In the world of seizure medications, phenobarbital is one of the founding fathers. It’s been around since 1912 and is the oldest epilepsy medication still in use. It can treat and prevent a range of seizure types in both children and adults.
Phenobarbital, which belongs to a class of medications called barbiturates, works on certain chemicals in the body that calm brain activity, says Jacqueline French, MD, chief medical and innovation officer at the Epilepsy Foundation.
“If you think about seizures as little brush fires in the brain, you want to put a blanket over or spray water on the fire. That’s what the phenobarbital does,” says Dr. French, who’s also a professor at NYU Langone Health’s Comprehensive Epilepsy Center in New York City.
Phenobarbital is not typically used as a first-line treatment for seizures anymore, says Megan Ehret, PharmD, an associate professor of pharmacy practice and science at the University of Maryland School of Pharmacy in Baltimore. “There are many newer medications, which may have fewer adverse effects and are better tolerated,” she says.
Still, in some cases phenobarbital does have its advantages. Arm yourself with the facts about the benefits versus the risks, and then have an honest conversation with your doctor. Is this the right treatment for you? Here’s what you need to know.
Phenobarbital has a very long half-life.
Quick biology refresher: Half-life refers to the amount of time it takes for half the medicine to disappear from your body. And as far as anti-seizure medications go, phenobarbital takes its sweet time.
“The half-life is up to 60 hours, which means that you can comfortably take it daily,” says Dr. French. “And even if you’re late on a dose or miss a dose, the level is not going to drop that much.” That’s especially beneficial for people who might not be able to remember to take a medication every day, Dr. French points out.
Phenobarbital tablets are very low cost.
Because it’s now completely generic (there’s not even a brand-name version anymore) it costs just pennies a day in some places, Dr. French says. That’s one reason why it’s a common choice in under-resourced countries, she adds.
Phenobarbital can be given with an IV.
When patients are hospitalized with severe, long-lasting seizures, an intravenous form of phenobarbital is often used. “It’s one of the few seizure medications that can be given by vein,” Dr. French says. “It’s a very strong and very effective medicine and quickly kicks in.” Though it’s an early treatment for an emergency, patients wouldn’t continue using it this way at home, she says.
Phenobarbital changes how your liver works.
Your liver processes nearly everything that comes into your body, and phenobarbital makes it work much faster. Sounds like a good thing, right? Not necessarily, Dr. French cautions.
“The problem is that we make all kinds of things in our body that are actually quite useful—hormones like estrogen and progesterone, for example. There’s a certain speed with which they need to leave, and phenobarbital causes them to leave too fast.”
And if you’re taking vitamins, birth control pills, or even other medications, they could get processed so quickly that they don’t have enough time to work.
Phenobarbital can be dangerous with alcohol.
With any prescription medication, alcohol is generally not recommended. But the combination with phenobarbital can be risky: Both substances slow your nervous system down, says Dr. French.
Phenobarbital can cause more serious problems if you come off of it too quickly.
“If you’ve been taking phenobarbital and then abruptly stop, you may experience more severe seizures than if you had never taken it to begin with,” Dr. French says. It could also produce serious “status epilepticus” seizures, which can be life-threatening, she says. If you need to stop taking phenobarbital, your doctor will wean you very slowly. It’s a process that takes at least several weeks.