Generic Name: Phenobarbital

  • What is Phenobarbital?

    Phenobarbital, a barbiturate, is used to treat certain types of seizures. It is also used for sedation.

  • What is the most important information I should know about Phenobarbital?

    Phenobarbital can be habit-forming. You may become tolerant and need more of the drug to achieve the same effect. You may become physically and psychologically dependent with continued use. Never increase the amount of phenobarbital you take without checking with your doctor.

    Phenobarbital may cause excitement, depression, or confusion in elderly or weakened individuals, and excitement in children.

    Barbiturates such as phenobarbital may cause you to become tired or less alert. Be careful driving, operating machinery, or doing any activity that requires full mental alertness until you know how this medication affects you.

  • Who should not take Phenobarbital?

    Phenobarbital should not be used if you suffer from porphyria (a blood disorder), liver or lung disease, or if you have ever had an allergic reaction to or are sensitive to phenobarbital or other barbiturates.

    Phenobarbital should be used with extreme caution, or not at all, by people who are depressed or who have a history of drug or alcohol dependence.

  • What should I tell my doctor before I take the first dose of Phenobarbital?

    Tell your doctor about all prescription, over-the-counter, and herbal medications you are taking before beginning treatment with phenobarbital. Also, talk to your doctor about your complete medical history, especially if you have a history of depression, suicidal thoughts, drug or alcohol dependence, liver disease, adrenal gland problems, and constant pain.

  • What is the usual dosage?

    The information below is based on the dosage guidelines your doctor uses. Depending on your condition and medical history, your doctor may prescribe a different regimen. Do not change the dosage or stop taking your medication without your doctor's approval.


    Adults: The usual dose is 30-120 milligrams (mg) a day. The number of times you take phenobarbital a day will be determined by your response to it.


    Adults: Your doctor will determine the exact dose best for you, based on specific laboratory tests. The typical doses are 50-100 mg taken two to three times daily.

    Children: Your doctor will determine the exact dose best for your child, based on specific laboratory tests.

    Elderly, debilitated, or patients who have liver or kidney disease may require a lower dose of phenobarbital.

    Your dosing might be different from what's listed above since there are other forms of phenobarbital available. Your doctor will determine the exact dose that you will need.

  • How should I take Phenobarbital?

    Take this medication exactly as prescribed by your doctor. You should never stop taking phenobarbital without consulting your doctor first, especially if you are using this medication for seizures.

  • What should I avoid while taking Phenobarbital?

    Avoid driving, operating machinery, or doing any activity that requires full mental alertness until you know how this medication affects you.

    Do not drink alcohol or take other central nervous system (CNS) depressants (such as narcotics, tranquilizers, and antihistamines) while on phenobarbital. They may intensify the CNS-depressant effects.

  • What are possible food and drug interactions associated with Phenobarbital?

    If phenobarbital is taken with certain other drugs, the effects of either could be increased, decreased, or altered. It is especially important to check with your doctor before combining this medication with any of the following: antidepressants known as monoamine oxidase inhibitors (MAOIs), antihistamines, blood thinners (such as warfarin), corticosteroids, doxycycline, seizure drugs, griseofulvin, narcotic pain relievers, birth control pills, phenytoin, sedatives, steroidal hormones (such as progesterone, estrone), tranquilizers, or valproic acid.

  • What are the possible side effects of Phenobarbital?

    Side effects cannot be anticipated. If any develop or change in intensity, tell your doctor as soon as possible. Only your doctor can determine if it is safe for you to continue taking this drug.

    Side effects may include: allergic reactions, drowsiness, headache, fatigue, nausea, oversedation, sleepiness, slowed or delayed breathing, dizziness, vomiting

  • Can I receive Phenobarbital if I am pregnant or breastfeeding?

    Barbiturates such as phenobarbital may harm your unborn baby. If you are pregnant or plan to become pregnant, inform your doctor immediately.

    Phenobarbital is excreted in breast milk. Talk to your doctor about whether you should stop breastfeeding while taking this medication.

  • What should I do if I miss a dose of Phenobarbital?

    If you miss a dose of phenobarbital, take it as soon as you remember. If it is almost time for your next dose, skip the one you missed and go back to your regular dosing schedule. Do not take two doses at once.

  • How should I store Phenobarbital?

    Store at room temperature.

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