Phenobarbital (patient information)

Why is this medication prescribed
Phenobarbital, a barbiturate, is used to control epilepsy (seizures) and as a sedative to relieve anxiety. It is also used for short-term treatment of insomnia to help you fall asleep.

This medication is sometimes prescribed for other uses; ask your doctor or pharmacist for more information.

How should this medicine be used
Phenobarbital comes as a tablet, capsule, and elixir (liquid) to take by mouth. You may obtain a specially marked measuring spoon from your pharmacist to be sure of an accurate dose of the liquid. It usually is taken one to three times a day and may be taken with or without food. If you take phenobarbital once a day, take it at bedtime. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take phenobarbital exactly as directed. If you are taking phenobarbital to control convulsions or seizures, follow the exact schedule prescribed by your doctor.

Phenobarbital can be habit-forming. Do not use phenobarbital for more than 2 weeks if it is being used to help you sleep. Do not take a larger dose, take it more often, or for a longer time than your doctor tells you to. Tolerance may develop with long-term or excessive use, making the drug less effective. This medication must be taken regularly to be effective. Do not skip doses even if you feel that you do not need them. Call your doctor if you have convulsions or seizures while taking phenobarbital. Do not stop taking this drug without talking to your doctor, especially if you have been taking it for a long time. Stopping the drug suddenly can cause withdrawal symptoms (anxiousness, sleeplessness, and irritability). Your doctor probably will decrease your dose gradually.

What special precautions should I follow
Before taking phenobarbital:


 * tell your doctor and pharmacist if you are allergic to phenobarbital or any other drugs.
 * tell your doctor and pharmacist what prescription and nonprescription medications you are taking, especially acetaminophen (Tylenol); anticoagulants such as warfarin (Coumadin); carbamazepine (Tegretol); chloramphenicol (Chloromycetin); clonazepam (Klonopin); disulfiram (Antabuse); doxycycline (Vibramycin); felodipine (Plendil); fenoprofen (Nalfon); griseofulvin (Fulvicin); MAO inhibitors [phenelzine (Nardil) or tranylcypromine (Parnate)]; medications for depression, seizures, pain, asthma, colds, or allergies; metoprolol (Lopressor); metronidazole (Flagyl); muscle relaxants; phenylbutazone (Azolid, Butazolidin); propranolol (Inderal); quinidine; rifampin (Rifadin); sedatives; sleeping pills; steroids; theophylline (Theo-Dur); tranquilizers; valproic acid (Depakene); verapamil (Calan); and vitamins. These medications may add to the drowsiness caused by phenobarbital.
 * tell your doctor if you have or have ever had anemia or seizures, or lung, heart, or liver disease.
 * use a method of birth control other than oral contraceptives while taking this medication. Phenobarbital can decrease the effectiveness of oral contraceptives.
 * tell your doctor if you are pregnant, plan to become pregnant, or are breast-feeding. If you become pregnant while taking phenobarbital, call your doctor immediately.
 * if you are having surgery, including dental surgery, tell the doctor or dentist that you are taking phenobarbital.
 * you should know that this drug may make you drowsy. Do not drive a car or operate machinery until you know how this drug affects you.
 * remember that alcohol can add to the drowsiness caused by this drug.

What should I do if I forget a dose
If you take several doses per day, take the missed dose as soon as you remember it and take any remaining doses for that day at evenly spaced intervals. However, if it is almost time for the next dose, skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make up for a missed one.

Mild side effects
Side effects from phenobarbital may occur and include:


 * drowsiness
 * headache
 * dizziness
 * depression
 * excitement (especially in children)
 * upset stomach
 * vomiting

Tell your doctor if any of these symptoms are severe or do not go away:


 * nightmares
 * increased dreaming
 * constipation
 * joint or muscle pain

Severe side effects
If you experience any of the following symptoms, call your doctor immediately:


 * seizures
 * mouth sores
 * sore throat
 * easy bruising
 * bloody nose
 * unusual bleeding
 * fever
 * difficulty breathing or swallowing
 * severe skin rash

If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration's (FDA) MedWatch Adverse Event Reporting program online [at http://www.fda.gov/MedWatch/report.htm] or by phone [1-800-332-1088].

What storage conditions are needed for this medicine
Keep this medication in the container it came in, tightly closed, and out of reach of children. Store it at room temperature and away from excess heat and moisture (not in the bathroom). Throw away any medication that is outdated or no longer needed. Talk to your pharmacist about the proper disposal of your medication.

In case of emergency/overdose
In case of overdose, call your local poison control center at 1-800-222-1222. If the victim has collapsed or is not breathing, call local emergency services at 911.

What other information should I know
Keep all appointments with your doctor and the laboratory. Your doctor will order certain lab tests to check your response to phenobarbital.

If you are taking phenobarbital to control seizures and have an increase in their frequency or severity, call your doctor. Your dose may need to be adjusted. If you use phenobarbital for seizures, carry identification (Medic Alert) stating that you have epilepsy and that you are taking phenobarbital.

Do not let anyone else take your medication. Ask your pharmacist any questions you have about refilling your prescription.

Brand names

 * Luminal® Sodium