraindications

Contraindications are specific health conditions or situations in which a person should not take a medication due to safety concerns. If you have any of the following conditions or if any of the following apply to you, let your healthcare provider know because Phenobarbital will not be safe for you to take.

  • Allergy to barbiturates
  • History of porphyria
  • Severe liver problems
  • Breathing condition that causes shortness of breath or blocked airways
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What are alternatives to Phenobarbital?

There are a number of medications that your doctor can prescribe in place of Phenobarbital. Compare a few possible alternatives below.
Phenobarbital
Used for:
$10.24Lowest GoodRx priceView prices
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$13.47Lowest GoodRx priceView prices
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$13.52Lowest GoodRx priceView prices
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News about Phenobarbital

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Phenobarbital images

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References

Best studies we found

American Society of Addiction Medicine. (2020). The ASAM clinical practice guideline on alcohol withdrawal management.

Ajenat Pharmaceuticals. (2025). PHENOBARBITAL oral solution [package insert]. DailyMed.

Centers for Disease Control and Prevention. (2018). Spoons are for soup / Milliliters (mL) are for medicine.

GoodRx Health has strict sourcing policies and relies on primary sources such as medical organizations, governmental agencies, academic institutions, and peer-reviewed scientific journals. Learn more about how we ensure our content is accurate, thorough, and unbiased by reading our editorial guidelines.