Phenobarbital is a barbiturate medication that can protect against various types of seizures. In the United States, doctors and healthcare professionals often use it to help treat people with epilepsy.
Besides seizure control, it also has some sedating effects in drug withdrawal. However, the Food and Drug Administration (FDA) does not approve it for this purpose, and it is on the U.S. controlled substance schedule due to its associated risk of misuse, addiction, and overdose.
About phenobarbital

Phenobarbital has been in use for over 100 years to treat seizures in both adults and children.
However, doctors are careful when prescribing this medication as it can make you feel sleepy and dizzy. And, if you use it for a long time, it might become habit-forming.
These side effects can affect your everyday life, but you can help manage them with the right support and advice from a doctor.
How does phenobarbital treat seizures?
Phenobarbital effectively treats partial and generalized seizures by enhancing gamma-aminobutyric acid (GABA), a neurotransmitter that reduces seizure-causing brain activity.
Doctors may prescribe phenobarbital on its own or alongside other seizure medications. It is important to always stick to your prescribed dose.
Altering or stopping phenobarbital without a doctor’s advice may be dangerous.
Is phenobarbital effective?
Phenobarbital is very good at preventing seizures. A 2020 randomized controlled trial showed it to have an 80% success rate in keeping newborns seizure-free.
Like other seizure medications, its effectiveness and side effects need careful monitoring. Healthcare professionals measure its success by looking at how much your seizure frequency reduces and how it affects your daily routine, including managing side effects and maintaining a good quality of life.
What are the side effects?
Understanding the side effects of phenobarbital is crucial for anyone considering or currently using this medication. Some of its unwanted effects are:
- drowsiness and sedation
- difficulty breathing
- dizziness and coordination issues
- concentration and memory difficulties
- irritability or depression
- nausea, vomiting, constipation, and, in rare cases, allergic reaction
Long-term effects can include a change in bone density or skin rashes.
The likelihood and intensity of these side effects can vary from person to person. The key is to balance the seizure control benefits with these potential side effects.
If you are experiencing side effects, it is essential to talk with a doctor about managing them. Together, you can decide whether phenobarbital is the best medication for your condition.
Who should not take phenobarbital?
You should not take phenobarbital if you have:
- an allergy to barbiturates
- a history of substance misuse
- a specific medical condition, like:
- porphyria
- severe respiratory problems
- liver disease
- kidney disease
- congenital long QT syndrome
If possible, you should also avoid this medication if you are pregnant or nursing. Additionally, doctors will typically offer alternative medications to those over the age of 65 years, as phenobarbital may not be as effective or safe.
It is important to note that there is a risk of death if you use phenobarbital alongside alcohol or opiates.
Can you overdose on phenobarbital?
It is important to always stick to your prescribed phenobarbital dosage — taking too much may have very serious and sometimes fatal outcomes.
Symptoms of an overdose often include:
- extreme sleepiness
- confusion
- difficulty breathing
- in severe cases, coma or life threatening conditions
Keep all medications stored securely and out of the reach of children.
If you think you or someone you know has overdosed, it is critical to act fast:
- Call 911 immediately for emergency help or use text-to-911 services if available in your area.
- You can also contact the toll-free Poison Control Center at 800-222-1222 for guidance or use their online web chat for service at the Poison Control Center website.
- Provide details about the medication and when it was ingested.
What should I do if I forget a dose?
If you miss a dose of phenobarbital, and there is only a short time until your next dose, skip the missed dose and continue your regular schedule.
If there is a longer time between doses, take one as soon as you remember, but do not double-dose to make up for the missed one.
Taking phenobarbital on a consistent schedule is essential for seizure control, so you may consider using reminders, like alarms or apps, to keep track. Consult a doctor or healthcare professional if you regularly miss doses.