Phenobarbital (fee-no-BAR-bih-tal) is a seizure medicine manufactured by several companies. It is the oldest epilepsy medicine still in use. In 1912, two independent teams of chemists created it under the name of Luminal.

The advantages of phenobarbital are its long history of use, low cost, and effectiveness. It stays in the body for a long time, so the amount of medicine in the blood stays fairly steady even if it is taken only once a day.

A disadvantage is that it makes many people sleepy and sometimes causes other changes in behavior. Not everyone is affected the same way, however, and many individuals do well when they take phenobarbital. Another problem is that after people take it for a while, they must be very careful if they want to stop taking it. They could have withdrawal seizures. The doctor will recommend a very slow reduction in the dose to prevent these seizures.

Forms
The same medicine is available in several forms because people's needs vary. The name or appearance may differ from country to country, or even from manufacturer to manufacturer, but usually the dose (measured in milligrams, abbreviated "mg") will be the same. In the United States, several companies sell phenobarbital, in these forms:

Tablets

	15-mg
	30-mg
	60-mg
	100-mg

Liquid (not shown): 20 mg per 5 mL (milliliters)

How to take and store phenobarbital
It's OK to take phenobarbital either with food or without food, but it's best to be consistent from day to day. Follow the doctor's directions. Call if you have any questions. The way the medicine is taken depends, of course, on what form the doctor has prescribed.

Phenobarbital is usually taken just once a day. Most people find that sleepiness is less of a problem during the day if they take the phenobarbital 30 to 60 minutes before bedtime.

If needed, tablets may be crushed and put in foods for children. A liquid (elixir) is available for those who cannot swallow pills, however. This liquid can be given with water, milk, or juice. Be sure to use the same standard-size medicine spoon or dropper each time to get an accurate dose.

If the doctor changes the amount of phenobarbital to be taken, you may be given a different form. For example, you may start out using 30-mg tablets and then switch to 60-mg tablets. If this happens, be careful to use the correct number. Don't automatically continue to use the same number of pills as before.

Store phenobarbital at room temperature, away from heat, direct light, and dampness. If you have the liquid form, prevent it from freezing. Be particularly careful to keep phenobarbital out of the reach of children, since overdose is especially dangerous for children.

Don't use more than the doctor prescribes. If one or two extra tablets or an extra spoonful of liquid are taken, call the doctor for advice. For a larger overdose, call your local poison control center or emergency room right away unless you have other specific directions from your doctor.

Don't stop using phenobarbital or change the amount taken without talking to the doctor first. Stopping any seizure medicine all at once can affect other medicines in the body. It may even cause nonstop seizures that can be life-threatening.

What if I forget?
Ask the doctor what to do if you forget a dose. In general, a forgotten dose should be taken right away, unless it is almost time for the next one. In that case, just use one dose—not a double dose—and call the doctor's office for more advice.

Do your best to follow the doctor's directions. If you forget doses often, it may be a good idea to get a special pillbox or watch with an alarm to remind you.

Taking the amount of seizure medicine the doctor prescribes and taking it at the right time every single day are the most important steps in preventing seizures!

Reviewed February 2004 by Steven C. Schachter, MD, epilepsy.com Editorial Board.