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Phenobarbital (By mouth)

Phenobarbital (fee-noe-BAR-bi-tal)

Treats seizures. Also may be used as a sedative.

Brand Name(s):

PHENobarbital AvPak

There may be other brand names for this medicine.

When This Medicine Should Not Be Used:

You should not use this medicine if you have had an allergic reaction to phenobarbital or other barbiturate drugs, such as pentobarbital, amobarbital, or secobarbital. You should not use if you are pregnant or breastfeeding, if you have porphyria, or if you have severe lung or liver disease.

How to Use This Medicine:

Tablet, Capsule, Liquid

  • Your doctor will tell you how much to take and how often.
  • It is best to take this medicine on an empty stomach.

If a dose is missed:

  • Take the missed dose as soon as possible.
  • Skip the missed dose if it is almost time for your next dose.
  • You should not use two doses at the same time.

How to Store and Dispose of This Medicine:

  • Store at room temperature, away from heat, direct light, and moisture.
  • Ask your pharmacist, doctor, or health caregiver about the best way to dispose of any outdated medicine or medicine no longer needed.
  • Keep all medicine away from children.

Drugs and Foods to Avoid:

Ask your doctor or pharmacist before using any other medicine, including over-the-counter medicines, vitamins, and herbal products.

  • Avoid drinking alcohol.
  • Avoid taking other medicines that make you sleepy, such as sleeping pills, sedatives, or cold or allergy medicines while taking phenobarbital.
  • Before taking this medicine, make sure your doctor knows if you are taking blood thinners (Coumadin®), corticosteroids, phenytoin (Dilantin®), valproic acid (Depakane®), doxycycline, or griseofulvin.
  • Birth control pills may not work if you take them while taking phenobarbital. Use another form of birth control while taking this medicine.

Warnings While Using This Medicine:

  • Check with your doctor before taking if you are pregnant, breastfeeding, or are planning to become pregnant, or if you have any type of lung disease, asthma, or liver disease.
  • If you are using this medicine regularly, do not stop taking it suddenly without first asking your doctor. You may need to take less and less before stopping completely.
  • You should not use more of this medicine or take it for longer periods than your doctor has ordered. Phenobarbital can be habit-forming.
  • This medicine can make you drowsy. Be careful when driving or operating machinery.

Possible Side Effects While Using This Medicine:

Call your doctor right away if you notice any of these side effects:

  • Hives or severe skin rash
  • Swelling of eyelids or face
  • Severe drowsiness, confusion, or slurred speech
  • Shortness of breath or trouble breathing
  • Uncontrollable eye movements
  • Yellowing of eyes or skin
  • Hallucinations

If you notice these less serious side effects, talk with your doctor:

  • Drowsiness, dizziness, unsteadiness, "hangover" effects, trouble concentrating
  • Nausea, vomiting
  • Depressed mood
  • Constipation
  • Irritability, nervousness or excitement

If you notice other side effects that you think are caused by this medicine, tell your doctor

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088

Last Updated: 1/7/2020

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